American Lung Association v. EPA ( 2021 )


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  •  United States Court of Appeals
    FOR THE DISTRICT OF COLUMBIA CIRCUIT
    Argued October 8, 2020              Decided January 19, 2021
    No. 19-1140
    AMERICAN LUNG ASSOCIATION AND AMERICAN PUBLIC
    HEALTH ASSOCIATION,
    PETITIONERS
    v.
    ENVIRONMENTAL PROTECTION AGENCY AND ANDREW
    WHEELER, ADMINISTRATOR,
    RESPONDENTS
    AEP GENERATING COMPANY, ET AL.,
    INTERVENORS
    Consolidated with 19-1165, 19-1166, 19-1173, 19-1175,
    19-1176, 19-1177, 19-1179, 19-1185, 19-1186, 19-1187,
    19-1188
    On Petitions for Review of a Final Action
    of the Environmental Protection Agency
    Steven C. Wu, Deputy Solicitor General, Office of the
    Attorney General for the State of New York, argued the cause
    for the State and Municipal petitioners and intervenor Nevada.
    2
    With him on the briefs were Letitia James, Attorney General,
    Barbara D. Underwood, Solicitor General, Matthew W.
    Grieco, Assistant Solicitor General, Michael J. Myers, Senior
    Counsel, Andrew G. Frank, Assistant Attorney General of
    Counsel, Xavier Becerra, Attorney General, Office of the
    Attorney General for the State of California, Robert W. Byrne,
    Senior Assistant Attorney General, David A. Zonana,
    Supervising Deputy Attorney General, Jonathan A. Wiener, M.
    Elaine Meckenstock, Timothy E. Sullivan, Elizabeth B. Rumsey,
    and Theodore A.B. McCombs, Deputy Attorneys General,
    William Tong, Attorney General, Office of the Attorney
    General for the State of Connecticut, Matthew I. Levine and
    Scott N. Koschwitz, Assistant Attorneys General, Kathleen
    Jennings, Attorney General, Office of the Attorney General for
    the State of Delaware, Valerie S. Edge, Deputy Attorney
    General, Philip J. Weiser, Attorney General, Office of the
    Attorney General for the State of Colorado, Eric R. Olson,
    Solicitor General, Robyn L. Wille, Senior Assistant Attorney
    General, Clare E. Connors, Attorney General, Office of the
    Attorney General for the State of Hawaii, William F. Cooper,
    Deputy Attorney General, Aaron M. Frey, Attorney General,
    Office of the Attorney General for the State of Maine, Laura
    E. Jensen, Assistant Attorney General, Brian E. Frosh,
    Attorney General, Office of the Attorney General for the State
    of Maryland, John B. Howard, Jr., Joshua M. Segal, and
    Steven J. Goldstein, Special Assistant Attorneys General,
    Maura Healey, Attorney General, Office of the Attorney
    General for the Commonwealth of Massachusetts, Melissa A.
    Hoffer and Christophe Courchesne, Assistant Attorneys
    General, Megan M. Herzog and David S. Frankel, Special
    Assistant Attorneys General, Dana Nessel, Attorney General,
    Office of the Attorney General for the State of Michigan,
    Gillian E. Wener, Assistant Attorney General, Keith Ellison,
    Attorney General, Office of the Attorney General for the State
    of Minnesota, Peter N. Surdo, Special Assistant Attorney
    3
    General, Aaron D. Ford, Attorney General, Office of the
    Attorney General for the State of Nevada, Heidi Parry Stern,
    Solicitor General, Gurbir S. Grewal, Attorney General, Office
    of the Attorney General for the State of New Jersey, Lisa J.
    Morelli, Deputy Attorney General, Hector Balderas, Attorney
    General, Office of the Attorney General for the State of New
    Mexico, Tania Maestas, Chief Deputy Attorney General,
    Joshua H. Stein, Attorney General, Office of the Attorney
    General for the State of North Carolina, Asher Spiller,
    Assistant Attorney General, Ellen F. Rosenblum, Attorney
    General, Office of the Attorney General for the State of
    Oregon, Paul Garrahan, Attorney-in-Charge, Steve Novick,
    Special Assistant Attorney General, Josh Shapiro, Attorney
    General, Office of the Attorney General for the
    Commonwealth of Pennsylvania, Ann R. Johnston, Senior
    Deputy Attorney General, Aimee D. Thomson, Deputy
    Attorney General, Peter F. Neronha, Attorney General, Office
    of the Attorney General for the State of Rhode Island, Gregory
    S. Schultz, Special Assistant Attorney General, Thomas J.
    Donovan, Jr., Attorney General, Office of the Attorney
    General for the State of Vermont, Nicholas F. Persampieri,
    Assistant Attorney General, Mark Herring, Attorney General,
    Office of the Attorney General for the Commonwealth of
    Virginia, Donald D. Anderson, Deputy Attorney General, Paul
    Kugelman, Jr., Senior Assistant Attorney General and Chief,
    Environmental Section, Caitlin Colleen Graham O=Dwyer,
    Assistant Attorney General, Robert W. Ferguson, Attorney
    General, Office of the Attorney General for the State of
    Washington, Christopher H. Reitz and Emily C. Nelson,
    Assistant Attorneys General, Joshua L. Kaul, Attorney
    General, Office of the Attorney General for the State of
    Wisconsin, Gabe Johnson-Karp, Assistant Attorney General,
    Karl A. Racine, Attorney General, Office of the Attorney
    General for the District of Columbia, Loren L. AliKhan,
    Solicitor General, Tom Carr, City Attorney, Office of the City
    4
    Attorney for the City of Boulder, Debra S. Kalish, Senior
    Counsel, Mark A. Flessner, Corporation Counsel, Office of the
    Corporation Counsel for the City of Chicago, Benna Ruth
    Solomon, Deputy Corporation Counsel, Jared Policicchio,
    Supervising Assistant Corporation Counsel, Kristin M.
    Bronson, City Attorney, Office of the City Attorney for the
    City and County of Denver, Lindsay S. Carder and Edward J.
    Gorman, Assistant City Attorneys, Michael N. Feuer, City
    Attorney, Office of the City Attorney for the City of Los
    Angeles, Michael J. Bostrom, Assistant City Attorney, James
    E. Johnson, Corporation Counsel, New York City Law
    Department, Christopher G. King, Senior Counsel, Marcel S.
    Pratt, City Solicitor, City of Philadelphia Law Department,
    Scott J. Schwarz and Patrick K. O’Neill, Divisional Deputy
    City Solicitors, and Thomas F. Pepe, City Attorney, City of
    South Miami. Morgan A. Costello and Brian M. Lusignan,
    Assistant Attorneys General, Office of the Attorney General
    for the State of New York, Gavin G. McGabe, Deputy Attorney
    General, Anne Minard, Special Assistant Attorney General,
    Office of the Attorney General for the State of New Mexico,
    Cynthia M. Weisz, Assistant Attorney General, Office of the
    Attorney General for the State of Maryland, entered
    appearances.
    Kevin Poloncarz argued the cause for Power Company
    Petitioners. With him on the briefs were Donald L. Ristow and
    Jake Levine.
    Mark W. DeLaquil argued the cause for Coal Industry
    Petitioners. With him on the briefs were Shay Dvoretzky,
    Charles T. Wehland, Jeffery D. Ubersax, Robert D. Cheren,
    and Andrew Grossman.
    5
    Theodore Hadzi-Antich argued the cause for Robinson
    Enterprises Petitioners. With him on the briefs were Robert
    Henneke and Ryan D. Walters.
    Sean H. Donahue and Michael J. Myers argued the causes
    for Public Health and Environmental Petitioners. On the briefs
    were Ann Brewster Weeks, James P. Duffy, Susannah L.
    Weaver, Joanne Spalding, Andres Restrepo, Vera Pardee,
    Clare Lakewood, Howard M. Crystal, Elizabeth Jones,
    Brittany E. Wright, Jon A. Mueller, David Doniger, Benjamin
    Longstreth, Melissa J. Lynch, Lucas May, Vickie L. Patton,
    Tomas Carbonell, Benjamin Levitan, Howard Learner, and
    Scott Strand. Alejandra Nunez entered an appearance.
    David M. Williamson argued the cause and filed the briefs
    for Biogenic Petitioners.
    Gene Grace, Jeff Dennis, and Rick Umoff were on the brief
    for petitioners American Wind Energy Association, et al.
    Theodore E. Lamm and Sean B. Hecht were on the brief
    for amicus curiae Thomas C. Jorling in support of petitioners.
    Gabriel Pacyniak, Brent Chapman, and Graciela Esquivel
    were on the brief for amici curiae the Coalition to Protect
    America=s National Parks and the National Parks Conservation
    Association in support of petitioners.
    Deborah A. Sivas and Matthew J. Sanders were on the
    brief for amici curiae Administrative Law Professors in
    support of petitioners.
    Hope M. Babcock was on the brief for amici curiae the
    American Thoracic Society, et al. in support of petitioners.
    6
    Richard L. Revesz and Jack Lienke were on the brief for
    amicus curiae the Institute for Policy Integrity at New York
    University School of Law in support of petitioners.
    Steph Tai was on the brief for amici curiae Climate
    Scientists in support of petitioners.
    Michael Burger and Collyn Peddie were on the brief for
    amici curiae the National League of Cities, et al. in support of
    petitioners.
    Keri R. Steffes was on the brief for amici curiae Faith
    Organizations in support of petitioners.
    Shaun A. Goho was on the brief for amici curiae
    Maximilian Auffhammer, et al. in support of petitioners.
    Ethan G. Shenkman and Stephen K. Wirth were on the
    brief for amici curiae Patagonia Works and Columbia
    Sportswear Company in support of petitioners.
    Mark Norman Templeton, Robert Adam Weinstock,
    Alexander Valdes, and Benjamin Nickerson were on the brief
    for amicus curiae Professor Michael Greenstone in support of
    petitioners.
    Nicole G. Berner and Renee M. Gerni were on the brief for
    amicus curiae the Service Employees International Union in
    support of petitioners.
    Elizabeth B. Wydra, and Brianne J. Gorod were on the
    brief for amici curiae Members of Congress in support of
    petitioners.
    7
    Jonas J. Monast was on the brief for amici curiae Energy
    Modelers in support of petitioners.
    Katherine Konschnik was on the brief for amici curiae
    Former Commissioners of the Federal Energy Regulatory
    Commission in support of petitioners.
    Michael Landis, Elizabeth S. Merritt, and Wyatt G.
    Sassman were on the brief for amici curiae Environment
    America and National Trust for Historic Preservation in
    support of petitioners.
    Cara A. Horowitz was on the brief for amici curiae Grid
    Experts in support of petitioners.
    Eric Alan Isaacson was on the brief for amici curiae U.S.
    Senators in support of petitioners.
    Jonathan D. Brightbill, Principal Deputy Assistant
    Attorney General, U.S. Department of Justice, and Meghan E.
    Greenfield and Benjamin Carlisle, Attorneys, argued the
    causes for respondents. With them on the brief was Jeffrey
    Bossert Clark, Assistant Attorney General.
    Lindsay S. See, Solicitor General, Office of the Attorney
    General for the State of West Virginia, argued the cause for
    State and Industry intervenors in support of respondents
    regarding Affordable Clean Energy Rule. With her on the brief
    were Patrick Morrisey, Attorney General, Thomas T.
    Lampman, Assistant Solicitors General, Thomas A. Lorenzen,
    Elizabeth B. Dawson, Rae Cronmiller, Kevin G. Clarkson,
    Attorney General at the time the brief was filed, Office of the
    Attorney General for the State of Alaska, Clyde Sniffen Jr.,
    Attorney General, Leslie Rutledge, Attorney General, Office of
    the Attorney General for the State of Arkansas, Nicholas J.
    8
    Bronni, Solicitor General, Vincent M. Wagner, Deputy
    Solicitor General, Dylan L. Jacobs, Assistant Solicitor General,
    Steve Marshall, Attorney General, Office of the Attorney
    General for the State of Alabama, Edmund G. LaCour, Jr.,
    Solicitor General, Christopher M. Carr, Attorney General,
    Office of the Attorney General for the State of Georgia,
    Andrew A. Pinson, Solicitor General, Derek Schmidt, Attorney
    General, Office of the Attorney General for the State of Kansas,
    Jeffrey A. Chanay, Chief Deputy Attorney General, Curtis T.
    Hill, Jr., Attorney General, Office of the Attorney General of
    Indiana, Thomas M. Fisher, Solicitor General, Andrew
    Beshear, Governor, Office of the Governor for the
    Commonwealth of Kentucky, S. Travis Mayo, Chief Deputy
    General Counsel, Taylor Payne, Deputy General Counsel,
    Joseph A. Newberg, Deputy General Counsel and Deputy
    Executive Director, Jeff Landry, Attorney General, Office of
    the Attorney General for the State of Louisiana, Elizabeth B.
    Murrill, Solicitor General, Harry J. Vorhoff, Assistant
    Attorney General, Eric S. Schmitt, Attorney General, Office of
    the Attorney General for the State of Missouri, D. John Sauer,
    Solicitor General, Julie Marie Blake, Deputy Solicitor General,
    Timothy C. Fox, Attorney General at the time the brief was
    filed, Office of the Attorney General for the State of Montana,
    Matthew T. Cochenour, Deputy Solicitor General, Wayne
    Stenehjem, Attorney General, Office of the Attorney General
    for the State of North Dakota, Paul M. Seby, Special Assistant
    Attorney General, Douglas J. Peterson, Attorney General,
    Office of the Attorney General for the State of Nebraska, Justin
    D. Lavene, Assistant Attorney General, Dave Yost, Attorney
    General, Office of the Attorney General of the State of Ohio,
    Benjamin M. Flowers, Solicitor General, Cameron F.
    Simmons, Principal Assistant Attorney General, Mike Hunter,
    Attorney General, Office of the Attorney General for the State
    of Oklahoma, Mithun Mansinghani, Solicitor General, Jason
    R. Ravnsborg, Attorney General, Office of the Attorney
    9
    General for the State of South Dakota, Steven R. Blair,
    Assistant Attorney General, Alan Wilson, Attorney General,
    Office of the Attorney General for the State of South Carolina,
    James Emory Smith, Jr., Deputy Solicitor General, Ken
    Paxton, Attorney General, Office of the Attorney General for
    the State of Texas, Kyle D. Hawkins, Solicitor General, Sean
    Reyes, Attorney General, Office of the Attorney General for the
    State of Utah, Tyler R. Green, Solicitor General, Bridget Hill,
    Attorney General, Office of the Attorney General for the State
    of Wyoming, James Kaste, Deputy Attorney General, Todd E.
    Palmer, William D. Booth, Obianuju Okasi, Carroll W.
    McGuffey, III, Misha Tseytlin, C. Grady Moore, III, Julia
    Barber, F. William Brownell, Elbert Lin, Allison D. Wood,
    Scott A. Keller, Jeffrey H. Wood, Jeremy Evan Maltz, Steven P.
    Lehotsky, Michael B. Schon, Emily Church Schilling, Kristina
    R. Van Bockern, David M. Flannery, Kathy G. Beckett, Edward
    L. Kropp, Amy M. Smith, Janet J. Henry, Melissa Horne,
    Angela Jean Levin, Eugene M. Trisko, John A. Rego, Reed W.
    Sirak, Michael A. Zody, Jacob Santini, Robert D. Cheren, Mark
    W. DeLaquil, and Andrew M. Grossman. C. Frederick Beckner,
    III, James R. Bedell, Margaret C. Campbell, Erik D. Lange,
    and John D. Lazzaretti entered an appearance.
    James P. Duffy argued the cause for Public Health and
    Environmental Intervenors in support of respondents. With
    him on the brief were Ann Brewster Weeks, Sean H. Donahue,
    Susannah L. Weaver, Joanne Spalding, Andres Restrepo, Vera
    Pardee, Clare Lakewood, Elizabeth Jones, Brittany E. Wright,
    Jon A. Mueller, David Doniger, Benjamin Longstreth, Melissa
    J. Lynch, Lucas May, Vickie L. Patton, Tomas Carbonell,
    Benjamin Levitan, Howard Learner, and Scott Strand.
    Letitia James, Attorney General, Office of the Attorney
    General for the State of New York, Michael J. Myers, Senior
    Counsel, Brian Lusignan, Assistant Attorney General of
    10
    Counsel, Barbara D. Underwood, Solicitor General, Steven C.
    Wu, Deputy Solicitor General, Matthew W. Grieco, Assistant
    Solicitor General, Xavier Becerra, Attorney General, Office of
    the Attorney General for the State of California, Robert W.
    Byrne, Senior Assistant Attorney General, David A. Zonana,
    Supervising Deputy Attorney General, Jonathan A. Wiener, M.
    Elaine Meckenstock, Timothy E. Sullivan, Elizabeth B. Rumsey,
    and Theodore A.B. McCombs, Deputy Attorneys General,
    William Tong, Attorney General, Office of the Attorney
    General for the State of Connecticut, Matthew I. Levine and
    Scott N. Koschwitz, Assistant Attorneys General, Kathleen
    Jennings, Attorney General, Office of the Attorney General for
    the State of Delaware, Valerie S. Edge, Deputy Attorney
    General, Philip J. Weiser, Attorney General, Office of the
    Attorney General for the State of Colorado, Eric R. Olson,
    Solicitor General, Robyn L. Wille, Senior Assistant Attorney
    General, Clare E. Connors, Attorney General, Office of the
    Attorney General for the State of Hawaii, William F. Cooper,
    Deputy Attorney General, Aaron M. Frey, Attorney General,
    Office of the Attorney General for the State of Maine, Laura
    E. Jensen, Assistant Attorney General, Brian E. Frosh,
    Attorney General, Office of the Attorney General for the State
    of Maryland, John B. Howard, Jr., Joshua M. Segal, and Steven
    J. Goldstein, Special Assistant Attorneys General, Maura
    Healey, Attorney General, Office of the Attorney General for
    the Commonwealth of Massachusetts, Melissa A. Hoffer and
    Christophe Courchesne, Assistant Attorneys General, Megan
    M. Herzog and David S. Frankel, Special Assistant Attorneys
    General, Dana Nessel, Attorney General, Office of the
    Attorney General for the State of Michigan, Gillian E. Wener,
    Assistant Attorney General, Keith Ellison, Attorney General,
    Office of the Attorney General for the State of Minnesota,
    Peter N. Surdo, Special Assistant Attorney General, Aaron D.
    Ford, Attorney General, Office of the Attorney General for the
    State of Nevada, Heidi Parry Stern, Solicitor General, Gurbir
    11
    S. Grewal, Attorney General, Office of the Attorney General
    for the State of New Jersey, Lisa J. Morelli, Deputy Attorney
    General, Hector Balderas, Attorney General, Office of the
    Attorney General for the State of New Mexico, Tania Maestas,
    Chief Deputy Attorney General, Joshua H. Stein, Attorney
    General, Office of the Attorney General for the State of North
    Carolina, Asher Spiller, Assistant Attorney General, Ellen F.
    Rosenblum, Attorney General, Office of the Attorney General
    for the State of Oregon, Paul Garrahan, Attorney-in-Charge,
    Steve Novick, Special Assistant Attorney General, Josh
    Shapiro, Attorney General, Office of the Attorney General for
    the Commonwealth of Pennsylvania, Ann R. Johnston, Senior
    Deputy Attorney General, Aimee D. Thomson, Deputy
    Attorney General, Peter F. Neronha, Attorney General, Office
    of the Attorney General for the State of Rhode Island, Gregory
    S. Schultz, Special Assistant Attorney General, Thomas J.
    Donovan, Jr., Attorney General, Office of the Attorney
    General for the State of Vermont, Nicholas F. Persampieri,
    Assistant Attorney General, Mark Herring, Attorney General,
    Office of the Attorney General for the Commonwealth of
    Virginia, Donald D. Anderson, Deputy Attorney General, Paul
    Kugelman, Jr., Senior Assistant Attorney General and Chief,
    Environmental Section, Caitlin Colleen Graham O=Dwyer,
    Assistant Attorney General, Robert W. Ferguson, Attorney
    General, Office of the Attorney General for the State of
    Washington, Christopher H. Reitz and Emily C. Nelson,
    Assistant Attorneys General, Karl A. Racine, Attorney
    General, Office of the Attorney General for the District of
    Columbia, Loren L. AliKhan, Solicitor General, Tom Carr,
    City Attorney, Office of the City Attorney for the City of
    Boulder, Debra S. Kalish, Senior Counsel, Mark A. Flessner,
    Corporation Counsel, Office of the Corporation Counsel for the
    City of Chicago, Benna Ruth Solomon, Deputy Corporation
    Counsel, Jared Policicchio, Supervising Assistant Corporation
    Counsel, Kristin M. Bronson, City Attorney, Office of the City
    12
    Attorney for the City and County of Denver, Lindsay S. Carder
    and Edward J. Gorman, Assistant City Attorneys, Michael N.
    Feuer, City Attorney, Office of the City Attorney for the City
    of Los Angeles, Michael J. Bostrom, Assistant City Attorney,
    James E. Johnson, Corporation Counsel, New York City Law
    Department, Christopher G. King, Senior Counsel, Marcel S.
    Pratt, City Solicitor, City of Philadelphia Law Department,
    Scott J. Schwarz and Patrick K. O’Neill, Divisional Deputy
    City Solicitors, and Thomas F. Pepe, City Attorney, City of
    South Miami were on the brief for the State and Municipal
    Intervenors in support of respondents. Jeremiah Langston,
    Assistant Attorney General, Office of the Attorney General for
    the State of Montana, Stephen C. Meredith, Solicitor, Office of
    the Attorney General for the Commonwealth of Kentucky,
    Margaret I. Olson, Assistant Attorney General, Office of the
    Attorney General for the State of North Dakota, and Erik E.
    Petersen, Assistant Attorney General, Office of the Attorney
    General for the State of Wyoming, and Robert A. Wolf entered
    appearances.
    Patrick Morrisey, Attorney General, Office of the
    Attorney General for the State of West Virginia, Lindsay S.
    See, Solicitor General, Thomas T. Lampman, Assistant
    Solicitor General, Scott A. Keller, Jeffrey H. Wood, Jeremy
    Evan Maltz, Steven P. Lehotsky, Michael B. Schon, Thomas A.
    Lorenzen, Elizabeth B. Dawson, Rae Cronmiller, Steve
    Marshall, Attorney General, Office of the Attorney General for
    the State of Alabama, Edmund G. LaCour, Jr., Solicitor
    General, Kevin G. Clarkson, Attorney General, Office of the
    Attorney General for the State of Alaska at the time the brief
    was filed, Clyde Sniffen, Jr., Attorney General, Leslie Rutledge,
    Attorney General, Office of the Attorney General for the State
    of Arkansas, Nicholas J. Bronni, Solicitor General, Vincent M.
    Wagner, Deputy Solicitor General, Dylan L. Jacobs, Assistant
    Solicitor General, Christopher M. Carr, Attorney General,
    13
    Office of the Attorney General for the State of Georgia,
    Andrew A. Pinson, Solicitor General, Derek Schmidt, Attorney
    General, Office of the Attorney General for the State of Kansas,
    Jeffrey A. Chanay, Chief Deputy Attorney General, Curtis T.
    Hill, Jr., Attorney General, Office of the Attorney General of
    Indiana, Thomas M. Fisher, Solicitor General, Andrew
    Beshear, Governor, Office of the Governor for the
    Commonwealth of Kentucky, S. Travis Mayo, Chief Deputy
    General Counsel, Taylor Payne, Deputy General Counsel,
    Joseph A. Newberg, Deputy General Counsel and Deputy
    Executive Director, Jeff Landry, Attorney General, Office of
    the Attorney General for the State of Louisiana, Elizabeth B.
    Murrill, Solicitor General, Harry J. Vorhoff, Assistant
    Attorney General, Eric S. Schmitt, Attorney General, Office of
    the Attorney General for the State of Missouri, D. John Sauer,
    Solicitor General, Julie Marie Blake, Deputy Solicitor General,
    Timothy C. Fox, Attorney General at the time the brief was
    filed, Office of the Attorney General for the State of Montana,
    Matthew T. Cochenour, Deputy Solicitor General, Wayne
    Stenehjem, Attorney General, Office of the Attorney General
    for the State of North Dakota, Paul M. Seby, Special Assistant
    Attorney General, Douglas J. Peterson, Attorney General,
    Office of the Attorney General for the State of Nebraska, Justin
    D. Lavene, Assistant Attorney General, Dave Yost, Attorney
    General, Office of the Attorney General of the State of Ohio,
    Benjamin M. Flowers, Solicitor General, Cameron F.
    Simmons, Principal Assistant Attorney General, Mike Hunter,
    Attorney General, Office of the Attorney General for the State
    of Oklahoma, Mithun Mansinghani, Solicitor General, Jason
    R. Ravnsborg, Attorney General, Office of the Attorney
    General for the State of South Dakota, Steven R. Blair,
    Assistant Attorney General, Alan Wilson, Attorney General,
    Office of the Attorney General for the State of South Carolina,
    James Emory Smith, Jr., Deputy Solicitor General, Ken
    Paxton, Attorney General, Office of the Attorney General for
    14
    the State of Texas, Kyle D. Hawkins, Solicitor General, Sean
    Reyes, Attorney General, Office of the Attorney General for the
    State of Utah, Tyler R. Green, Solicitor General, Bridget Hill,
    Attorney General, Office of the Attorney General for the State
    of Wyoming, James Kaste, Deputy Attorney General, Todd E.
    Palmer, William D. Booth, Obianuju Okasi, Carroll W.
    McGuffey, III, Misha Tseytlin, C. Grady Moore, III, Julia
    Barber, F. William Brownell, Elbert Lin, Allison D. Wood,
    Emily Church Schilling, Kristina R. Van Bockern, David M.
    Flannery, Kathy G. Beckett, Edward L. Kropp, Amy M. Smith,
    Janet J. Henry, Melissa Horne, Angela Jean Levin, Eugene M.
    Trisko, John A. Rego, Reed W. Sirak, Michael A. Zody, Jacob
    Santini, Robert D. Cheren, Mark W. DeLaquil, and Andrew M.
    Grossman were on the brief for State and Industry Intervenors
    in support of respondents regarding Clean Power Plan Repeal.
    Wayne Stenehjem, Attorney General, Office of the
    Attorney General for the State of North Dakota, and Paul M.
    Seby, Special Assistant Attorney General, were on the brief for
    intervenor State of North Dakota in support of the respondents.
    Jerry Stouck entered an appearance.
    Thomas J. Ward, Megan H. Berge, and Jared R. Wigginton
    were on the brief for amicus curiae National Association of
    Builders in support of respondents.
    Before: MILLETT , PILLARD , and WALKER, Circuit Judges.
    Opinion for the Court filed PER CURIAM.
    Opinion concurring in part, concurring in the judgment in
    part, and dissenting in part filed by Circuit Judge WALKER.
    15
    TABLE OF C ONTENTS
    I. Background .........................................................................17
    A. The Clean Air Act ..........................................................17
    B. Electricity and Climate Change .....................................21
    1. Electricity.....................................................................21
    2. Climate Change and the Federal Government ..........24
    C. The Clean Power Plan ....................................................29
    D. The ACE Rule ................................................................32
    1. Repeal of the Clean Power Plan .................................32
    2. Best System of Emission Reduction ..........................33
    3. Degree of Emission Limitation Achievable ..............36
    4. Implementing Regulations..........................................38
    E. Petitions for Review .......................................................38
    F. Jurisdiction and Standard of Review .............................39
    II. Section 7411 .......................................................................40
    A. Statutory Context............................................................40
    1. Text ..............................................................................46
    2. Statutory History, Structure, and Purpose .................59
    3. Compliance Measures .................................................71
    B. The Major Questions Doctrine ......................................74
    1. The EPA’s Regulatory Mandate ................................75
    2. Best System of Emission Reduction ..........................80
    C. Federalism .......................................................................92
    III. The EPA’s Authority to Regulate Carbon Dioxide
    Emissions Under Section 7411 ..............................................98
    A. The Coal Petitioners’ Challenges ..................................98
    1. Endangerment Finding................................................99
    2. Section 7411 and Section 7412’s
    Parallel Operation...................................................... 111
    B. The Robinson Petitioners’ Challenges ....................... 132
    IV. Amendments to the Implementing Regulations ...... 138
    V. Vacatur and Remand .................................................... 146
    VI. Conclusion ..................................................................... 147
    16
    As the Supreme Court recognized nearly fourteen years
    ago, climate change has been called “the most pressing
    environmental challenge of our time.” Massachusetts v. EPA,
    
    549 U.S. 497
    , 505 (2007) (formatting modified). Soon
    thereafter, the United States government determined that
    greenhouse gas emissions are polluting our atmosphere and
    causing significant and harmful effects on the human
    environment. Endangerment and Cause or Contribute Findings
    for Greenhouse Gases Under Section 202(a) of the Clean Air
    Act (2009 Endangerment Finding), 
    74 Fed. Reg. 66,496
    ,
    66,497–66,499 (Dec. 15, 2009). And both Republican and
    Democratic administrations have agreed: Power plants
    burning fossil fuels like coal “are far and away” the largest
    stationary source of greenhouse gases and, indeed, their role in
    greenhouse gas emissions “dwarf[s] other categories[.]” EPA
    Br. 169; see also Standards of Performance for Greenhouse
    Gas Emissions from New, Modified, and Reconstructed
    Stationary Sources: Electric Utility Generating Units (New
    Source Rule), 
    80 Fed. Reg. 64,510
    , 64,522 (Oct. 23, 2015)
    (fossil-fuel-fired power plants are “by far the largest emitters”
    of greenhouse gases).
    The question in this case is whether the Environmental
    Protection Agency (EPA) acted lawfully in adopting the 2019
    Affordable Clean Energy Rule (ACE Rule), 
    84 Fed. Reg. 32,520
     (July 8, 2019), as a means of regulating power plants’
    emissions of greenhouse gases. It did not. Although the EPA
    has the legal authority to adopt rules regulating those
    emissions, the central operative terms of the ACE Rule and the
    repeal of its predecessor rule, the Clean Power Plan, 
    80 Fed. Reg. 64,662
     (Oct. 23, 2015), hinged on a fundamental
    misconstruction of Section 7411(d) of the Clean Air Act. In
    addition, the ACE Rule’s amendment of the regulatory
    framework to slow the process for reduction of emissions is
    arbitrary and capricious. For those reasons, the ACE Rule is
    17
    vacated, and the record is remanded to the EPA for further
    proceedings consistent with this opinion.
    I. BACKGROUND
    A. T HE C LEAN AIR ACT
    In 1963, Congress passed the Clean Air Act, 
    42 U.S.C. § 7401
     et seq., “to protect and enhance the quality of the
    Nation’s air resources so as to promote the public health and
    welfare and the productive capacity of its population[,]” 
    id.
    § 7401(b)(1). Animating the Act was Congress’ finding that
    “growth in the amount and complexity of air pollution brought
    about by urbanization, industrial development, and the
    increasing use of motor vehicles[] has resulted in mounting
    dangers to the public health and welfare[.]” Id. § 7401(a)(2).
    Section 111 of the Clean Air Act, which was added in 1970
    and codified at 
    42 U.S.C. § 7411
    , directs the EPA to regulate
    any new and existing stationary sources of air pollutants that
    “cause[], or contribute[] significantly to, air pollution” and that
    “may reasonably be anticipated to endanger public health or
    welfare.” 
    42 U.S.C. § 7411
    (b)(1)(A); see 
    id.
     § 7411(d), (f)
    (providing that the EPA Administrator “shall” regulate existing
    and new sources of air pollution). A “stationary source” is a
    source of air pollution that cannot move, such as a power plant.
    See id. § 7411(a)(3) (defining “stationary source” as “any
    building, structure, facility, or installation which emits or may
    emit any air pollutant[]”). An example of a common non-
    stationary source of air pollution is a gas-powered motor
    vehicle. See Utility Air Regulatory Group v. EPA (UARG), 
    573 U.S. 302
    , 308 (2014).
    Within 90 days of the enactment of Section 7411, the EPA
    Administrator was to promulgate a list of stationary source
    categories that “cause[], or contribute[] significantly to, air
    18
    pollution[.]” 
    42 U.S.C. § 7411
    (b)(1)(A). In 1971, the
    Administrator included fossil-fuel-fired steam-generating
    power plants on that list. Air Pollution Prevention and Control:
    List of Categories of Stationary Sources, 
    36 Fed. Reg. 5,931
    (March 31, 1971); see also New Source Rule, 80 Fed. Reg. at
    64,527–64,528. Today’s power plants fall in that same
    category. ACE Rule, 84 Fed. Reg. at 32,557 n.250.
    Once a stationary source category is listed, the
    Administrator must promulgate federal “standards of
    performance” for all newly constructed sources in the category.
    
    42 U.S.C. § 7411
    (b)(1)(B). The Act defines a “standard of
    performance” as
    a standard for emissions of air pollutants which
    reflects the degree of emission limitation achievable
    through the application of the best system of emission
    reduction which (taking into account the cost of
    achieving such reduction and any nonair quality
    health and environmental impact and energy
    requirements) the Administrator determines has been
    adequately demonstrated.
    
    Id.
     § 7411(a)(1).
    Once such a new source regulation is promulgated, the
    Administrator also must issue emission guidelines for already-
    existing stationary sources within that same source category.
    
    42 U.S.C. § 7411
    (d)(1)(A)(ii); see also American Elec. Power
    Co., Inc. v. Connecticut (AEP), 
    564 U.S. 410
    , 424 (2011).
    While the new source standards are promulgated and
    enforced entirely by the EPA, the Clean Air Act prescribes a
    process of cooperative federalism for the regulation of existing
    sources. Under that structure, the statute delineates three
    distinct regulatory steps involving three sets of actors—the
    19
    EPA, the States, and regulated industry—each of which has a
    flexible role in choosing how to comply. See 
    42 U.S.C. § 7411
    (a)(1), (d). This allows each State to work with the
    stationary sources within its jurisdiction to devise a plan for
    meeting the federally promulgated quantitative guideline for
    emissions. See 
    id.
     § 7411(d).
    The process starts with the EPA first applying its expertise
    to determine “the degree of emission limitation achievable
    through the application of the best system of emission
    reduction” that “has been adequately demonstrated.” 
    42 U.S.C. § 7411
    (a)(1); see 
    40 C.F.R. § 60
    .22a. That system must “tak[e]
    into account the cost of achieving such reduction and any
    nonair quality health and environmental impact and energy
    requirements[.]”      
    42 U.S.C. § 7411
    (a)(1).         Once the
    Administrator identifies the best system of emission reduction,
    she then determines the amount of emission reduction that
    existing sources should be able to achieve based on the
    application of that system and adopts corresponding emission
    guidelines. Id.; see also, e.g., ACE Rule, 84 Fed. Reg. at
    32,523; Clean Power Plan, 80 Fed. Reg. at 64,719.
    Each State then submits to the EPA a plan that
    (i) establishes standards of performance for that State’s
    existing stationary sources’ air pollutants (excepting pollutants
    already subject to separate federal emissions standards), and
    (ii) “provides for the implementation and enforcement of such
    standards of performance[]” by the State.             
    42 U.S.C. § 7411
    (d)(1); see 
    40 C.F.R. § 60
    .23a. The standards of
    performance must “reflect[]” the emission targets that the EPA
    has determined are achievable. 
    42 U.S.C. § 7411
    (a)(1). In this
    context, a state standard need not adopt the best system
    identified by the EPA to “reflect[]” it. Id.; see 
    40 C.F.R. § 60
    .24a(c). Instead, the Clean Air Act affords States
    significant flexibility in designing and enforcing standards that
    20
    employ other approaches so long as they meet the emission
    guidelines prescribed by the Agency.
    If a State fails to submit a satisfactory plan, the EPA may
    prescribe a plan for that State. 
    42 U.S.C. § 7411
    (d)(2)(A); see
    
    40 C.F.R. § 60
    .27a(c)-(e). Similarly, if the State submits a plan
    but fails to enforce it, the EPA itself may enforce the plan’s
    terms. 
    Id.
     § 7411(d)(2)(B).
    The third and final set of relevant actors are the regulated
    entities themselves, to which, under the Act, the States may
    afford leeway in crafting compliance measures. See Clean
    Power Plan, 80 Fed. Reg. at 64,666; ACE Rule, 84 Fed. Reg.
    at 32,555.
    The EPA has exercised its authority under Section 7411
    over the years to set emission limitations for different types of
    air pollution from various categories of existing sources. See
    
    42 Fed. Reg. 12,022
     (March 1, 1977) (fluorides from phosphate
    fertilizer plants); 
    42 Fed. Reg. 55,796
     (Oct. 18, 1977) (acid
    mist from sulfuric acid plants); 
    44 Fed. Reg. 29,828
     (May 22,
    1979) (total reduced sulfur from kraft pulp plants); 
    45 Fed. Reg. 26,294
     (April 17, 1980) (fluorides from primary
    aluminum plants); 
    60 Fed. Reg. 65,387
     (Dec. 19, 1995)
    (various pollutants from municipal waste combustors); 
    61 Fed. Reg. 9905
     (March 12, 1996) (landfill gases from municipal
    solid waste landfills); 
    70 Fed. Reg. 28,606
     (May 18, 2005)
    (mercury from coal-fired power plants).
    The Clean Air Act is a comprehensive statute that includes
    a variety of regulatory programs for tackling air pollution in
    addition to Section 7411. Regulated parties may be subject to
    one or more programs. As relevant here, the National Ambient
    Air Quality Standards (NAAQS) provisions, 
    42 U.S.C. §§ 7408
    –7410, govern the levels of specified air pollutants that
    may be present in the atmosphere to protect air quality and the
    21
    public health and welfare. The Hazardous Air Pollutants
    program, 
    id.
     § 7412, directs the EPA to establish strict emission
    limitations for the most dangerous air pollutants emitted from
    major sources. Section 7411’s cooperative federalism program
    for existing sources operates as a gap-filler, requiring the EPA
    to regulate harmful emissions not controlled under those other
    two programs. Id. § 7411(d)(1)(i).
    B. E LECTRICITY AND CLIMATE CHANGE
    1. Electricity
    Electricity powers the world. Chances are that you are
    reading this opinion on a device that consumes electricity. Yet
    two distinct characteristics of electricity make its production
    and delivery in the massive quantities demanded by consumers
    an exceptionally complex process. First, unlike most products,
    electricity is a perfectly fungible commodity. Grid Experts
    Amicus Br. 6. A watt of electricity is a watt of electricity, no
    matter who makes it, how they make it, or where it is
    purchased. Second, at least as of now, this highly demanded
    product cannot be effectively stored at scale after it is created.
    Paul L. Joskow, Creating a Smarter U.S. Electricity Grid, 26
    J. ECON. PERSP. 29, 31–33 (2012).1 Instead, electricity must
    1
    Change in storage capacity is picking up speed. See generally
    Richard L. Revesz & Burcin Unel, Managing the Future of the
    Electricity Grid: Energy Storage and Greenhouse Gas Emissions,
    42 HARV. ENV’T L. REV. 139, 140–141 (2018) (describing ongoing
    declines in cost of storage); LAZARD, LAZARD’S LEVELIZED COST
    OF STORAGE ANALYSIS—VERSION 6.0 (2020) (noting “storage costs
    have declined across most use cases and technologies, particularly
    for shorter-duration applications, in part driven by evolving
    preferences in the industry”). Nevertheless, the grid’s production
    capacity still far exceeds its present storage capacity. Univ. of Mich.
    22
    constantly be produced, and is almost instantaneously
    consumed. See Clean Power Plan, 80 Fed. Reg. at 64,677,
    64,692; Grid Experts Amicus Br. 8.
    Those unique attributes led to the creation of the American
    electrical grid. 2 The grid has been called the “supreme
    engineering achievement of the 20th century,” MASS. INST. OF
    TECH., THE FUTURE OF THE ELECTRIC GRID 1 (2011)
    (formatting modified), and it is an exceptionally complex,
    interconnected system. “[A]ny electricity that enters the grid
    immediately becomes a part of a vast pool of energy that is
    constantly moving[.]” New York v. FERC, 
    535 U.S. 1
    , 7
    (2002). That means that units of electricity as delivered to the
    user are identical, no matter their source. On the grid, there is
    no coal-generated electricity or renewable-generated
    electricity; there is just electricity. See Clean Power Plan, 80
    Fed. Reg. at 64,692; Grid Experts Amicus Br. 7–8. Also,
    because storing electricity for any length of time remains
    technically challenging and often costly, the components of the
    grid must operate as a perfectly calibrated machine to deliver
    the amount of electricity that all consumers across the United
    States need at the moment they need it. Grid Experts Amicus
    Ctr. for Sustainable Sys., U.S. GRID ENERGY STORAGE (Sept. 2020),
    http://css.umich.edu/sites/default/files/US%20Grid%20Energy%20
    Storage_CSS15-17_e2020.pdf (last visited Jan. 11, 2021) (United
    States has 1,100 gigawatts of installed generation capacity and just
    23 gigawatts of storage capacity).
    2
    Technically, “grids.” There are three regional grids in the
    contiguous United States: Eastern, Western, and Texas. Grid
    Experts Amicus Br. 9; see also United States Dep’t of Energy, North
    American Electric Reliability Corporation Interconnections,
    https://www.energy.gov/oe/downloads/north-american-electric-
    reliability-corporation-interconnections (last visited Jan. 11, 2021).
    23
    Br. 8, 10–11; see also 80 Fed. Reg. at 64,677. “If [someone]
    in Atlanta on the Georgia [leg of the] system turns on a light,
    every generator on Florida’s system almost instantly is caused
    to produce some quantity of additional electric energy which
    serves to maintain the balance in the interconnected system[.]”
    Federal Power Comm’n v. Florida Power & Light Co., 
    404 U.S. 453
    , 460 (1972) (citation omitted). “Like orchestra
    conductors signaling entrances and cut-offs, grid operators use
    automated systems to signal particular generators to dispatch
    more or less power to the grid as needed over the course of the
    day, thus ensuring that power pooled on the grid rises and falls
    to meet changing demand.” Grid Experts Amicus Br. 11.
    Most generators of electricity on the American grid create
    power by burning fossil fuels like coal, oil, and natural gas. See
    United States Energy Information Administration (EIA),
    Frequently Asked Questions: What Is U.S. Electricity
    Generation by Energy Source? (Nov. 2, 2020),
    https://www.eia.gov/tools/faqs/faq.php?id=427&t=3             (last
    visited Jan. 11, 2021) (fossil fuels represented 62.6 percent of
    electricity generation in 2019). Some of those power plants
    take a fossil fuel (usually coal) and burn it in a water boiler to
    make steam. Other power plants take a different fossil fuel
    (usually natural gas), mix it with highly compressed air, and
    ignite it to release a combination of super-hot gases. Either
    way, that steam or superheated mixture is piped into giant
    turbines that catch the gases and rotate at extreme speeds.
    Those turbines turn generators, which spin magnets within wire
    coils to produce electricity. EIA, Electricity Explained
    (Nov. 9, 2020), https://www.eia.gov/energyexplained/
    electricity/how-electricity-is-generated.php (last visited Jan
    11, 2021).
    24
    2. Climate Change and the Federal Government
    Electrical power has become virtually as indispensable to
    modern life as air itself. But electricity generation has come
    into conflict with air quality in ways that threaten human health
    and well-being when power generated by burning fossil fuels
    emits carbon dioxide and other polluting greenhouse gases into
    the air.
    Since the late 1970s, the federal government has focused
    “serious attention” on the effects of carbon dioxide pollution
    on the climate. Massachusetts v. EPA, 
    549 U.S. at 507
    . In
    1978, Congress adopted the National Climate Program Act,
    Pub. L. No. 95-367, 
    92 Stat. 601
    , which directed the President
    to study and devise an appropriate response to “man-induced
    climate processes and their implications[,]” 
    id.
     § 3; see
    Massachusetts v. EPA, 
    549 U.S. at
    507–508. In response, the
    National Academy of Sciences’ National Research Council
    reported “no reason to doubt that climate changes will result”
    if “carbon dioxide continues to increase,” and “[a] wait-and-
    see policy may mean waiting until it is too late.”
    Massachusetts v. EPA, 
    549 U.S. at 508
     (quoting CLIMATE
    RESEARCH BOARD , CARBON D IOXIDE & CLIMATE:
    A SCIENTIFIC ASSESSMENT, at viii (1979)).
    In 1987, Congress passed the Global Climate Protection
    Act, which found that “manmade pollution[,]” including “the
    release of carbon dioxide, * * * may be producing a long-term
    and substantial increase in the average temperature on Earth[.]”
    Pub. L. No. 100-204, Title XI, §1102(1), 
    101 Stat. 1407
    , 1408
    (codified at 
    15 U.S.C. § 2901
     note). The Climate Protection
    Act directed the EPA to formulate a “coordinated national
    policy on global climate change.” 
    Id.
     § 1103(b), 101 Stat. at
    1408; see Massachusetts v. EPA, 
    549 U.S. at 508
    .
    25
    It was not until the Supreme Court’s 2007 decision in
    Massachusetts v. EPA, however, that the Court confirmed that
    carbon dioxide and other greenhouse gas emissions constituted
    “air pollutant[s]” covered by the Clean Air Act. See 
    549 U.S. at 528
    . The Supreme Court explained that the Clean Air Act’s
    “sweeping definition of ‘air pollutant’ includes ‘any air
    pollution agent or combination of such agents, including any
    physical, chemical . . . substance or matter which is emitted
    into or otherwise enters the ambient air[.]’” 
    Id.
     at 528–529
    (quoting 
    42 U.S.C. § 7602
    (g)). The Act, the Supreme Court
    held, “is unambiguous” in that regard. 
    Id. at 529
    . “On its face,
    the definition embraces all airborne compounds of whatever
    stripe, and underscores that intent through the repeated use of
    the word ‘any.’” 
    Id.
     And “[c]arbon dioxide” and other
    common greenhouse gases are “without a doubt” chemical
    substances that are “emitted into . . . the ambient air.” 
    Id.
    (quoting 
    42 U.S.C. § 7602
    (g)).
    Given that statutory command, the Supreme Court ruled
    that the EPA “can avoid taking further action” to regulate such
    pollution “only if it determines that greenhouse gases do not
    contribute to climate change” or offers some reasonable
    explanation for not resolving that question. Massachusetts v.
    EPA, 
    549 U.S. at 533
    .
    Taking up the mantle, the EPA in 2009 found
    “compelling[]” evidence that emissions of greenhouse gases
    are polluting the atmosphere and are endangering human health
    and welfare by causing significant damage to the environment.
    2009 Endangerment Finding, 74 Fed. Reg. at 66,497; see id.
    (“[T]he Administrator finds that greenhouse gases in the
    atmosphere may reasonably be anticipated both to endanger
    public health and to endanger public welfare. * * * The
    Administrator has determined that the body of scientific
    evidence compellingly supports this finding.”); id. at 66,497–
    26
    66,499. The EPA concluded that “‘compelling’ evidence
    supported the ‘attribution of observed climate change to
    anthropogenic’ [that is, human-influenced] emissions of
    greenhouse gases[.]” AEP, 
    564 U.S. at 417
     (quoting 74 Fed.
    Reg. at 66,518). The “[c]onsequent dangers of greenhouse gas
    emissions,” the EPA determined, include
    increases in heat-related deaths; coastal inundation
    and erosion caused by melting icecaps and rising sea
    levels; more frequent and intense hurricanes, floods,
    and other “extreme weather events” that cause death
    and destroy infrastructure; drought due to reductions
    in mountain snowpack and shifting precipitation
    patterns; destruction of ecosystems supporting
    animals and plants; and potentially “significant
    disruptions” of food production.
    Id. (quoting 74 Fed. Reg. at 66,524–66,535).
    Not long thereafter, the Supreme Court ruled that the
    significant greenhouse gas pollution caused by fossil-fuel-fired
    power plants is subject to regulation under Section 7411 of the
    Clean Air Act. AEP, 
    564 U.S. at 424
     (holding that Section
    7411 “speaks directly to emissions of carbon dioxide from
    [fossil-fuel-fired] plants[]”) (internal quotation marks omitted).
    The Court concluded that the EPA’s expertise made it “best
    suited to serve as primary regulator of greenhouse gas
    emissions.” 
    Id. at 428
    .
    In 2015, with the 2009 carbon dioxide endangerment
    finding continuing in effect, the EPA reaffirmed that
    greenhouse gases “endanger public health, now and in the
    future.” New Source Rule, 80 Fed. Reg. at 64,518. The EPA
    explained that, “[b]y raising average temperatures, climate
    change increases the likelihood of heat waves, which are
    associated with increased deaths and illnesses[,]” particularly
    27
    among “[c]hildren, the elderly, and the poor[.]” Id. at 64,517.
    In addition, the EPA found that “[c]limate change impacts
    touch nearly every aspect of public welfare.” Id. Among the
    “multiple threats caused by human emissions of [greenhouse
    gases],” the EPA pointed to climate changes that “are expected
    to place large areas of the country at serious risk of reduced
    water supplies, increased water pollution, and increased
    occurrence of extreme events such as floods and droughts.” Id.
    The EPA “emphasize[d] the urgency of reducing [greenhouse
    gas] emissions due to * * * projections that show [greenhouse
    gas] concentrations climbing to ever-increasing levels in the
    absence of mitigation[,]” citing independent assessments
    finding that, “without a reduction in emissions, CO2
    concentrations by the end of the century would increase to
    levels that the Earth has not experienced for more than 30
    million years.” Id. at 64,518.
    The federal government’s consistent recognition of the
    danger to public health and welfare caused by climate change,
    and the signal contribution of greenhouse gas emissions from
    power plants to global warming, continues to the present. In
    2018, President Trump’s administration concluded that
    “Earth’s climate is now changing faster than at any point in the
    history of modern civilization, primarily as a result of human
    activities.” U.S. GLOBAL CHANGE RESEARCH PROGRAM,
    FOURTH NATIONAL CLIMATE A SSESSMENT, VOLUME II:
    IMPACTS, RISKS, AND ADAPTATION IN THE UNITED STATES
    (REPORT- IN-B RIEF) 24 (2018). The administration added that
    “the evidence of human-caused climate change is
    overwhelming and continues to strengthen,” and “the impacts
    of climate change are intensifying across the country[.]” Id. at
    26 (emphasis omitted). “Climate-related changes in weather
    patterns and associated changes in air, water, food, and the
    environment are affecting the health and well-being of the
    American people, causing injuries, illnesses, and death.” Id. at
    28
    102. The administration’s report concluded that urgent action
    is needed to mitigate these dangers because “[f]uture risks from
    climate change depend primarily on decisions made today.” Id.
    at 13.
    In preparing the ACE Rule, the EPA expressly
    acknowledged its continued adherence to the 2015
    endangerment finding. 84 Fed. Reg. at 32,533 (The 2015 New
    Source Rule “continues to provide the requisite predicate for
    applicability of [Clean Air Act] section 111(d).”); id. at 32,557
    n.250; see also Emission Guidelines for Greenhouse Gas
    Emissions from Existing Electric Utility Generating Units;
    Revisions to Emission Guideline Implementing Regulations;
    Revisions to New Source Review Program: Proposed Rule, 
    83 Fed. Reg. 44,746
    , 44,751 (Aug. 31, 2018) (confirming that the
    2015 New Source Rule “remains on the books[]”); EPA
    Br. 217.
    That endangerment finding provided the essential factual
    foundation—and triggered a statutory mandate—for the EPA
    to regulate greenhouse gas emissions from both new and
    existing power plants. See New Source Rule, 80 Fed. Reg. at
    64,527, 64,529–64,532; Clean Power Plan, 80 Fed. Reg. at
    64,683–64,690; see also 
    42 U.S.C. §§ 7411
    (b)(1)(A)–(B) (duty
    to regulate new stationary sources that contribute significantly
    to dangerous pollution identified in endangerment finding),
    7411(d)(1)(A)(ii) (duty to regulate existing stationary sources
    that would be regulated under § 7411(b) if they were new
    stationary sources). Recall, Section 7411(b)(1)(A) provides
    that the EPA Administrator “shall” regulate any category of
    sources that, “in his judgment * * * causes, or contributes
    significantly to, air pollution which may reasonably be
    anticipated to endanger public health or welfare.” The EPA
    endangerment findings reflect such well-established risks.
    29
    C. T HE C LEAN POWER PLAN
    In the last decade, the EPA has heavily focused its
    regulation of greenhouse gases on the power sector because
    “power plants are far and away the largest stationary-category
    source of greenhouse gases[,]” and “power plants’
    contributions to CO2 pollution * * * dwarf[] other
    categories[.]” EPA Br. 169.
    In October 2015, the EPA issued greenhouse gas emission
    standards for new and modified power plants. See New Source
    Rule, 80 Fed. Reg. at 64,510. In so doing, the EPA found that,
    “[a]ll told, these fossil fuel-fired [power plants] emit almost
    one-third of all U.S. [greenhouse gas] emissions, and are
    responsible for almost three times as much as the emissions
    from the next ten stationary source categories combined.” Id.
    at 64,531. That rule and finding remain in effect and are not
    challenged in this litigation.
    The EPA then turned to the regulation of existing power
    plants. The EPA began, as the Clean Air Act requires, by
    determining the best system of emission reduction that has
    been adequately demonstrated for existing fossil-fuel-fired
    power plants. See 
    42 U.S.C. § 7411
    (a)(1); Clean Power Plan,
    80 Fed. Reg. at 64,718. In identifying that system, the EPA
    chose to build on the established grid system and methods of
    operation already adopted by and familiar to the power sector.
    See 80 Fed. Reg. at 64,725, 64,727–64,728. The regulations
    and standards that the EPA formulated came to be known as
    the Clean Power Plan. Id. at 64,663.
    In the Clean Power Plan, the EPA determined that a
    combination of three existing methods of emission reduction—
    which the Plan referred to as building blocks, 80 Fed. Reg. at
    64,667—formed the “best system of emission reduction,” 
    42 U.S.C. § 7411
    (a)(1).
    30
    First, the system incorporated heat-rate improvements—
    that is, technological measures that improve efficiency at coal-
    fired steam power plants and, in that way, reduce the amount
    of coal that must be burned to produce each watt of electricity
    to the grid. 80 Fed. Reg. at 64,667.
    Second, the system added the “substitut[ion of] increased
    generation from lower-emitting existing natural gas combined
    cycle units for generation from higher-emitting affected steam
    generating” power plants, which are mostly coal-fired. 80 Fed.
    Reg. at 64,667.
    Third, the system prioritized the use of electricity
    generated from zero-emitting renewable-energy sources over
    electricity from the heavily greenhouse-gas-polluting fossil-
    fuel-fired power plants. 80 Fed. Reg. at 64,667.
    Those second and third methods of emission control are
    often referred to as “generation shifting” because the
    reductions occur when the source of power generation shifts
    from higher-emission power plants to less-polluting sources of
    energy. See Clean Power Plan, 80 Fed. Reg. at 64,728–64,729.
    As the EPA observed, such shifts in generation already occur
    all the time as a matter of grid mechanics. That is, within the
    grid’s “Constrained Least-Cost Dispatch” system, production
    from “generators with the lowest variable costs” will be
    dispatched “first, as system operational limits allow, until all
    demand is satisfied.”        Grid Experts Amicus Br. 12.
    “[R]enewable energy generators typically receive dispatch
    priority because they have lower variable costs than fossil-fuel-
    fired generators, which must purchase fuel.” Id. at 13 (citing
    80 Fed. Reg. at 64,693). The EPA found that most electricity
    is generated by diversified utilities that could achieve most or
    all of the shift to lower- or no-emission generation by
    31
    reassessing the dispatch priority of their own assets. See 80
    Fed. Reg. at 64,796, 64,804.
    As required by Section 7411(a)(1), the EPA then
    quantified the degree of emission reduction achievable under
    that three-tier best system for the relevant fossil-fuel-fired
    power plants and translated it into state-specific emissions
    goals for 2030. Clean Power Plan, 80 Fed. Reg. at 64,824–
    64,825. To permit additional flexibility, the Plan actually
    provided two alternative types of targets: rate-based goals,
    reflecting the rate of emission per certain amount of generation,
    and mass-based goals, reflecting the total emission from a
    State’s sources. Id. at 64,820, 64,824–64,825 Tables 12, 13.
    The alternative metrics were an added source of flexibility for
    States in choosing how they would meet the federal limits.
    Under the Clean Air Act, States could then propose plans
    that set standards of performance for their existing power
    plants that would meet those emission goals. Clean Power
    Plan, 80 Fed. Reg. at 64,664. In doing so, the States and their
    power plants were under no obligation to use the three specific
    methods that the EPA had identified in determining the best
    system of emission reduction. Rather, consistent with Section
    7411(d)’s cooperative federalism approach, States were free to
    choose any measures, approaches, or technologies that they
    deemed appropriate to meet the federal guidelines. For
    example, they could adopt technological controls already in use
    by some power plants like carbon capture and sequestration (by
    which carbon dioxide is captured from the plant’s flue gas
    before it is emitted and then securely stored so it cannot reach
    the atmosphere) or co-firing (where fuels that release less
    carbon dioxide are burned alongside fuels that release more to
    reduce the amount of the latter used). See id. at 64,883. The
    EPA also suggested that States might rely on emissions-trading
    32
    programs (often referred to as cap-and-trade) and other
    potential compliance strategies. Id. at 64,887.
    The EPA found that its proposed approach was “consistent
    with, and in some ways mirrors, the interconnected,
    interdependent and highly regulated nature of the utility power
    sector[]” and its grid, as well as “the daily operation of affected
    [power plants] within this framework, and the critical role of
    utilities in providing reliable, affordable electricity at all times
    and in all places within this complex, regulated system.” Clean
    Power Plan, 80 Fed. Reg. at 64,678.
    The Clean Power Plan was challenged in this court. West
    Virginia v. EPA, No. 15-1363 (and consolidated cases) (D.C.
    Cir. Oct. 23, 2015). After we heard argument en banc, but
    before we issued a decision, that litigation was held in
    abeyance and ultimately dismissed as the EPA reassessed its
    position. No. 15-1363, Docs. 1673071, 1806952.
    D. T HE ACE RULE
    In 2019, the EPA issued a new rule that repealed and
    replaced the Clean Power Plan: The Affordable Clean Energy
    (ACE) Rule. See Repeal of the Clean Power Plan; Emission
    Guidelines for Greenhouse Gas Emissions from Existing
    Electric Utility Generating Units; Revisions to Emission
    Guidelines Implementing Regulations, 
    84 Fed. Reg. 32,520
    (July 8, 2019). That Rule is the subject of this litigation.
    1. Repeal of the Clean Power Plan
    At the outset, the ACE Rule repealed the Clean Power
    Plan. The EPA explained that it felt itself statutorily compelled
    to do so because, in its view, “the plain meaning” of Section
    7411(d) “unambiguously” limits the best system of emission
    reduction to only those measures “that can be put into operation
    33
    at a building, structure, facility, or installation.” ACE Rule, 84
    Fed. Reg. at 32,523–32,524. Because the Clean Power Plan’s
    best system was determined by using some emission control
    measures that the EPA characterized as physically operating
    off the site of coal-fired power plants—such as some forms of
    generation shifting and emissions trading—the EPA concluded
    that it had no choice but to repeal the Plan. Id. The EPA
    emphasized “that [its] action is based on the only permissible
    reading of the statute and [it] would reach that conclusion even
    without consideration of the major question doctrine,” while
    adding that application of that latter doctrine “confirms the
    unambiguously expressed intent” of Section 7411. Id. at
    32,529.
    2. Best System of Emission Reduction
    Considering its authority under Section 7411 to be
    confined to physical changes to the power plants themselves,
    the EPA’s ACE Rule determined a new best system of emission
    reduction for coal-fired power plants only. The EPA left
    unaddressed in this rulemaking (or elsewhere) greenhouse gas
    emissions from other types of fossil-fuel-fired power plants,
    such as those fired by natural gas or oil. ACE Rule, 84 Fed.
    Reg. at 32,533.
    The EPA’s proposed system relied solely on heat-rate
    improvement technologies and practices that could be applied
    at and to existing coal-fired power plants. ACE Rule, 84 Fed.
    Reg. at 32,525, 32,537. The EPA selected only seven heat-rate
    improvement techniques as components of its best system. Id.
    at 32,537. Six of those measures were new-to-the-plant
    technologies or “equipment upgrades.” Id. at 32,536–32,537
    (naming as part of the best system (1) adding or upgrading
    neural networks and intelligent sootblowers; (2) upgrading
    boiler feed pumps; (3) replacing or upgrading air heater and
    34
    duct leakage control devices; (4) adding variable frequency
    drives in feed pumps and induced-draft fans; (5) blade path
    upgrades; and (6) redesigning or replacing economizers). The
    seventh measure was the use of “best operating and
    maintenance practices” implementing heat-rate improvement
    techniques. Id. at 32,537, 32,540. The EPA limited itself to
    techniques that could be “applied broadly” to the Nation’s coal-
    fired plants, which primarily amounted to upgrades to existing
    equipment. Id. at 32,536.
    The EPA explained that only five of the seven listed
    techniques directly reduce the heat rate of power plants. See
    ACE Rule, 84 Fed. Reg. at 32,538–32,540. The other two
    techniques—replacing or upgrading the boiler feed pump and
    installing variable frequency drives—serve to reduce the
    amount of energy that a power plant must use to run its own
    general operations. Id. at 32,538–32,539.3 So those two
    techniques do not make a power plant more efficient in turning
    coal into power, but instead allow power plants to dispatch
    more of the power they produce to the grid rather than using it
    internally. Id.
    3
    The boiler feed pump is a device that is used to pump water
    into the boiler. 84 Fed. Reg. at 32,538. It consumes a “large
    fraction” of the power used to run the plant. Id. Because the boiler
    feed pump requires so much energy, the EPA suggested that
    “maintenance on these pumps should be rigorous to ensure both
    reliability and high-efficiency operation.” Id. Variable frequency
    drives “enable[] very precise and accurate speed control” of both
    boiler feed pumps and “induced draft (ID) fans,” which “maintain
    proper flue gas flow through downstream air pollutant control
    equipment[.]” Id. at 32,539. This precise control would reduce the
    excess use of fans and pumps, requiring less energy. See id.
    35
    The EPA identified two of its other chosen techniques—
    blade path and economizer upgrades—as the measures that, of
    all the considered technologies, were “expected to offer some
    of the largest [heat-rate] improvements.” ACE Rule, 84 Fed.
    Reg. at 32,537 (showing table predicting highest heat-rate
    improvement range in economizer redesign or replacements
    and blade path upgrades).4
    But the EPA then stated that it expected some power plants
    would not adopt those two technologies because their use could
    trigger additional regulation that the companies would find
    burdensome. 84 Fed. Reg. at 32,537 (“[B]ased on public
    comments * * *, [blade path upgrades and economizer redesign
    or replacement] are [heat-rate improvement] technologies that
    have the most potential to trigger [New Source Review]
    requirements.”). In fact, the EPA did not model those two
    techniques in its regulatory impact analysis precisely because
    it was unlikely that they would be adopted. J.A. 1656–1657.
    Finally, the EPA acknowledged that the proposed
    technologies could create a “rebound effect.” ACE Rule, 84
    Fed. Reg. at 32,542. A rebound effect means that net carbon
    dioxide emissions actually increase as a result of the efficiency
    improvements made by power plants. Id. This happens
    because, as the efficiency upgrades make coal-based energy
    cheaper to produce, coal-fired power plants will have an
    incentive to run more often, thereby increasing their overall
    emissions. Id. The EPA found that risk of increased emissions
    irrelevant because its best system of emission reduction “is
    aimed at improving a source’s emissions rate performance at
    4
    “Blade path upgrades” consist of upgrades to the steam
    turbine. Economizers are heat-exchange devices that “capture waste
    heat from boiler flue gas” and use that captured heat to help heat the
    boiler feedwater. Id. at 32,540.
    36
    the unit-level,” rather than reducing the overall volume of
    emissions by individual sources. Id. at 32,543.
    In choosing its seven proposed power-plant-based heat-
    rate improvement technologies, the EPA excluded from its best
    system several other suggested methods of reducing emissions,
    including (1) natural gas co-firing, repowering, and refueling;
    (2) biomass co-firing; and (3) carbon capture and storage
    technologies. ACE Rule, 84 Fed. Reg. at 32,543–32,547. The
    EPA rejected biomass co-firing primarily because “any
    potential net reductions in emissions from biomass use occur
    outside of the regulated source,” and so do not fall within the
    EPA’s reading of Section 7411(d) as confined to emission
    limits imposed at and to individual plants. Id. at 32,546. The
    EPA excluded natural gas co-firing and carbon capture and
    storage from its own best system, citing cost, geographical, and
    operational concerns. Id. at 32,544–32,545, 32,547–32,548.
    The EPA provided that sources could choose to use natural gas
    co-firing or carbon capture—but not biomass co-firing—to
    meet state-established standards of performance. Id. at 32,555.
    3. Degree of Emission Limitation Achievable
    Having determined its best system of emission reduction,
    the EPA then purported to prescribe the “degree of emission
    limitation achievable,” which States could use to create their
    own standards of performance. 
    42 U.S.C. § 7411
    (a)(1). What
    the EPA produced as its emission guidelines was a chart that
    prescribed heat-rate improvement “ranges” for each of the
    EPA’s chosen heat-rate improvement technologies, organized
    by power plants of differing sizes. ACE Rule, 84 Fed. Reg. at
    32,537. The ranges show how much heat-rate improvement
    can be “expected” from use of each of the identified
    technologies. Id.
    37
    The EPA was explicit, though, that the “potential” range
    of heat-rate reduction was only illustrative and that the actual
    reduction for each of the EPA’s chosen technologies would be
    “unit-specific” and would “depend upon a range of unit-
    specific factors.” ACE Rule, 84 Fed. Reg. at 32,537–32,538.
    In that way, the ACE Rule made States responsible for
    evaluating “[heat-rate improvement] potential, technical
    feasibility, and applicability for each of the [best system of
    emission reduction] candidate technologies” on a power-plant–
    by–power-plant basis. Id. at 32,538. The ACE Rule expressly
    left States free to establish their own standards of performance
    for their power plants that “reflect a value of [heat-rate
    improvement] that falls outside” the ranges provided in the
    EPA’s chart. Id. (emphasis added). In other words, the
    minimums listed in the EPA’s emission-reduction chart were
    only suggestions.
    The EPA explained that its non-mandatory ranges of
    efficiency reduction were valid because the applicability of the
    heat-rate improvement techniques to different plants and the
    effectiveness of each power plant’s existing technology may
    vary. See ACE Rule, 84 Fed. Reg. at 32,538 (stating that “not
    all” of the technologies would be “applicable or warranted at
    the level of a particular facility due to source-specific factors
    such as the site-specific operational and maintenance history,
    the design and configuration, [or] the expected operating
    plans”).
    The EPA predicted that its ACE Rule would reduce carbon
    dioxide emissions by less than 1% from baseline emission
    projections by 2035. J.A. 1651. That calculation did not
    reflect emission increases that could result from the rebound
    effect.
    38
    4. Implementing Regulations
    The ACE Rule included some new regulations under
    Section 7411(d). ACE Rule, 84 Fed. Reg. at 32,575-32,584
    (codified at 40 C.F.R. pt. 60, subpart Ba). As relevant here, the
    regulations significantly extend the States’ deadlines for the
    development and submittal of their plans for emission
    reduction from nine months to three years. See 
    40 C.F.R. § 60
    .23a(a)(1). Similarly, the new regulations extend the
    EPA’s deadline to act on those plans from four months to one
    year. 
    40 C.F.R. § 60
    .27a(b). The new regulations also extend
    the EPA’s deadline to substitute its own plan for a non-
    compliant State’s plan from six months after the submission
    deadline to two years after a finding that the plan was
    incomplete, disapproved, or unsubmitted. See 
    40 C.F.R. § 60
    .27a(c). Finally, the requirement that States demonstrate
    compliance progress is now triggered only where a State’s
    compliance schedule stretches more than two years from when
    its plan was originally due, as opposed to the one-year period
    in the prior regulations. See 
    40 C.F.R. § 60
    .24a(d).
    E. PETITIONS FOR REVIEW
    Twelve petitions for review of the ACE Rule were timely
    filed in this court and consolidated in this case. Nos. 19‑1140
    (lead case), 19‑1165, 19‑1166, 19‑1173, 19‑1175, 19‑1176,
    19‑1177, 19‑1179, 19‑1185, 19‑1186, 19‑1187, 19‑1188. The
    petitioners fall into three groups.
    The first grouping consists of petitioners who seek review
    of the ACE Rule’s conclusion that Section 7411 only permits
    emission reduction measures that can be implemented at and
    applied to the source. Those petitioners include (i) a coalition
    of State and municipal governments; (ii) power utilities;
    39
    (iii) trade associations from the renewable energy industry; and
    (iv) several public health and environmental advocacy groups.5
    The second grouping is petitioners who challenge the ACE
    Rule’s imposition of any emission limits as unlawful because,
    in their view, (i) the EPA failed to make a specific
    endangerment finding for carbon dioxide emitted from existing
    power plants; (ii) the EPA’s regulation of mercury emissions
    from coal-fired power plants under Section 7412 precludes the
    regulation of greenhouse gas emissions under Section 7411;
    and (iii) the EPA should have regulated carbon dioxide from
    stationary sources, including power plants, under the NAAQS
    program, 
    42 U.S.C. §§ 7408
    –7410.
    The third petitioner group is the Biogenic CO2 Coalition.
    They object only to the ACE Rule’s determination that States
    may not count biomass co-firing as a method of complying
    with numerical emission limits.
    F. JURISDICTION AND STANDARD OF REVIEW
    This court has jurisdiction to review these petitions under
    the Clean Air Act. 
    42 U.S.C. § 7607
    (b)(1); see also Sierra
    Club v. EPA, 
    955 F.3d 56
    , 61 (D.C. Cir. 2020).
    We may set aside the ACE Rule if it is “arbitrary,
    capricious, an abuse of discretion, or otherwise not in
    accordance with law.” 
    42 U.S.C. § 7607
    (d)(1)(C),
    (d)(9)(A); see also Maryland v. EPA, 
    958 F.3d 1185
    , 1196
    (D.C. Cir. 2020) (“[W]e apply the same standard of review
    under the Clean Air Act as we do under the Administrative
    5
    The public health and environmental advocacy groups also
    challenge the third prong of the ACE Rule—the new implementing
    regulations—as arbitrary and capricious.
    40
    Procedure Act.”) (quoting Allied Local & Reg’l Mfrs. Caucus
    v. EPA, 
    215 F.3d 61
    , 68 (D.C. Cir. 2000)).
    II. SECTION 7411
    A. STATUTORY CONTEXT
    In enacting the Clean Air Act, “Congress delegated to EPA
    the decision whether and how to regulate carbon-dioxide
    emissions from powerplants.” American Elec. Power Co. v.
    Connecticut (AEP), 
    564 U.S. 410
    , 426 (2011). As the Supreme
    Court has observed, 
    42 U.S.C. § 7411
     “speaks directly to” and
    outlines the framework for that regulation. 
    Id. at 424
     (internal
    quotation marks omitted). Specifically, Section 7411 marks
    out a pair of distinct regulatory tracks for stationary sources of
    air pollutants. See 
    42 U.S.C. § 7411
    (a)(2), (6). The first track
    applies to new sources, 
    id.
     § 7411(b), and the second to existing
    sources, id. § 7411(d). The statute calls for federal-state
    cooperation in regulating existing sources, affording distinct
    roles to the federal and state agencies in arriving at what
    Section 7411 calls “standards of performance” for the emission
    of air pollutants. Id. § 7411(a)(1), (c), (d)(1).
    The regulatory regimes for new and existing sources differ
    in the process by which such standards are established—and
    the roles played by the respective regulatory actors. The Act
    assigns the EPA the main regulatory role in specifying the new-
    source pollution controls: After the EPA determines that a
    particular “category of sources * * * causes, or contributes
    significantly to, air pollution which may reasonably be
    anticipated to endanger public health or welfare,” it publishes
    regulations establishing standards of performance for new
    sources in that category. Id. § 7411(b)(1).
    The process for regulating existing sources—which raise
    distinct concerns about sunk costs and the health and
    41
    environmental effects of older processes—involves more
    actors and steps. Regulation of a given category of existing
    sources is triggered by the same EPA air-pollution
    determination as for new sources. But for existing sources the
    Act adopts a cooperative-federalism approach that leaves the
    States discretion in determining how their State and industry
    can best meet quantitative emissions guidelines established by
    the EPA. See AEP, 
    564 U.S. at 424
    . Under Section 7411(d),
    the EPA and the States thus have distinct but complementary
    roles subject to different procedures and limitations. See 
    42 U.S.C. § 7411
     (a)(1), (d)(1). This case concerns the mechanics
    of that cooperative framework for existing sources and,
    specifically, restrictions the Agency now claims the statute
    imposes on regulation of the air pollutants those sources emit.
    Two provisions of Section 7411 shape the existing-source
    framework.       Subsection (a)(1) defines a standard of
    performance, by reference to the “degree of emission
    limitation” that the EPA determines is “achievable,” as:
    a standard for emissions of air pollutants which
    reflects the degree of emission limitation achievable
    through the application of the best system of emission
    reduction which (taking into account the cost of
    achieving such reduction and any nonair quality
    health and environmental impact and energy
    requirements) the Administrator determines has been
    adequately demonstrated.
    
    42 U.S.C. § 7411
    (a)(1).
    Subsection (d)(1), in turn, requires the Secretary to set up
    a system by which willing States can submit to the EPA “a plan
    which [] establishes standards of performance for any existing
    source.” 
    Id.
     § 7411(d)(1). Only “where [a] State fails to submit
    a satisfactory plan” may the EPA step in and directly
    42
    promulgate standards of performance for existing sources. Id.
    § 7411(d)(2).
    Putting these two provisions together results in what are
    best understood as three distinct steps involving three sets of
    actors, each exercising a degree of leeway in choice of control
    measures. See ACE Rule, 84 Fed. Reg. at 32,533, 32,549–
    32,550; Clean Power Plan, 80 Fed. Reg. at 64,665–64,666.
    First, under subsection (a)(1), the EPA determines the
    “best system of emission reduction” that is “adequately
    demonstrated,” taking into consideration certain enumerated
    statutory criteria: cost, any nonair quality health and
    environmental impacts, and energy requirements. 
    42 U.S.C. § 7411
    (a)(1). The Agency then issues emission guidelines that
    quantify the “degree of emission limitation achievable through
    the application of the best system” it has identified. Id.; 
    40 C.F.R. § 60
    .22a; see AEP, 
    564 U.S. at 424
    ; EPA Br. 21–22;
    ACE Rule, 84 Fed. Reg. at 32,523, 32,551.
    Second, under subsection (d)(1), States issue standards of
    performance for existing sources that comply with the EPA’s
    emission guidelines and “reflect” the achievable degree of
    emission limitation set in those guidelines. AEP, 
    564 U.S. at 424
    ; 
    42 U.S.C. § 7411
    (d)(1); 
    40 C.F.R. § 60
    .23a; see also
    Clean Power Plan, 80 Fed. Reg. at 64,666. That the standards
    must “reflect” the emission guidelines does not mean that they
    must embody the methods EPA contemplated in identifying the
    best system; rather, the States have flexibility in determining
    the specifics of the standards they issue so long as they
    accomplish the “degree of emission limitation” the EPA
    calculated based on its “best system.”
    Third, the operators of regulated stationary sources
    implement measures to ensure they will in practice comply
    with the standards of performance their state agency has
    43
    established for them. See ACE Rule, 84 Fed. Reg. at 32,555.
    States often grant regulated entities some discretion in how
    they meet those standards. See, e.g., N.Y. COMP. CODES R. &
    REGS. Tit. 6 § 201-6.4(f) (2013) (describing the “operational
    flexibility” afforded to Title V facility owners in New York
    State to “propose a range of operating conditions that will allow
    flexibility [for a facility] to operate under more than one
    operating scenario”).
    The issue before us arises at the first step—the EPA’s
    determination of the best system of emission reduction. In the
    Clean Power Plan, the Agency determined that the best system
    was one that both improved the heat rate at power plants and
    prioritized generation from lower-emitting plants ahead of
    high-emitting plants. Clean Power Plan, 80 Fed. Reg. at
    64,707. The EPA then calculated specific emission reductions
    achievable through application of that best system that it
    published as emission guidelines for States. Id. Had the Clean
    Power Plan gone into effect, States would then have submitted
    to the EPA plans based on the Agency’s guidelines that
    established standards of performance for sources in their
    jurisdictions, as provided for in subsection (d)(1). The Clean
    Power Plan left States flexibility in the measures they included
    in their plans, so long as they achieved a reduction in emissions
    at least as great as that achieved by EPA-established
    quantitative guidelines. See, e.g., id. at 64,665, 64,756–64,757,
    64,734–64,737, 64,832–64,837. And it further allowed States,
    at their option, to give leeway to sources to select alternate
    compliance measures to make the requisite reductions. See id.
    at 64,834–64,835.
    Based on what it now perceives to be an express and
    unambiguous textual limitation in Section 7411 that it says the
    Clean Power Plan overlooked, the EPA repealed that Plan and
    replaced it with the ACE Rule. The EPA’s new reading of the
    44
    statute requires the Agency, in modeling its “best system of
    emission reduction,” to consider only emission-reduction
    measures that “can be applied at and to a stationary source.”
    ACE Rule, 84 Fed. Reg. at 32,534; see also id. at 32,526–
    32,532.
    We address below the EPA’s arguments regarding how the
    text and structure of Section 7411 purportedly support this
    limitation. That discussion is necessarily somewhat abstract
    and technical. So, for starters, it is worth bringing the matter
    more concretely into view.
    Consider the effect the EPA’s new statutory interpretation
    had on its resulting Rule. First, because generation shifting is
    not, in the EPA’s view, a measure that can be applied “at and
    to” any one individual source, the ACE Rule limits the best
    system of emission reduction to heat-rate improvements alone.
    84 Fed. Reg. at 32,534–32,535. Then, instead of publishing
    emission guidelines quantifying emission reductions
    achievable through application of the best system, the ACE
    Rule identifies what the Agency has determined are the most
    effective heat-rate technologies available and a potential range
    of heat-rate improvements achievable through application of
    each of those technologies. Id. 32,535–32,537.
    As under the Clean Power Plan, the ACE Rule grants
    States flexibility in establishing standards of performance for
    sources pursuant to the Agency’s emission guidelines. Unlike
    the Clean Power Plan, however, the ACE Rule does not require
    that the States reach any specified minimum emission
    reduction.     Instead, States must merely “evaluate the
    applicability of each of the candidate technologies” to sources
    within their jurisdiction and report their conclusions back to the
    Agency. ACE Rule, 84 Fed. Reg. at 32,550, 32,538–32,561.
    The Rule recites that regulated entities have “broad
    45
    discretion” in meeting state-established standards, ACE Rule,
    84 Fed. Reg. at 32,555, yet at the same time the Rule deems
    impermissible any compliance measure that cannot be applied
    at and to the source, id. The ACE Rule thereby disqualifies
    compliance by, for example, burning biofuel, id. at 32,557–
    32,558, which emits recently captured carbon dioxide, in
    contrast to fossil fuels’ release of carbon dioxide stored away
    millions of years ago. See generally Center for Biological
    Diversity v. EPA, 
    722 F.3d 401
    , 405–406 (D.C. Cir. 2013).
    The question here is a relatively discrete one. We are not
    called upon to decide whether the approach of the ACE Rule is
    a permissible reading of the statute as a matter of agency
    discretion. Instead, the sole ground on which the EPA defends
    its abandonment of the Clean Power Plan in favor of the ACE
    Rule is that the text of Section 7411 is clear and unambiguous
    in constraining the EPA to use only improvements at and to
    existing sources in its best system of emission reduction.
    The EPA contends that its current interpretation is “the
    only permissible interpretation of the scope of the EPA’s
    authority.” ACE Rule, 84 Fed. Reg. at 32,535. Our task is to
    assess whether Section 7411 in fact compels the EPA’s new
    interpretation. And because “deference to an agency’s
    interpretation of a statute is not appropriate when the agency
    wrongly believes that interpretation is compelled by
    Congress,” Peter Pan Bus Lines, Inc. v. Fed. Motor Carrier
    Safety Admin., 
    471 F.3d 1350
    , 1354 (D.C. Cir. 2006) (quoting
    PDK Labs., Inc. v. DEA, 
    362 F.3d 786
    , 798 (D.C. Cir. 2004)
    (internal quotation marks omitted)), we may not defer to the
    EPA’s reading if it is but one of several permissible
    interpretations of the statutory language, see Negusie v. Holder,
    
    555 U.S. 511
    , 521 (2009). That is, the “regulation must be
    declared invalid, even though the agency might be able to adopt
    the regulation in the exercise of its discretion, if it ‘was not
    46
    based on the agency’s own judgment but rather on the
    unjustified assumption that it was Congress’ judgment that
    such a regulation is desirable” or required. Prill v. NLRB, 
    755 F.2d 941
    , 948 (D.C. Cir. 1985) (quoting FCC v. RCA
    Commc’ns, 
    346 U.S. 86
    , 96 (1953) (formatting modified));
    accord Arizona v. Thompson, 
    281 F.3d 248
    , 259 (D.C. Cir.
    2002) (quoting Prill, 
    755 F.2d at 948
    ).
    For the reasons explained below, Section 7411 does not,
    as the EPA claims, constrain the Agency to identifying a best
    system of emission reduction consisting only of controls “that
    can be applied at and to a stationary source.” ACE Rule, 84
    Fed. Reg. at 32,534. The EPA here “failed to rely on its own
    judgment and expertise, and instead based its decision on an
    erroneous view of the law.” Prill, 
    755 F.2d at 956
    . We
    accordingly must vacate and remand to the Agency “to
    interpret the statutory language anew.” Peter Pan Bus Lines,
    
    471 F.3d at 1354
    .
    1. Text
    As just noted, Section 7411 contemplates distinct roles for
    the EPA and the States in regulating existing stationary
    sources. See 
    42 U.S.C. § 7411
    (a)(1) (granting authority to the
    EPA to designate the best system and determine achievable
    degree of emissions reduction); 
    id.
     § 7411(d)(1) (outlining the
    States’ role in setting standards of performance for their
    sources). Nevertheless, the EPA now contends that language
    in Section 7411(a)(1) and (d)(1) “unambiguously limits the
    [best system of emission reduction] to those systems that can
    be put into operation at a building, structure, facility, or
    installation.” ACE Rule, 84 Fed. Reg. at 32,524 (emphasis in
    original); see id. at 32,528; EPA Br. 70.
    In the Agency’s current view, the only pollution-control
    methods the Administrator can consider in selecting the “best
    47
    system of emission reduction” within the meaning of Section
    7411(a) are add-ons or retrofits confined to the level of the
    individual fossil-fuel-fired power plant. ACE Rule, 84 Fed.
    Reg. at 32,524. That is so even though the record before the
    EPA shows that generation shifting to prioritize use of the
    cleanest sources of power is one of the most cost-effective
    means of reducing emissions that plants have already adopted
    and that have been demonstrated to work, and that generation
    shifting is capable of achieving far more emission reduction
    than controls physically confined to the source. See, e.g., Clean
    Power Plan, 80 Fed. Reg. at 64,693, 64,728–64,729; 2 J.A. 598;
    Grid Experts Amicus Br. 13–16. In other words, the EPA reads
    the statute to require the Agency to turn its back on major
    elements of the systems that the power sector is actually and
    successfully using to efficiently and cost-effectively achieve
    the greatest emission reductions. See Grid Experts Amicus Br.
    22 (observing that the ACE Rule “imposes greater abatement
    costs on industry than other approaches would to achieve the
    same effect”).
    The Clean Power Plan could not stand, the EPA now
    concludes, because its consideration of generation shifting
    exceeded the Agency’s narrow authority under Section 7411’s
    plain text. ACE Rule, 84 Fed. Reg. at 32,526–32,527. In
    promulgating the Clean Power Plan, the EPA read “system of
    emission reduction” to mean “a set of measures that work
    together to reduce emissions and that are implementable by the
    sources themselves.” Clean Power Plan, 80 Fed. Reg. at
    64,762. And it concluded that both heat-rate improvements
    and generation shifting “are components of a best system of
    emission reduction for the affected [electricity generating
    units] because they entail actions that the affected [units] may
    themselves undertake that have the effect of reducing their
    emissions.” Id. at 64,709 (internal quotation marks omitted).
    48
    All of that is wrong, the EPA has since decided. “[T]he
    Agency now recognizes that Congress ‘spoke to the precise
    question’ of the scope of [
    42 U.S.C. § 7411
    ](a)(1) and clearly
    precluded the unsupportable reading of that provision asserted
    in the [Clean Power Plan].” ACE Rule, 84 Fed. Reg. at 32,527.
    The EPA insists that its current reading is mandated by the
    statutory text.
    It is the EPA’s current position that is wrong. Nothing in
    Section 7411(a)(1) itself dictates the “at and to the source”
    constraint on permissible ingredients of a “best system” that the
    Agency now endorses. For the EPA to prevail, its reading must
    be required by the statutory text. Peter Pan Bus Lines, 
    471 F.3d at 1354
    . It fails for at least three reasons, any of which is
    alone fatal.
    First, the plain language of Section 7411(a)(1), the root of
    the EPA’s authority to determine the best system, announces
    its own limitations. Those limitations simply do not include
    the source-specific caveat that the EPA now interposes and
    casts as unambiguous.
    Second, there is no basis—grammatical, contextual, or
    otherwise—for the EPA’s assertion that the source-specific
    language of subsection (d)(1) must be read upstream into
    subsection (a)(1) to equate the EPA’s “application of the best
    system” with the controls States eventually will apply “at and
    to” an individual source. As the EPA at times acknowledges,
    the two subsections address distinct steps in the regulatory
    process, one focused on the EPA’s role and the other focused
    on the States’. Any question as to which limitations pertain to
    each regulatory actor cannot reasonably be said to have been
    resolved by Congress in favor of the unambiguous meaning the
    EPA now advocates.
    Third, even if subsections (a)(1) and (d)(1) were read
    49
    together in the way the EPA proposes, they would not confine
    the EPA to designating a best system consisting of at-the-
    source controls. The EPA’s entire theory hinges on the
    Agency’s unexplained replacement of the preposition “for” in
    “standards of performance for any existing source” with the
    prepositions “at” and “to.” Yet the statutory text calls for
    standards of performance “for” existing sources. Emission-
    reduction measures “for” sources may readily be understood to
    go beyond those that apply physically “at” and “to” the
    individual source. Emissions trading, for example, might be a
    way “for” a source to meet a standard of performance.
    The shortcomings of its statutory interpretation are more
    than enough to doom the Agency’s claim that Section 7411
    announces an unambiguous limit on the best system of
    emission reduction. The issue is not whether the EPA’s
    counterarguments to each of these points might show its
    interpretation to be permissible as an exercise of discretion.
    Again, the EPA has not claimed to be exercising any such
    discretion here. It insists instead that the unambiguous terms
    of the statute tie its hands.
    After reviewing what Section 7411 clearly says about the
    nature and limits of the “best system of emission reduction”
    that Congress called on the EPA to determine, we take up each
    of the EPA’s arguments to show why Section 7411 does not
    unambiguously support its at-the-source restriction.
    a. Section 7411(a) Defines the Best System
    The EPA acknowledges, as it must, that Section 7411(a) is
    the source of the EPA’s authority and responsibility to
    determine the best system of emission reduction for existing
    sources and set corresponding emission guidelines. See, e.g.,
    ACE Rule, 84 Fed Reg. at 32,534. Indeed, that is the only
    subsection in which the term “best system of emission
    50
    reduction” appears. But the EPA offers no reading of
    subsection (a)(1) itself.
    Section 7411(a)(1) expresses Congress’ expectation that
    the EPA will study all “adequately demonstrated” means of
    emission reduction. And it directs the EPA to draw on
    “adequately demonstrated” methods to determine the “best”
    system to reduce emissions. Congress imposed no limits on
    the types of measures the EPA may consider beyond three
    additional criteria: cost, any nonair quality health and
    environmental impacts, and energy requirements. 
    42 U.S.C. § 7411
    (a)(1). Congress largely called on the expert judgment
    of the EPA to determine for a particular source category and
    pollutant which already-demonstrated methods compose the
    “best system.”
    Because it did not set out separate definitions for either
    “system” or “best,” those words take their ordinary meanings.
    See Sandifer v. United States Steel Corp., 
    571 U.S. 220
    , 227
    (2014). Webster’s Dictionary offers a representative definition
    of “system” contemporaneous with the Act’s adoption: “[A]
    complex unity formed of many often diverse parts subject to a
    common plan or serving a common purpose.” System,
    WEBSTER’S THIRD NEW INTERNATIONAL D ICTIONARY OF THE
    ENGLISH LANGUAGE UNABRIDGED 2322 (2d ed. 1968). The
    superlative “best” as applied to a “system of emission
    reduction” plainly places a high priority on efficiently and
    effectively reducing emissions. See Best, Merriam-Webster,
    https://www.merriam-webster.com/dictionary/best (last visited
    Jan. 11, 2021) (“excelling all others,” “offering or producing
    the greatest advantage, utility, or satisfaction”).
    The ordinary meanings of these terms “reflect[] an
    intentional effort to confer the flexibility necessary” for
    effective regulation appropriate to the context. Massachusetts
    51
    v. EPA, 
    549 U.S. 497
    , 532 (2007). As the Supreme Court has
    acknowledged, “the degree of agency discretion that is
    acceptable varies according to the scope of the power
    congressionally conferred.” Whitman v. American Trucking
    Ass’n, 
    531 U.S. 457
    , 475 (2001); see Gaughf Props., L.P. v.
    Commissioner, 
    738 F.3d 415
    , 424–425 (D.C. Cir. 2013);
    Sabre, Inc. v. Department of Transp., 
    429 F.3d 1113
    , 1122,
    1124–1125 (D.C. Cir. 2005). Congress in Section 7411
    deliberately charged the EPA with identifying the best system
    of emission reduction to keep pace with escalating threats to air
    quality, and, within expressed limits, empowered it to make the
    judgments how best to do so.
    The Agency simply ignores how the statutory text defines
    the “best system of emission reduction,” asserting instead that
    definitional language does not confer regulatory authority. See,
    e.g., EPA Br. 58–59 (“[I]t is not Section 7411(a) (‘Definitions’)
    that grants the agency authority to act.”). Section 7411(a)(1)’s
    designation as a definitional provision deprives it of standalone
    meaning, the EPA contends. The EPA instead reads it as
    “subsidiary” to Section 7411(d), regarding state standards of
    performance for existing sources. EPA Br. 58. But Congress
    does indeed use definitional provisions to confer regulatory
    authority. See, e.g., Weinberger v. Bentex Pharm, Inc., 
    412 U.S. 645
    , 652–653 (1973) (holding that the statutory definition
    of “new drug” confers authority upon the FDA). That is
    precisely what it did in Section 7411(a)(1). See Sierra Club v.
    Costle, 
    657 F.2d 298
    , 321 (D.C. Cir. 1981) (describing Section
    7411(a)(1) as authorizing the EPA to determine the best system
    of emission reduction and regulate accordingly); 40 C.F.R.
    60.22a.
    The EPA offers no support—apart from its own new-
    found version of “statutory interpretation 101,” EPA Br. 65—
    for ignoring how the Act itself defines and limits the “best
    52
    system” determination.        Nor does it offer any sound
    justification for importing language from a different provision
    governing States’ “standards of performance.” The EPA’s “at
    and to the source” limitation on “best system” finds no footing
    in the text of Section 7411(a)(1).
    b. Section 7411(d)(1) Does Not Change the Definition
    Even taking the EPA’s argument on its own terms does not
    work because Section 7411(d)(1)’s text and statutory context
    get it no further. To support its narrow reading of the EPA’s
    authority to determine the “best system,” the Agency focuses
    on the phrase “through the application of” in Section
    7411(a)(1).      That provision defines a “standard of
    performance” as an emission standard that “reflects the degree
    of emission limitation achievable through the application of the
    best system of emission reduction[.]” The EPA says the
    “application” phrase “requires both a direct object and an
    indirect object.” ACE Rule, 84 Fed. Reg. at 32,524; accord
    EPA Br. 66–68. And, it continues, Congress cannot have
    meant to leave its indirect object undefined. The EPA says that,
    grammatically speaking, someone must apply something (the
    direct object) to something else (the indirect object). EPA Br.
    115–116, 118–119. It then picks its preferred, narrow indirect
    object from a different statutory subsection and casts that
    object as the only statutorily permissible choice. See 84 Fed
    Reg. at 32,524.
    The EPA locates an indirect object in Section 7411(d).
    Unlike subsection (a)(1), subsection (d)—entitled “Standards
    of performance for existing sources”—explicates an indirect
    object. 
    42 U.S.C. § 7411
    (d). Borrowing from subsection (d),
    then, the EPA imports into subsection (a)(1) a limitation of the
    “best system of emission reduction” to measures that can be
    applied “to and at an individual existing source—i.e., any
    53
    building or facility subject to regulation.” EPA Br. 58
    (emphasis added); see also ACE Rule, 84 Fed. Reg. at 32,534.
    But the language to which the EPA points supplies the
    indirect object only of “standards of performance” adopted by
    States pursuant to Section 7411(d)(1), not of the EPA’s “best
    system of emission reduction” determined pursuant to Section
    7411(a)(1). The latter phrase does not even appear in Section
    7411(d)(1). To reach its preferred result, the Agency invokes
    surmise rather than statutory text. It insists that the limitations
    on States’ standards of performance in Section 7411(d)(1)—
    the second step in the regulatory process—must be read
    upstream to limit the EPA’s “best system of emission
    reduction” in subsection (a)(1). Nothing in the statute so
    requires.
    In the text, States’ standards of performance need only
    “reflect” the emission guidelines (or “degree of emission
    limitation achievable”) the EPA calculates based on the “best
    system of emission reduction” it determines. As laid out in the
    statute and explained above, those state-developed “standards
    of performance” follow on but are legally and functionally
    distinct from the “best system” that the EPA develops. The
    EPA is simply wrong that the statute clearly and
    unambiguously requires that the unstated indirect object of
    “application of the best system of emission reduction” under
    Section 7411(a)(1) must be the same as the indirect object of
    States’ standards of performance as stated in Section
    7411(d)(1).
    Neither does the grammatical rule the EPA invokes to
    bridge the gap between these subsections hold up. The crux of
    the EPA’s textual argument is that “the verb ‘to apply,’ requires
    both a direct object and an indirect object.” ACE Rule, 84 Fed.
    Reg. at 32,524; EPA Br. 66–68. The first obvious problem is
    54
    that, in the relevant passage of Section 7411(a)(1), Congress
    did not use the verb “apply,” but rather the noun “application.”
    The EPA acknowledges this distinction in passing in the ACE
    Rule, but dismisses it without discussion, offering only that
    “‘application’ is derived from the verb ‘to apply[.]’” 84 Fed.
    Reg. at 32,524. That is, of course, true, as far as it goes. The
    phrase “application of the best system of emission reduction”
    is what is called a nominalization, a “result of forming a noun
    or noun phrase from a clause or a verb.” Nominalization,
    Merriam-Webster         Dictionary        https://www.merriam-
    webster.com/dictionary/nominalization (last visited Jan. 11,
    2021). Grammar assigns direct or indirect objects only to
    verbs—not nouns. No objects are needed to grammatically
    complete the actual statutory phrase. So much for the
    grammatical imperative.
    Even if we were to take the EPA’s leap to the verb “apply”
    from the noun “application” that actually appears in the statute,
    the Agency comes up short. The EPA is incorrect to insist that
    the verb “apply” requires an indirect object. There is nothing
    ungrammatical about the sentence “In its effort to reduce
    emissions, the EPA applied the best system of emission
    reduction.” The verb “apply,” like its nominalization, may
    properly be used in a sentence with or without an explicit
    indirect object. See Apply, THOMAS HERBST ET AL., A
    VALENCY DICTIONARY OF ENGLISH 41–42 (Ian F. Roe et al.
    eds., 2004) (listing examples of grammatically correct uses
    with and without direct and indirect objects).6
    6
    Take, for instance, the following sentences: “It appears to
    violate GATT regulations, but the rules for applying the regulations
    are vague and the Netherlands has so far escaped censure”; “This
    information may not apply in Scotland, which has a different legal
    system.” Apply, THOMAS HERBST ET AL., A VALENCY DICTIONARY
    55
    The EPA’s shift from nominalization to verb does not, in
    any event, accomplish much. Either way, the lack of an explicit
    indirect object in Section 7411(a)(1) does not require that one
    be borrowed from Section 7411(d)(1). Equally logical indirect
    objects include, for example, the entire category of stationary
    sources, or the air pollutant to be limited. In any event, the best
    system cannot reasonably be said to be unambiguously
    applicable only to the indirect object the EPA suggests.
    The EPA faults the Clean Power Plan for reading
    “application of” to be functionally equivalent to
    “implementation of,” because “implement” “does not require
    an indirect object.” EPA Br. 73. But neither does
    “application.” So “application” textually supports adoption of
    the Clean Power Plan just as well as “implementation.” Again,
    so much for grammar mandating the EPA’s result.
    The argument fails either way, but the fact is that Congress
    used the nominalization “application of” the best system of
    emission reduction. A nominalization enables the drafter to
    leave certain information unspecified—namely, who is acting
    and where their action is directed. See, e.g., George D. Gopen,
    Who Done It? Controlling Agency in Legal Writing, Part II,
    39 LITIG . 12, 12–13 (Spring 2013) (describing how
    nominalizations create ambiguity). Legal writers, including
    Congress, employ nominalizations all the time. And they do
    so with the full awareness that their use preserves flexibility.
    Congress reasonably built in leeway for the EPA to
    OF ENGLISH 41–42    (examples from sections D1 and D5). Additional
    examples abound. See, e.g., Apply, OXFORD ENGLISH DICTIONARY
    (3d ed. 2008) (def. I.9) (“Crest bought the firm[,] and, by applying
    its marketing and distribution muscle, has turned it into a $200
    million category killer.”).
    56
    exercise technical expertise in applying Section 7411, given the
    variety of pollution problems that it covers and the importance
    of allowing States maneuvering room under the cooperative
    federalism scheme. Congress may avoid specifying subjects,
    objects, or other grammatical information because a degree of
    adaptability suits the statutory role and purpose. One way
    Congress can denote that it has delegated to an agency’s
    judgment the task of filling in the on-the-ground details of a
    statutorily defined program is by declining to dictate
    grammatically optional information, see Lehrfeld v.
    Richardson, 
    132 F.3d 1463
    , 1465–1466 (D.C. Cir. 1998);
    Appalachian Power Co. v. EPA, 
    135 F.3d 791
    , 808–810 (D.C.
    Cir. 1998), including an indirect object that the rules of
    grammar do not require be explicitly stated, see, e.g., Peter Pan
    Bus Lines, 
    471 F.3d at
    1353–1354.
    Even if an implicit indirect object can be surmised, there
    is more than one plausible candidate here, and the statute does
    not unambiguously dictate the object. There certainly is no
    rule—grammatical or otherwise—that the specific indirect
    object must be the one to which the EPA now points. At the
    least, other contextually appropriate indirect objects of the
    “best system” include the source category or the emissions.
    The EPA has failed to establish that the sole and unambiguous
    indirect object must be the individual source. The EPA, of
    course, “may fill the gap[s] the Congress left,” and any such
    “regulation is entitled to deference.” Gaughf Props., 738 F.3d
    at 424; see also Appalachian Power, 
    135 F.3d at
    811–812. But
    in the ACE Rule and in its briefing here, the EPA has
    assiduously denied the existence of any gap at all. That was
    error.
    c. EPA’s Reading Itself Falls Short
    The third and equally fatal flaw in the EPA’s textual
    57
    analysis is its unexplained substitution of the prepositions “at”
    and “to” where the text it would have us borrow from
    subsection (d)(1) actually says “for” in referencing “standards
    of performance for any existing source.” See, e.g., ACE Rule,
    84 Fed. Reg. at 32,534. As we do with any words enacted by
    Congress, we must give effect to the preposition it chose.
    Cf. Telecommunications Res. & Action Ctr. v. FCC, 
    801 F.2d 501
    , 517–518 (D.C. Cir. 1986) (finding decisive Congress’ use
    of the preposition “under” instead of “by”). The word
    Congress actually used—“for” the source—lacks the site-
    specific connotation on which the EPA’s case depends.
    In its brief, the EPA presents the compound construction
    it says inexorably follows from reading text from subsection
    (a)(1) together with text from subsection (d)(1), and says it is
    restricted to determining a “best system of emission reduction
    for any building, structure, facility, or installation.” EPA
    Br. 56 (formatting modified) (quoting 
    42 U.S.C. § 7411
    (a)(1),
    (a)(3), (a)(6), (d)(1)). The Agency then asserts that “the natural
    reading” of its proffered construction is that “the methods
    planned would be ‘for’ and act at the level of the singular,
    individual source.” 
    Id. at 62
     (emphasis added).
    In the preamble to the ACE Rule, the EPA went further,
    fully substituting the prepositions “at” and “to” in place of the
    preposition “for” that actually appears in the text the Agency
    says must be borrowed from subsection (d)(1). ACE Rule, 84
    Fed. Reg. at 32,534. It relies on that further substitution to
    insist that the best system of emission reduction designated by
    the EPA must be limited to controls “that can be applied at and
    to,” not “for,” “a stationary source.” Id.; see also id. at 32,524
    (“at”); id. at 32,532, 32,534, 32,556 (“at and to”); id. at 32,555,
    32,529 (“to and at”); id. at 32,543 (“at or to”); id. at 32,526 n.65
    (“to or at”); EPA Br. 4, 58, 74. But nowhere in the ACE Rule
    does the EPA explain this swap of one preposition for two
    58
    meaningfully more restrictive ones. See, e.g., 84 Fed. Reg. at
    32,523–32,524, 32,534–32,535.
    The EPA rewrites rather than reads the plain statutory text.
    Section 7411(a)(1), even if cross-referenced to subsection
    (d)(1) in the way the EPA says it must be, calls for the Agency
    to determine “the degree of emission limitation achievable
    through the application of the best system of emission
    reduction for any existing source”—not the application of the
    best system “at” and “to” such a source. And the word “for”
    lacks the physical on-site connotation that is so critical to the
    EPA’s reading of the statutory text. Indeed, a standard of
    performance or system of emission reduction “for” a source
    just means that the system is “with regard or respect to” or
    “concerning” the source.        See For, OXFORD ENGLISH
    DICTIONARY (2d ed. 1989) (def. 26). In contrast, “at” and “to”
    tend to connote direct physical proximity or contact. See At,
    OXFORD ENGLISH D ICTIONARY (3d ed. 2008) (def. 1.a)
    (“usually determining a point or object with which a thing or
    attribute is practically in contact”); To, OXFORD ENGLISH
    DICTIONARY (3d. ed 2008) (def. 5.a) (“Into (or in) contact with;
    on, against”). A best system “for” a source thus might entail a
    broader array of controls that concern but are not immediately
    physically proximate to the source—such as, for instance,
    generation shifting.
    ***
    In sum, the straitened vision of the EPA’s best system that
    the Agency espies in Section 7411 is simply not supported by
    the text, let alone plainly and unambiguously required by it.
    The Act calls on the EPA to determine the degree of emission
    limitation achievable through “application of the best system
    of emission reduction” without specifying the system’s indirect
    object, and uses the preposition “for” when it calls on the States
    59
    to develop “standards of performance for existing sources.” 
    42 U.S.C. § 7411
    (a), (d). It simply does not unambiguously bar a
    system of emission reduction that includes generation shifting.
    The EPA’s position depends critically on words that are
    not there. It erroneously treats a nominalization of a verb as
    requiring an indirect object, collapses two separate functions
    and provisions of the Act in order to supply a borrowed indirect
    object, does so without any evidence that the borrowed indirect
    object was what Congress necessarily intended, and narrowly
    focuses the Agency’s authority on that indirect object by using
    a different preposition from the one that actually appears in the
    borrowed text. Each of those interpretive moves was a misstep.
    Read faithfully, Section 7411(a)(1) lacks the straitjacket that
    the EPA imposes.
    Policy priorities may change from one administration to
    the next, but statutory text changes only when it is amended.
    The EPA’s tortured series of misreadings of Section 7411
    cannot unambiguously foreclose the authority Congress
    conferred. The EPA has ample discretion in carrying out its
    mandate. But it may not shirk its responsibility by imagining
    new limitations that the plain language of the statute does not
    clearly require.
    2. Statutory History, Structure, and Purpose
    Even looking beyond the text does nothing to substantiate
    the EPA’s proposed reading of Section 7411. See Kiewit
    Power Constructors Co. v. Secretary of Labor, 
    959 F.3d 381
    ,
    395 (D.C. Cir. 2020) (Henderson, J.) (“To discern the
    Congress’s intent, we generally examine the statutory text,
    structure, purpose and its legislative history.”) (quoting
    Lindeen v. SEC, 
    825 F.3d 646
    , 653 (D.C. Cir. 2016)). These
    other tools of statutory interpretation underscore the flexibility
    60
    of Section 7411(a)’s text, not the cabined reading the EPA
    proposes.
    We begin by acknowledging Section 7411’s role within
    the Clean Air Act. It is a catch-all, intended to ensure that the
    Act achieves comprehensive pollution control by guaranteeing
    that there are “no gaps in control activities pertaining to
    stationary source emissions that pose any significant danger to
    public health or welfare.” S. REP. NO. 91-1196, at 20 (1970).
    In other words, Section 7411 is intended to reach pollutants that
    do not fit squarely within the ambit of the Act’s other
    regulatory provisions. It authorizes regulation of pollutants not
    controlled by the other programs under the Act. The EPA does
    not contest that greenhouse gases emitted by powerplants fit
    that description.
    The Agency points to statutory structure and history for
    evidence that Congress restricted the “best system of emission
    reduction” under Section 7411(a) to physical controls that are
    applied “at and to” an existing source. But the history and
    structure only confirm what the text shows: Nothing the EPA
    has identified suggests that Congress in Section 7411 meant to
    so constrict what might be part of a “best system of emission
    reduction.”
    The Congress that enacted Section 7411 was well aware
    that what a “best system” might comprise is necessarily
    dynamic and evolving. Congress’ main limitation was that the
    “best system” selected by the EPA must be “adequately
    demonstrated.” 
    42 U.S.C. § 7411
    (a)(1). And it stated three
    other key criteria—cost, nonair quality health and
    environmental impact, and energy requirements—as factors
    the EPA must take into account. See 
    id.
     With those parameters
    in place, Congress largely left the identification of the best
    61
    system of emission reduction to the Agency’s expert scientific
    judgment.
    Consider cues from the Clean Air Act as a whole. In
    contrast to other systemic benchmarks in the Act,
    Section 7411(a)(1)’s prescription of the “best system of
    emission reduction” is striking for its paucity of restrictive
    language. References to more specific categories of emission-
    reduction tools appear elsewhere in the Act. A provision
    governing the Nitrogen Oxides Emissions Reduction Program,
    for example, directs the Administrator to establish limits based
    on the “degree of reduction achievable through the retrofit
    application of the best system of continuous emission
    reduction, taking into account available technology[.]” 42
    U.S.C. § 7651f(b)(2) (emphasis added). The Act’s regional
    haze program is likewise specific in its call for use of the “best
    available retrofit technology.” Id. § 7491(b)(2)(A), (g)(2). The
    specificity of those other provisions highlights the comparative
    generality of Section 7411(a)’s reference to the “best system of
    emission reduction.”
    The sole provision the EPA highlights to shore up its at-
    the-source theory only further undermines it. The EPA points
    to the Act’s Prevention of Significant Deterioration (PSD)
    program, 
    42 U.S.C. § 7475
    , and its requirement of controls at
    least as stringent as limits set under Section 7411, see
    
    id.
     § 7479(3), to argue that that “the interrelationship between
    the two types of standards”—the best system of emission
    reduction and the best available control technology—“is only
    intelligible if the standards are in pari materia.” EPA Br. 85.
    But the distinct roles of the two provisions make clear that the
    limits in Section 7475 have no place in Section 7411(a)(1).
    To qualify for a permit under the PSD program before a
    source may be built or modified, an applicant must affirm that
    62
    it will apply to each source the “best available control
    technology,” or BACT, to limit its emissions. 
    42 U.S.C. § 7475
    (a)(4). The statute defines BACT as the degree of
    control that the permitting agency “determines is achievable for
    such [major emitting] facility through application of
    production processes and available methods, systems, and
    techniques, including fuel cleaning, clean fuels, or treatment or
    innovative fuel combustion techniques[.]” 
    Id.
     § 7479(3). The
    statute further provides that BACT cannot “result in emissions
    of any pollutants which will exceed the emissions allowed by
    any applicable standard established pursuant to [S]ection 7411
    or 7412 of this title.” Id. § 7479(3). The listed BACT options,
    EPA observes, are all physically applicable to the source unit.
    EPA Br. 85.
    But the EPA ignores a critical detail: The BACT
    requirement applies only to newly constructed or modified
    sources. See Alaska Dep’t of Env’t Conservation v. EPA, 
    540 U.S. 461
    , 472 (2004) (describing 
    42 U.S.C. § 7475
    ). Any
    standard established under Section 7411 and also “applicable,”
    per the statutory cross-reference, to a facility regulated for
    prevention of significant deterioration under Section 7475
    would be a standard for new or modified sources established
    pursuant to Section 7411(b). The BACT requirement does not
    apply to the existing sources covered by the provision at issue
    here, Section 7411(d). See New York v. EPA, 
    413 F.3d 3
    , 13
    (D.C. Cir. 2005). Even if Section 7475 tracks Section 7411(b),
    there is simply no conflict between, on one hand, requiring new
    source construction to employ the newest and best at-the-
    source control technologies and, on the other, empowering the
    EPA to look to a wider range of ways to reduce emissions when
    it regulates older, existing sources.
    The anomaly of looking to Section 7475(a)(4) to confine
    Section 7411 is highlighted by the fact that BACT permits are
    63
    required only in so-called “non-attainment” areas of the
    country. See 
    42 U.S.C. §§ 7407
    , 7472, 7474. We are
    unpersuaded that Congress buried a limit on the EPA’s
    Section 7411 authority to address pollution from existing
    sources throughout the Nation by making reference to a floor
    for certain new facilities in certain parts of the country.
    The statutory history of the BACT requirement further
    demonstrates that Congress did not intend that it weaken
    Section 7411(d). Sections 7475 and 7479 were enacted in the
    1977 Clean Air Amendments, Pub. L. No. 95-95, §§ 165, 169,
    
    91 Stat. 685
    , 735–742 (Aug. 7, 1977). In the very same
    legislation, Congress restricted the best system of emission
    reduction for new sources to technological methods while
    explicitly allowing the best system for existing sources to
    include non-technological methods. § 109(c)(1)(A), 91 Stat.
    at 700. If Congress wanted to confine Section 7411 to at-the-
    source technologies, it would have done so directly rather than
    hiding such a substantial limitation in an implicit inference
    from a more remote statutory provision.
    The Clean Air Act’s legislative history, including the
    history of the 1970 enactment of Section 7411 and the 1977
    and 1990 amendments, further shows that Congress never
    imposed on the “best system of emissions reduction” the
    constraints the EPA now advocates. Before Congress settled
    on the best-system language it enacted in 1970, the Senate bill
    proposed to authorize the EPA to set standards for stationary
    sources “reflect[ing] the greatest degree of emission control”
    achievable through “the latest available control technology,
    processes, operating methods, or other alternatives.” S. 4358,
    91st Cong. § 6 (1970). The phrase “other alternatives” was
    understood to encompass “[t]he maximum use of available
    means of preventing and controlling air pollution”—without
    limitation to technological or at-the-source means. S. REP. NO.
    64
    91-1196, at 16. The Senate believed that was “essential” to
    limit emissions from both new and existing sources. Id. The
    House, for its part, proposed an initial version of Section 7411
    that would have “require[d] new sources to ‘prevent and
    control [their] emissions to the fullest extent compatible with
    the available technology and economic feasibility,’” H.R.
    17255, 91st Cong. § 5 (1970), but included no provision
    regarding the regulation of existing sources.
    As enacted, Section 7411 simply requires that the EPA
    identify as its benchmark for existing sources the “best system
    of emission reduction.” 
    42 U.S.C. § 7411
    (a)(1). Nothing that
    the EPA identifies or that we discern in the relevant history
    shows the enacting Congress myopically “focused on steps that
    can be taken at and by individual sources to reduce emissions.”
    EPA Br. 69. And of course, even if Congress at that time was
    only thinking of at-the-source controls, the EPA was well
    aware that environmental problems and their solutions rapidly
    evolve. At the end of the day, it is the statutory text that
    governs. See Bostock v. Clayton County, 
    140 S. Ct. 1731
    , 1738
    (2020).
    Congress has consistently relied on the EPA’s expert
    judgment in identifying the “best system” for existing sources.
    Its action in making, and then undoing, a limiting amendment
    to Section 7411’s “best system of emission reduction” just for
    new and modified sources—not existing sources—underscores
    the point. First, Congress in 1977 amended the standard for
    new sources to require use of “the best technological system of
    continuous emission reduction,” but did not make any parallel
    change to the standard for existing sources to add those
    “technological” and “continuous” limitations. Clean Air
    Amendments Act of 1977, Pub. L. No. 95-95, § 109(c)(1)(A),
    
    91 Stat. 685
    ; see also 
    id. at 700
     (adding Section 7411(a)(1)(C)).
    Then, in 1990, Congress again amended Section 7411, this time
    65
    to remove those additional limitations, reverting for new
    sources to the “best system of emission reduction” that had
    applied all along to existing sources. Clean Air Act
    Amendments of 1990, Pub. L. No. 101-549, § 403(a), 
    104 Stat. 2399
    , 2631 (1990).
    The amendment and re-amendment of the new-source
    “best system” language emphasizes that Congress consistently
    avoided imposing any such technological, at-the-source
    limitation on the measures that EPA might include in the “best
    system” for reducing emissions from existing-source
    categories. And it shows that Congress had always understood
    the existing-source “best system” language to go beyond the
    technological restrictions that it briefly imposed on the parallel
    new source provision.
    The ACE Rule is the first EPA rule to read the statute as
    so strictly boxing in the Agency. Although agency practice
    cannot directly show whether Congress had a specific intent on
    the matter in question, it is notable that the regulators closest to
    the issue never before saw what the EPA now insists is obvious
    on the face of Section 7411.
    Over the last half century, no prior Administrator read the
    Act to foreclose from consideration in the “best system” all but
    at-the-source means of emission control. Rather, the EPA has
    exercised latitude to consider any adequately demonstrated
    approach to reducing harmful pollutants from existing source
    categories that it believed met the cost, grid-reliability and
    other statutory criteria. 
    42 U.S.C. § 7411
    (a)(1). Where the
    characteristics of the source category and the pollutant at issue
    point to emissions trading programs or production shifts from
    higher- to lower-emitting sources as components of the “best
    system,” the EPA has in the past consistently concluded that it
    had the authority to consider them.
    66
    During the administration of President George W. Bush,
    for example, the EPA adopted the Clean Air Mercury Rule, 
    70 Fed. Reg. 28,606
     (May 18, 2005), which included a mercury
    cap-and-trade program as a component of its best system of
    emissions reduction for existing coal-fired power plants, see 
    id. at 28
    ,619–28,620; 
    id. at 28,617
     (“EPA has determined that a
    cap-and-trade program based on control technology available
    in the relevant timeframe is the best system for reducing
    [mercury] emissions from existing coal-fired Utility Units.”). 7
    The EPA’s Clinton-era regulation of nitrogen oxide
    emissions from municipal solid waste combustors likewise
    relied on Section 7411(d), together with the EPA’s waste-
    management authority under Section 7429, to authorize States
    to include emissions-trading programs in their State Plans. 
    40 C.F.R. § 60
    .33b(d)(2). Under state standards of performance
    designed to meet guidelines the EPA derived from its “best
    system,” regulated entities were permitted to average the
    emission rates of multiple units within a single plant as well as
    trade emission credits with other plants. Municipal Waste
    Combustors Rule, 
    60 Fed. Reg. 65,387
    , 65,402 (Dec. 19,
    1995).
    The EPA’s efforts to distinguish those other
    Section 7411(d)(1) programs do not work. The EPA claims
    that the Mercury Rule did not primarily rely on a cap-and-trade
    7
    We vacated the Mercury Rule for unlawfully delisting
    mercury-emitting electric utility steam generating units from the
    Section 7412 Hazardous Air Pollutants list. See New Jersey v. EPA,
    
    517 F.3d 574
    , 582–584 (D.C. Cir. 2008). Because we held those
    mercury sources must be listed, and because Section 7411 cannot be
    used to regulate air pollutants listed under Section 7412, the existing-
    source rule the EPA had adopted under Section 7411(d) to control
    those same mercury emissions from power plants failed as well.
    67
    or dispatch shifting program, but rather that the best system
    rested on a “combination of a cap-and-trade mechanism
    and * * * the technology needed to achieve the chosen cap
    level.” EPA Br. 72 n.20 (quoting ACE Rule, 84 Fed. Reg. at
    32,526). To be clear, that sort of hybrid best system, involving
    both on-site and system-wide elements, is precisely what the
    EPA now insists is unprecedented and expressly barred by the
    statute’s text.
    Lest there be any doubt that the Mercury Rule’s best
    system rested in significant part on the cap-and-trade
    mechanism, we note that the EPA in fact approved state
    implementation plans that adopted none of the on-site controls
    included in the best system and instead relied entirely on
    implementation of the best system’s cap-and-trade program.
    See, e.g., Notice of Intent, 
    32 La. Reg. 869
    , 870 (May 20, 2006)
    (proposing an implementation plan solely reliant on cap-and-
    trade); Approval and Promulgation of State Plan for
    Designated Facilities and Pollutants: Louisiana, 
    72 Fed. Reg. 46,188
    , 46,188 (Aug. 17, 2007) (approving Louisiana’s
    proposal on the basis that it “would meet [Clean Air Mercury
    Rule] requirements by participating in the EPA administered
    cap-and-trade program addressing [mercury] emissions”).
    Contrary to the EPA’s assertions, e.g. EPA Br. 4, the Agency
    plainly has previously embraced beyond-the-source measures
    of emission reduction as authorized by the statutory text.
    The EPA’s invocation of its own past practice under
    Section 7411 falls wide of the mark. It errs in insisting that
    “the more than seventy Section 7411 rules” promulgated for
    “roughly forty-five years” somehow reflect a consistent
    adherence to the Agency’s new view. EPA Br. 4, 88; see 
    id.
     at
    37–38, 88–89; ACE Rule, 84 Fed. Reg. at 32,526. Almost all
    of the rules to which it refers are irrelevant to the issue at hand.
    They were for new sources, subject to Section 7411(b), not
    68
    existing sources under Section 7411(d). See 84 Fed. Reg. at
    32,526.
    Older facilities that may be capable only of outdated, more
    polluting methods of generation present different regulatory
    challenges than new sources.           As discussed above in
    connection with the EPA’s reference to BACT requirements
    for new-source permitting under the PSD program, a
    requirement that owners and operators constructing new
    facilities apply state-of-the-art, lowest-emitting equipment and
    methods “at and to the source” might well be the best available
    means of reducing emissions for that source category. The
    same cannot be said for existing sources. A central error of the
    ACE Rule is that it fails to appreciate that difference. It
    identifies a handful of measures applicable to and at the source
    that the EPA suggests may achieve slight reductions. But
    industry practice demonstrates that better, lower-emitting,
    reliable, and cost-effective systems for reducing emissions
    from existing power plants typically also shift generation away
    from higher-emitting, fossil-fuel-fired capacity when
    renewable or lower- or zero-emitting generation is an available
    substitute.
    Because the best, most efficient and effective systems for
    controlling emissions from existing sources ordinarily differ
    from the best systems for new sources, they are regulated via a
    distinct statutory track. Only the Section 7411(d) rules are
    relevant to the EPA’s prior understanding of its authority to
    regulate existing sources. Those prior EPA rules contradict the
    EPA’s position here. Before its about-face in the ACE Rule,
    all three of the Agency’s most recent Section 7411(d) rules
    included emissions trading or generation shifting to lower-
    emitting sources. See Clean Power Plan, 80 Fed. Reg. at
    64,755–64,756; Clean Air Mercury Rule, 70 Fed. Reg. at
    69
    28,606, 28,617, 28,619–28,620; Municipal Waste Combustors
    Rule, 
    60 Fed. Reg. 65,387
    , 65,402 (Dec. 19, 1995).
    To put the EPA’s mistaken reading of Section 7411 in
    perspective, consider how it effectively relegates federal
    regulators back to the sidelines where they stood before
    Congress overhauled the Clean Air Act in 1970. The federal
    government had until then done little more than provide
    information and guidance to cheer on States’ air-quality
    regulators. See Train v. NRDC, 
    421 U.S. 60
    , 64 (1975) (noting
    that the States’ response to earlier iterations of the Act focused
    on information and incentives had been “disappointing”).
    With the 1970 amendments, a virtually unanimous
    Congress dramatically strengthened the federal government’s
    hand in combatting air pollution. See Train, 
    421 U.S. at 64
    (“These Amendments sharply increased federal authority and
    responsibility. * * * The difference * * * was that the States
    were no longer given any choice as to whether they would meet
    th[eir statutory] responsibility.”); cf. EPA v. EME Homer City
    Generation, LP, 
    572 U.S. 489
    , 497 (2014) (noting this
    progression toward “increasing[ly] rigor[ous]” federal
    regulation of interstate air pollution). Congress did so “to
    protect and enhance the quality of the Nation’s air resources so
    as to promote the public health and welfare and the productive
    capacity of its population[.]” 
    42 U.S.C. § 7401
    (b)(1). The
    EPA’s newly enhanced authority was “designed to provide the
    basis” for “a massive attack on air pollution.” S. REP. NO . 91-
    1196, at 1. Section 7411(d) ensured that there would be “no
    gaps in control activities pertaining to stationary source
    emissions that pose any significant danger to public health or
    welfare.” 
    Id. at 20
    .
    Describing the Act shortly before its passage, Republican
    Senator John Cooper explained that the “philosophy of the bill
    70
    abandons the old assumption of requiring the use of only
    whatever technology is already proven and at hand” and
    instead “set[s] out what is to be achieved.” 116 CONG. REC.
    32,919 (1970). To that end, the Act did not finely detail
    specific approaches to enumerated sources or types of air
    pollution. See 116 CONG. REC. 32,901–32,902 (1970)
    (statement of Sen. Muskie). Congress chose instead to entrust
    the EPA with flexible powers to craft effective solutions. Only
    by doing so could air quality regulation hope to reflect
    developing understandings of escalating problems and bring to
    bear as-yet-unseen solutions.
    American air quality is the proof of that approach. The
    EPA has worked closely with industry, States, and the public
    to develop the world’s most nimble, responsive, and effective
    regime of air pollution regulation. For example, in the half-
    century since the 1970 Act, “the combined emissions
    of * * * six key pollutants regulated under the National
    Ambient Air Quality Standards dropped by 73 percent”
    between 1970 and 2017. EPA Releases 2018 Power Plant
    Emissions Demonstrating Continued Progress, EPA (Feb. 20,
    2019), https://www.epa.gov/newsreleases/epa-releases-2018-
    power-plant-emissions-demonstrating-continued-progress
    (last visited Jan. 11, 2021).
    The EPA’s new reading of Section 7411 would atrophy the
    muscle that Congress deliberately built up. The EPA asserts it
    lacks authority to curb a pollutant that the Agency itself has
    repeatedly deemed a grave danger to health and welfare but that
    eludes effective control under other provisions of the Act. We
    do not believe that Congress drafted such an enfeebled gap-
    filling authority in Section 7411.
    ***
    71
    In sum, traditional tools of statutory interpretation reveal
    nothing in the text, structure, history, or purpose of
    Section 7411 that compels the reading the EPA adopted in the
    ACE Rule.
    3. Compliance Measures
    In the ACE Rule, the EPA also limited the measures that
    sources may use to comply with the States’ standards of
    performance set under Section 7411(d). Recognizing that
    sources generally have “broad discretion” in how they comply
    with state standards, 84 Fed. Reg. at 32,555, the EPA
    nonetheless categorically excluded two specific measures from
    the States’ consideration: averaging and trading, and biomass
    co-firing. It did so on the ground that these measures do not
    meet two criteria it determined were required of compliance
    measures: that they be (1) “capable of being applied to and at
    the source” and (2) “measurable at the source using data,
    emissions monitoring equipment or other methods to
    demonstrate compliance[.]” Id. The EPA identified these
    criteria on account of “both legal and practical concerns[.]” Id.
    The Agency’s legal concern was that non-source-specific
    compliance measures “would be inconsistent with the EPA’s
    interpretation of the” best system of emission reduction as itself
    plant-specific. ACE Rule, 84 Fed. Reg. at 32,555–32,556. In
    that way, the EPA extended to States’ compliance measures the
    same incorrect textual interpretation of the Clean Air Act that
    underlay its determination of what best systems may include—
    namely, that the system must be one that can be applied to and
    at the individual source.           The EPA reasoned that
    “implementation and enforcement of such standards should
    correspond with the approach used to set the standard in the
    first place.” Id. at 32,556.
    72
    The Agency’s practical concern was that compliance
    measures that are not source-specific could result in
    “asymmetrical regulation[,]” meaning the stringency of
    standards could vary across sources. ACE Rule, 84 Fed. Reg.
    at 32,556. It argues here that such regulation “could have
    significant localized adverse consequences” in the case of
    many pollutants regulated under Section 7411(d). EPA Br.
    240.
    Because we hold that the EPA erred in concluding Section
    7411 unambiguously requires that the best system of emission
    reduction be source specific, we necessarily reject the ACE
    Rule’s exclusion from Section 7411(d) of compliance
    measures it characterizes as non-source-specific. The Agency
    tied that exclusion to its flawed interpretation of the statute as
    unambiguously confined to measures taken “at” individual
    plants, so it falls with that decision. ACE Rule, 84 Fed. Reg.
    at 32,555–32,556.
    The statute says nothing about the measures that sources
    may use to comply with the standards States establish under
    Section 7411(d), and the EPA cites no separate authority that
    would require compliance measures to be source-specific, or
    that Congress meant to so hogtie the States in devising
    standards of performance. Regardless of any policy-based
    reasons the EPA offers for limiting compliance measures, then,
    its decision to exclude averaging and trading and biomass
    co-firing is foreclosed by its legally erroneous starting point.
    Neither can the EPA’s policy-based reasons sustain its
    decision to exclude its disfavored non-source-specific
    compliance measures in the context of carbon dioxide
    emissions. Apart from its statutory interpretation, the EPA’s
    only ground for excluding those compliance measures is the
    Agency’s stated concern to avoid asymmetrical regulation.
    73
    ACE Rule, 84 Fed. Reg. at 32,556. It argues that asymmetrical
    regulation “could have significant localized adverse
    consequences for public health and the environment.” EPA Br.
    240. The Agency points to the case of fluoride—another
    pollutant regulated under Section 7411(d)—to note that
    allowing sources to meet state standards of performance by
    averaging emissions across units or between facilities “could
    cause serious environmental impacts on local communities
    where pollution was under-controlled, causing localized
    damage.” Id. In light of such considerations, the EPA worried
    that a system of averaging and trading “would undermine the
    EPA’s determination” of the best system of emission reduction,
    leading to the sort of localized consequences the system is
    designed to guard against. ACE Rule, 84 Fed. Reg. at 32,557.
    But that point does not support the EPA’s categorical rule,
    let alone prove that the statute unambiguously compels the
    Agency’s reading. Unlike pollutants such as fluoride, carbon
    dioxide emissions do not pose localized concerns at the site of
    emission. Whereas the EPA might determine that the best
    system for reducing fluoride emissions is one that can be
    applied to and at the source, and it would be reasonable for the
    EPA in turn to limit compliance measures to correspond with
    such a “best system,” the same cannot be said of carbon
    dioxide. Indeed, the EPA recognizes that “CO2 is a global
    pollutant with global effects[,]” meaning “there may be few
    direct and area public health consequences from asymmetrical
    regulation of carbon dioxide within a State.” EPA Br. 239.
    The Agency defends its concern about asymmetrical
    regulation in the context of carbon dioxide emissions with the
    unsupported contention that an interpretation of Section
    7411(d) that allowed non-source-specific compliance measures
    “would not be limited to carbon dioxide alone.” EPA Br. 240.
    But there is no reason to conclude, and petitioners do not argue,
    74
    that the statute requires the EPA to permit non-source-specific
    compliance measures for every pollutant it regulates under
    Section 7411. The statute is not so rigid as EPA supposes. In
    fact, Section 7411 itself does not textually restrict the States’
    choice of compliance measures for their sources at all. See also
    Power Cos. Pet’rs Br. 25–26; Biogenic Pet’r Br. 16–17. Even
    if the EPA might reasonably limit compliance measures in
    specific situations based on its determination of the best system
    for reducing particular types of emissions with localized
    consequences, the statute imposes no requirement that such
    limitations be uniform across the regulation of different
    pollutants.
    In sum, the EPA’s conclusion on compliance by sources
    rises and falls with its legally flawed interpretation of the
    statute. The Agency’s practical concern about asymmetrical
    regulation could not, in any event, support the exclusion of
    biomass co-firing or averaging and trading in the particular
    context of carbon dioxide emission regulation.
    B. T HE MAJOR QUESTIONS D OCTRINE
    The EPA also references the so-called “major questions”
    doctrine in defense of its statutory interpretation and the ACE
    Rule. 84 Fed. Reg. at 32,529. But that doctrine does not
    confine the EPA to adopting solely emission standards that can
    be implemented physically to and at the individual plant.
    The Supreme Court has said in a few cases that sometimes
    an agency’s exercise of regulatory authority can be of such
    “extraordinary” significance that a court should hesitate before
    concluding that Congress intended to house such sweeping
    authority in an ambiguous statutory provision. See King v.
    Burwell, 
    576 U.S. 473
    , 485–486 (2015); Gonzales v. Oregon,
    
    546 U.S. 243
    , 262, 266–267 (2006); FDA v. Brown &
    Williamson Tobacco Corp., 
    529 U.S. 120
    , 159 (2000); accord
    75
    Utility Air Regulatory Group v. EPA (UARG), 
    573 U.S. 302
    ,
    324 (2014); see also MCI Telecommc’ns v. AT&T, 
    512 U.S. 218
    , 231 (1994). Where there are special reasons for doubt, the
    doctrine asks whether it is implausible in light of the statute and
    subject matter in question that Congress authorized such
    unusual agency action. See, e.g., UARG, 573 U.S. at 324
    (considering whether the challenged rule would “bring about
    an enormous and transformative expansion in EPA’s
    regulatory     authority      without     clear      congressional
    authorization”); Brown & Williamson, 
    529 U.S. at 161
     (holding
    that the FDA could not regulate tobacco because it was “plain
    that Congress ha[d] not given the FDA the authority that it
    s[ought] to exercise”).
    In the ACE Rule, the EPA stated that, while its
    interpretation of Section 7411 did not depend on the “major
    question[s] doctrine[,]” the Agency believed that “that doctrine
    should apply here[.]” 84 Fed. Reg. at 32,529. The Agency
    reasoned that the Clean Power Plan would have had “billions
    of dollars of impact on regulated parties and the economy,”
    would have “affected every electricity customer[,]” was
    “subject to litigation involving almost every State,” and would
    have upset the balance of regulatory authority between federal
    agencies and the States. Id. For those reasons, the Agency
    concluded that the “interpretive question raised”—whether the
    “best system of emission reduction” can include measures
    other than improvements to and at the physical source—“must
    be supported by a clear[]statement from Congress.” Id. That
    was incorrect.
    1. The EPA’s Regulatory Mandate
    Unlike cases that have triggered the major questions
    doctrine, each critical element of the Agency’s regulatory
    76
    authority on this very subject has long been recognized by
    Congress and judicial precedent.
    Most importantly, there is no question that the regulation
    of greenhouse gas emissions by power plants across the Nation
    falls squarely within the EPA’s wheelhouse. The Supreme
    Court has ruled specifically that greenhouse gases are “air
    pollutants” covered by the Clean Air Act. Massachusetts v.
    EPA, 
    549 U.S. at 532
    . More to the point, the Court has told the
    EPA directly that it is the Agency’s job to regulate power
    plants’ emissions of greenhouse gases under Section 7411.
    “Congress delegated to EPA the decision whether and how to
    regulate carbon-dioxide emissions from powerplants” through
    a “§ 7411 rulemaking[.]” AEP, 
    564 U.S. at
    426–427. The
    separate opinion agrees. See Separate Op. at 14 (“Does the
    Clean Air Act direct the EPA to make our air cleaner? Clearly
    yes. Does it require at least some carbon reduction? According
    to Massachusetts v. EPA, again yes.”).
    On top of that, the issuance of regulations addressing
    greenhouse gas pollution is mandatory under the statute
    because of longstanding endangerment findings.               In
    Massachusetts v. EPA, the Supreme Court directed the EPA
    either to make an endangerment finding under the statute for
    greenhouse gas pollution, or to explain why it would not do so.
    
    549 U.S. at
    532–535. The EPA complied. For now more than
    a decade—from 2009 to the present day in the ACE Rule
    itself—the EPA has consistently and repeatedly recognized the
    serious danger that greenhouse gas pollution poses to human
    health and welfare. See ACE Rule, 84 Fed. Reg. at 32,533;
    New Source Rule, 80 Fed. Reg. at 64,530–64,531; 2009
    Endangerment Finding, 74 Fed. Reg. at 66,496–66,497. By
    statute, that finding triggers a mandatory duty on the EPA to
    regulate greenhouse gas pollution. 
    42 U.S.C. § 7521
    (a)(1)
    (motor vehicle emissions); 
    42 U.S.C. § 7411
    (b) (stationary
    77
    sources that contribute significantly to such dangerous
    pollution).8
    So the EPA has not just the authority, but a statutory duty,
    to regulate greenhouse gas pollution, including specifically
    from power plants.
    In that way, the pollution measures in the Clean Power
    Plan do not fit the major-question mold of prior cases. For
    example, in Brown & Williamson, the major question was
    whether the agency had authority to regulate tobacco at all.
    There, the Supreme Court ruled that there was “reason to
    hesitate” before concluding that the provisions of the Food,
    Drug, and Cosmetic Act covering restricted devices, Brown &
    Williamson, 
    529 U.S. at
    134 (citing 21 U.S.C. § 360j(e)), gave
    the Food and Drug Administration the authority to regulate
    8
    As discussed below with respect to the challenge brought by
    the Coal Petitioners (infra at III.A.1), the legal basis for the EPA’s
    regulation of greenhouse gas emissions from existing power plants
    in both the Clean Power Plan and the ACE Rule was the Agency’s
    prior 2015 decision to issue standards of performance for carbon
    dioxide emitted from new power plants. That decision, in turn, was
    based on the Agency’s recognition (since the 1970s) that fossil-fuel-
    fired power plants contribute significantly to air pollution, which
    “may reasonably be anticipated to endanger the public health or
    welfare.” 
    42 U.S.C. § 7411
    (b)(1)(A); see Air Pollution Prevention
    and Control: List of Categories of Stationary Sources, 
    36 Fed. Reg. 5931
    , 5931 (March 31, 1971); Air Pollution Prevention and Control:
    Addition to the List of Categories of Stationary Sources, 
    42 Fed. Reg. 53,657
    , 53,657 (Oct. 3, 1977). The EPA also determined in 2015
    that power plants contribute significantly to greenhouse gas pollution
    in particular. See New Source Rule, 80 Fed. Reg. at 64,531. That
    determination, combined with the determination that greenhouse
    gases are dangerous to public health and welfare, triggers a
    mandatory duty to regulate under Section 7411(b)(1)(A).
    78
    tobacco given its “unique political history” and its role as a
    “significant portion of the American economy.” Id. at 159.
    The Court reasoned based on the overall drug-regulatory
    scheme, as well as Congress having “created a distinct
    regulatory scheme for tobacco products,” that Congress “could
    not have intended to delegate a decision of such economic and
    political significance to an agency in so cryptic a fashion.” Id.
    at 159–160.
    That question of agency authority to regulate the matter in
    question was absent for the Clean Power Plan. In fact, the
    Supreme Court in Massachusetts v. EPA rejected the analogy
    between regulation of greenhouse gases as a pollutant under the
    Clean Air Act and regulation of tobacco as a drug under the
    Food, Drug, and Cosmetic Act. 
    549 U.S. at
    530–531. Treating
    tobacco as a drug would have been wholly novel, requiring the
    agency to ban virtually all tobacco products—a result the Court
    suspected Congress did not intend. 
    Id. at 531
    ; Brown &
    Williamson, 
    529 U.S. at 143
    . By contrast, the Supreme Court
    explained, greenhouse gases are air pollutants that fall squarely
    within the Clean Air Act’s coverage, and the Act would subject
    such pollutants, if the agency makes the necessary findings,
    only to regulation, not prohibition. Massachusetts v. EPA, 
    549 U.S. at 531
    .
    The Clean Air Act also contains its own limits on
    regulation, like mandating that the EPA take into account such
    factors as available technology and the cost of compliance. 
    Id.
    (citing 
    42 U.S.C. § 7521
    (a)(2)); see also 
    42 U.S.C. § 7411
    (a)(1) (requiring consideration of health and
    environmental impacts, energy requirements, and cost). In that
    way, Congress designed the Clean Air Act’s processes for
    regulating air pollution to adapt to “changing circumstances
    and scientific developments” without imposing unreasonable
    technological or financial burdens on industry. Massachusetts
    79
    v. EPA, 
    549 U.S. at 532
    . So, unlike the major question of
    tobacco regulation in Brown & Williamson, there is “nothing
    counterintuitive” about the EPA’s reasonable regulation of
    dangerous airborne substances like greenhouse gases. 
    Id.
     at
    531–532.
    Similarly, the major question in UARG was whom the
    EPA was attempting to regulate. In that case, the Supreme
    Court held that the EPA’s statutory permitting authority for the
    construction and modification of stationary sources was
    “designed to apply to, and cannot rationally be extended
    beyond, a relative handful of large sources capable of
    shouldering heavy substantive and procedural burdens”—
    sources like power plants. 573 U.S. at 322. The Court held
    that, without clear statutory grounding, the EPA’s effort to
    extend permitting requirements to literally millions of small
    sources of greenhouse gas pollution but of no other regulated
    pollutants—sources like schools, hospitals, churches, and
    shopping malls—overshot its statutory authority. Id. at 324,
    328.
    The Clean Power Plan, by contrast, regulated the very
    entities the EPA was told by the Supreme Court in AEP and
    UARG to regulate—fossil-fuel-fired power plants. And it
    employed statutory tools that were “suitable” for application to
    the long-regulated power industry. See UARG, 573 U.S. at
    323, 324 n.7. American Electric Power pointed the Agency to
    regulation under Section 7411 specifically, explaining that
    “Congress delegated to EPA the decision whether and how to
    regulate carbon-dioxide emissions from [new, modified, and
    existing] powerplants” using the regulatory tools laid out in
    Section 7411. 
    564 U.S. at
    424–426.
    That is no doubt a significant task for the EPA. But that is
    not because of any agency overreach. It is the product of
    80
    Congress’ charge that the EPA regulate air pollution
    nationwide. And with respect to regulating greenhouse gas
    pollution in particular, it reflects the fact that fossil-fuel-fired
    power plants predominate the power industry and are spread
    across the Nation. See United States Energy Information
    Administration (EIA), Frequently Asked Questions: What is
    U.S. Electricity Generation by Source? (Nov. 2, 2020),
    https://www.eia.gov/tools/faqs/faq.php?id=427&t=2               (last
    visited Jan. 11, 2021); EIA, U.S. Energy Mapping System,
    https://www.eia.gov/state/maps.php (last visited Jan. 11,
    2021). So much so that they “are by far” the greatest stationary
    contributor to greenhouse gas pollution and the significant
    dangers it causes for the public health and welfare. New
    Source Rule, 80 Fed. Reg. at 64,522.
    2. Best System of Emission Reduction
    So what the EPA may regulate (greenhouse gas pollution),
    and whom it may target (power plants), and how (under Section
    7411) have all been resolved and so do not trigger the major
    questions doctrine.
    That leaves the EPA no place to house its major-question
    objection other than in the interpretation of the statutory term
    “best system of emission reduction,” 
    42 U.S.C. § 7411
    (a)(1).
    More specifically, the EPA says the use of any emission-
    control measures that do not operate at the individual physical
    plant level requires an express statement from Congress, and
    that federal standards that might encourage generation-shifting
    are therefore categorically forbidden under Section 7411.
    But the major questions doctrine does not apply there
    either for a number of reasons.
    81
    a. Statutory Design
    For starters, the “best system of emission reduction” plays
    a cabined role in the statutory scheme. The determination of
    the best system of emission reduction is entirely internal to the
    EPA.       The EPA itself evaluates relevant scientific,
    technological, and economic evidence to identify, in its
    judgment, the “best system of emission reduction” available,
    and the “degree of emission limitation achievable” through it.
    
    42 U.S.C. § 7411
    (a)(1).
    In making that determination, the statute significantly
    reins in the EPA’s judgment by requiring the Agency to
    (1) “tak[e] into account the cost of achieving such reduction,”
    (2) factor in “any nonair quality health and environmental
    impact,” (3) balance the effect on “energy requirements,” and
    (4) ensure that the system has been “adequately
    demonstrated[.]” 
    42 U.S.C. § 7411
    (a)(1). To be “adequately
    demonstrated[,]” we have explained, the system must be shown
    to be reasonably “reliable,” “efficient,” and “expected to serve
    the interests of pollution control without becoming exorbitantly
    costly[.]” Essex Chem. Corp. v. Ruckelshaus, 
    486 F.2d 427
    ,
    433 (D.C. Cir. 1973), cert. denied, 
    416 U.S. 969
     (1974); see
    also Portland Cement Ass’n v. Ruckelshaus, 
    486 F.2d 375
    , 391
    (D.C. Cir. 1973) (whether a system is adequately demonstrated
    “cannot be based on ‘crystal ball’ inquiry”).9
    9
    In addition to these statutory constraints, the EPA has tied its
    own hands by requiring that the best system include only actions
    touching three bases: (i) they reduce emissions (rather than, for
    example, capturing emissions after they are released into the air by
    planting trees), (ii) sources themselves can implement them, and
    (iii) they target supply-side activities. See Clean Power Plan, 80 Fed.
    Reg. at 64,776, 64,778–64,779.
    82
    Once the EPA identifies a best system that meets those
    requirements and calculates the degree of emission limitation
    it allows, the Clean Air Act leaves it to the States to set their
    own standards of performance for their existing pollution
    sources. 
    42 U.S.C. § 7411
    (d). The cooperative-federalism
    design of Section 7411(d) gives the States broad discretion in
    achieving those emission limitations. See AEP, 
    564 U.S. at 428
    (“The Act envisions extensive cooperation between federal and
    state authorities, generally permitting each State to take the first
    cut at determining how best to achieve EPA emissions
    standards within its domain[.]”) (internal citations omitted). In
    addition, Section 7411(d) expressly allows States, in setting
    their emission standards, to “take into consideration, among
    other factors, the remaining useful life” of its existing sources.
    
    42 U.S.C. § 7411
    (d).
    So the EPA’s scientific and technological identification of
    the best system of emission reduction cannot bear the major-
    question label. Determining the system is a task expressly and
    indisputably assigned by Congress to the EPA and requiring
    specialized agency expertise. That system serves only as the
    basis for the EPA to set the emission-reduction targets in its
    quantitative guidelines. The States retain the choice of how to
    meet those guidelines through standards of performance
    tailored to their various sources. Neither exercise entails
    resolution of a major question.
    The EPA argues that its own best-system process raised a
    major question by “impos[ing] ‘generation shifting[.]’” EPA
    Br. 99. But under Section 7411(d), the EPA does not impose
    the “best system of emission reduction” on anyone. Instead,
    each State decides for itself what measures to employ to meet
    the emission limits, and in so doing may elect to consider the
    “remaining useful life” of its plants and “other factors.” 
    42 U.S.C. § 7411
    (d). See Clean Power Plan, 80 Fed. Reg. at
    83
    64,709–64,710, 64,783. The Clean Power Plan, in fact,
    afforded States considerable flexibility in choosing how to
    calculate and meet their emissions targets. See, e.g., id. at
    64,665, 64,756–64,757, 64,834–64,837.10
    Congress already focused on the issue and made the
    decision to rope the EPA’s selection of a best system of
    emission reduction about with all of those substantive and
    structural limitations. So the major questions doctrine does not
    provide any basis for concluding that the Clean Air Act
    categorically forecloses the EPA’s consideration of even those
    generation-shifting measures that are already widely in use by
    States and power plants and have been demonstrated to be
    reasonable, reliable, effective, and not unduly disruptive to the
    regulated industry. See Clean Power Plan, 80 Fed. Reg. at
    64,735, 64,769.
    10
    The Clean Power Plan expressly contemplated that States and
    sources might choose to meet their emissions targets by using
    measures other than the specific heat-rate improvements and
    generation shifting that the EPA had identified in its best system. See
    80 Fed. Reg. at 64,755–64,758. The EPA offered a list of alternative
    available technologies that reduced power plants’ carbon dioxide
    emissions per megawatt, including carbon capture and storage, heat-
    rate improvements at non-coal plants, fuel switching to gas, fuel
    switching to biomass, and waste heat-to-energy conversion. Id. at
    64,756. In certain situations, for example, modifying coal-fired
    plants to burn natural gas could “help achieve emission limits
    consistent with the [best system].” Id. The Agency also identified a
    list of alternative measures that States could implement to lower
    overall emissions from fossil-fuel-fired plants. Those measures
    included, for example, demand-side energy efficiency—a policy tool
    that the EPA expected some States to use because “the potential
    emission reductions from demand-side [energy efficiency] rival
    those from [generation shifting] in magnitude[.]” Id.
    84
    In that respect, the EPA’s argument sounds much like a
    second argument rejected by the Supreme Court in UARG. In
    addition to the scope question discussed above, the Court
    addressed whether the EPA could require facilities that emit
    conventional pollutants also to implement the “best available
    control technology” for greenhouse gases. UARG, 573 U.S. at
    329–333 (citing 
    42 U.S.C. § 7475
    (a)(4)). Like the EPA here,
    the industry petitioners argued that the “best available control
    technology” standard was “fundamentally unsuited” to
    greenhouse gas emissions because it had “traditionally”
    focused on “end-of-stack controls.”           
    Id.
     at 329–330.
    “[A]pplying it to greenhouse gases,” the industry petitioners
    insisted, would make the “best available control technology”
    standard “more about regulating energy use, which will enable
    regulators to control every aspect of a facility’s operation and
    design[.]” 
    Id. at 330
     (internal quotation marks omitted).
    The Supreme Court rejected that challenge. The Court
    explained that the EPA’s guidance contemplated both “end-of-
    stack”–type controls and energy efficiency measures. UARG,
    573 U.S. at 330. And, critically, the Court emphasized that the
    statute and regulations already imposed “important limitations
    on [best available control technology] that may work to
    mitigate petitioners’ concerns about ‘unbounded’ regulatory
    authority.” Id. at 331. Among those limitations was the EPA’s
    longstanding statutory interpretation that the best available
    control technology was required “only for pollutants that the
    source itself emits,” and the EPA’s existing guidance that
    permitting authorities should “consider whether a proposed
    regulatory burden outweighs any reduction in emissions to be
    achieved.” Id. The statute also required the EPA to determine
    the best available control technology with reference to “energy,
    environmental, and economic impacts and other costs.” 
    42 U.S.C. § 7479
    (3); see also UARG, 573 U.S. at 333 n.9.
    85
    So too here: The numerous substantial and explicit
    constraints on the EPA’s selection of a best system of emission
    reduction foreclose using the major questions doctrine to write
    additional, extratextual, and inflexibly categorical limitations
    into a statute whose “broad language * * * reflects an
    intentional effort to confer the flexibility necessary to
    forestall * * * obsolescence.” Massachusetts v. EPA, 
    549 U.S. at 532
    ; see also Transmission Access Policy Study Group v.
    FERC, 
    225 F.3d 667
    , 711 (D.C. Cir. 2000) (where Congress
    has spoken, court upholds as within agency authority an order
    that “fundamentally change[d] the regulatory environment in
    which utilities operate” and “introduc[ed] meaningful
    competition into an industry that since its inception has been
    highly regulated and affecting all utilities in a similar way”),
    aff’d sub nom. New York v. FERC, 
    535 U.S. 1
     (2002).
    The EPA points to the Supreme Court’s statement in
    UARG that “[w]hen an agency claims to discover in a long-
    extant statute an unheralded power to regulate ‘a significant
    portion of the American economy,’ we typically greet its
    announcement with a measure of skepticism.” 573 U.S. at 324
    (quoting Brown & Williamson, 
    529 U.S. at 159
    ).
    True. But, as already explained, the EPA made no new
    discovery of regulatory power with the Clean Power Plan.
    While power plants are significant players in the American
    economy, they have been subject to regulation under Section
    7411 for nearly half a century. See, e.g., Costle, 
    657 F.2d at 318
    ; Oljato Chapter of Navajo Tribe v. Train, 
    515 F.2d 654
    ,
    656–57 (D.C. Cir. 1975). Their emission of massive amounts
    of carbon dioxide has long been known. And the source of the
    EPA’s duty to regulate that greenhouse gas pollution from
    power plants was the plain statutory text and Supreme Court
    precedent, not something the EPA pulled out of a hat. See AEP,
    
    564 U.S. at 425
    ; Massachusetts v. EPA, 
    549 U.S. at 532
    .
    86
    In sum, the Clean Air Act expressly confers regulatory
    authority on the EPA to set standards for reducing greenhouse
    gas emissions from fossil-fuel-fired power plants nationwide.
    Congress knew both the scope and importance of what it was
    doing. And it cabined the EPA’s authority with concrete and
    judicially enforceable statutory limitations.     The major
    questions doctrine is meant to discern, not override, such
    statutory judgments. Doubly so when the regulatory authority
    and its reach have been affirmed and enforced by the Supreme
    Court.
    b. Regulatory Consequences
    The problems with the EPA’s approach to the major-
    question analysis do not stop there. The Agency also conflates
    the significance of greenhouse gas regulation of power plants
    generally with any significance attributable solely to the EPA’s
    choice of a “best system of emission reduction”—the statutory
    provision where the EPA tried to anchor its major-question
    objection. Remember, the EPA concluded that the major
    questions doctrine was triggered centrally by (i) the Clean
    Power Plan’s “billions of dollars of impact” on the economy;
    (ii) its effect on “every electricity customer”; (iii) the number
    of litigation challenges it spawned, “involving almost every
    State”; and (iv) its perceived shifting of regulatory authority
    between federal agencies and the States. ACE Rule, 84 Fed.
    Reg. at 32,529.
    Taking the characterizations as true, those consequences
    are a product of the greenhouse gas problem, not of the best-
    system’s role in the solution. Given the number and dispersion
    of fossil-fuel-fired power plants, any nationwide regulation of
    their greenhouse gas pollution that meaningfully addresses
    emissions will necessarily affect a broad swath of the Nation’s
    electricity customers. Under the EPA’s grave endangerment
    87
    finding, so too would a failure to regulate those greenhouse gas
    emissions. See 2009 Endangerment Finding, 74 Fed. Reg. at
    66,496.
    As for the “billions of dollars of impact[,]” the EPA has
    offered no evidence tying that cost to generation shifting rather
    than physical plant adjustments or a variety of other means
    States might choose for complying with emission limits. As
    the EPA itself previously acknowledged, generation shifting
    can be cheaper than other demonstrated methods of reducing
    greenhouse gas emissions, like carbon capture and storage, that
    take place “at” the source (and thus fall within the EPA’s
    current statutory vision). See Clean Power Plan, 80 Fed. Reg.
    at 64,727.11 Moreover, the Clean Power Plan’s significant
    projected economic impact was not atypical for Clean Air Act
    rulemakings by the EPA. See, e.g., Costle, 
    657 F.2d at 314
    (upholding 1979 new source performance standards governing
    emission control by coal-burning power plants that imposed
    “tens of billions of dollars” of costs on the power sector).
    Even assuming that the EPA’s federalism concerns could
    trigger the major questions doctrine (rather than the federalism
    clear-statement canon), they carry no material weight here.
    That is because the statutory role of the best system of emission
    reduction under Section 7411(d) textually preserves and
    enforces the States’ independent role in choosing from among
    the broadest range of options to set standards of performance
    appropriate to sources within their jurisdiction. In fact, it is the
    11
    The EPA now takes the position that natural gas co-firing is
    not adequately demonstrated and that neither co-firing nor carbon
    capture and storage is part of the best system of emission reduction.
    See ACE Rule, 84 Fed. Reg. at 32,544–32,545, 32,549. But those
    methods are amenable to implementation “to” and “at” the source, in
    keeping with the EPA’s statutory view.
    88
    ACE Rule’s unreasoned barriers to certain compliance
    measures, like generation shifting and biomass co-firing, that
    hamstring the States. See supra Part II.A.3 (analyzing ACE
    Rule, 84 Fed. Reg. at 32,555–32,556).
    Finally, it seems doubtful that the volume of litigation
    aimed at a regulation can reasonably bear on its major-question
    status. The Supreme Court has certainly never embraced that
    idea. For good reason. A doctrine at the mercy of litigation
    stratagems, or the mere existence of disagreements over which
    parties find advantage in filing suit, cannot be an elucidating or
    even logically relevant tool of statutory interpretation.
    In any event, the EPA offers no basis for concluding that
    the best-system determination is what lit the litigation fire.
    After all, the ACE Rule too has been “subject to litigation”
    involving 43 States and all manner of other interested parties,
    despite the Rule’s jettisoning of generation shifting as part of
    the best system of emission reduction. See Opinion Caption,
    supra.
    c. Regulating in the Electricity Sector
    The ACE Rule’s last attempt to wrap the best-system
    determination in the major-question mantle asserts that
    including generation shifting as part of the best system of
    emission reduction lacks a “valid limiting principle,” and that,
    by “shifting focus to the entire grid[,]” it would “empower” the
    Agency “to order the wholesale restructuring of any industrial
    sector[.]” ACE Rule, 84 Fed. Reg. at 32,529. But that is
    entirely wrong. The Clean Power Plan was aimed not at
    regulating the grid, but squarely and solely at controlling air
    pollution—a task at the heart of the EPA’s mandate. Indeed,
    the EPA’s reasoning in the ACE Rule defeats its own
    argument.
    89
    The EPA suggests that counting generation shifting among
    the tools for emission reduction risks expanding the Agency’s
    regulatory sights too far, because “any action affecting a
    generator’s operating costs could impact its order of dispatch
    and lead to generation shifting.” ACE Rule, 84 Fed. Reg. at
    32,529 (emphasis added). That is exactly right: Any regulation
    of power plants—even the most conventional, at-the-source
    controls—may cause a relative increase in the cost of doing
    business for particular plants but not others, with some
    generation-shifting effect. That is how pollution regulation in
    the electricity sector has always worked. Regulators—
    including, for example, Congress in the Clean Air Act’s acid
    rain cap-and-trade program, 
    42 U.S.C. §§ 7651
    –7651o—have
    long facilitated those generation-shifting effects to serve the
    goal of pollution reduction. See Grid Experts Amicus Br. 13–
    15.
    So the EPA’s contention that it cannot consider measures
    resulting in generation shifting as part of its best system proves
    far too much: If that were so, the EPA would be limited to
    considering only measures that power plants could adopt at
    zero cost, so as to maintain their relative-dispatch position.
    That is, of course, incompatible with Congress’ instruction that
    the best system take cost into account as only one factor among
    several, see 
    42 U.S.C. § 7411
    (a)(1), and contrary to the very
    nature of environmental law, which requires the regulation of
    polluters and material changes in their pollution emissions.
    The EPA’s argument also ignores, again, the critical
    statutory limitations that the Clean Air Act imposes on the
    selection of a best system of emission reduction and its function
    in state plans. Under Section 7411(d), the EPA lacks the
    authority to “order the wholesale restructuring” of anything.
    All it can do is identify the best system of emission reduction
    that has been adequately demonstrated within the cost, energy-
    90
    requirement, and other substantive constraints set by Congress,
    and then calculate achievable emission goals by reference to
    that system. 
    42 U.S.C. § 7411
    (a)(1). States, in turn, set
    standards of performance only “for” any “existing source[,]”
    and need not implement any aspect of the EPA’s “best
    system[.]” 
    Id.
     § 7411(d)(1) (emphasis added). And the EPA’s
    determination about how best to combat air pollution is, of
    course, subject to judicial review, including on questions like
    whether a system has been adequately demonstrated and
    whether the Agency adequately considered costs. 
    42 U.S.C. § 7607
    (b); cf. AEP, 
    564 U.S. at 427
    ; UARG, 573 U.S. at 333
    n.9.     Congress’ carefully calibrated system—involving
    scientific and technological evidence-gathering, close study of
    existing industry practice, constrained discretion, divided
    regulatory authority, collaboration with States, and judicial
    review—leaves no room for the unauthorized agency
    overreach that the EPA fears.
    A group of States and industry groups intervened with
    other major-question challenges, but their salvos all fall short.
    They argue that the major questions doctrine is implicated
    because the EPA has “‘no expertise’ in electricity generation,
    transmission, and reliability.” State & Industry Intervenors
    Repeal Br. 30 (quoting King, 576 U.S. at 474); see also
    Gonzales, 
    546 U.S. at 267
     (rejecting interpretive rule of the
    Attorney General that was “both beyond his expertise and
    incongruous with the statutory purposes and design”). But
    Section 7411 not only foresees, but demands that the EPA
    consider “energy requirements” when assessing the best
    system of emission reduction. 
    42 U.S.C. § 7411
    (a)(1). The
    Supreme Court in AEP recognized the EPA’s signal role in
    regulating greenhouse gases under Section 7411
    notwithstanding that the EPA must consider energy
    requirements and ensure a reliable energy supply when it does
    so. 
    564 U.S. at 427
    . The Court explained that, when the EPA
    91
    is formulating greenhouse gas regulations, it must consider not
    only “the environmental benefit potentially achievable,” but
    also “our Nation’s energy needs and the possibility of
    economic disruption[.]” 
    Id.
     The Clean Air Act “entrusts such
    complex balancing to EPA in the first instance, in combination
    with state regulators.” Id.; see 
    42 U.S.C. § 7411
    (a)(1). That
    definitive reading of the statute by the Supreme Court cannot
    suddenly become a forbidden major question when the EPA
    regulates as it was told to do.
    The statutory scheme simply gives no quarter to the
    proposition that, in following Congress’ directive to regulate
    electricity-producing power plants, the EPA is categorically
    forbidden to consider emission-reduction measures that take
    into account the nature of the electricity grid in which those
    power plants operate day in and day out. Nor is it sensible to
    categorically put off-limits the generation-shifting measures
    that power plants are already actually using to meet emission
    requirements. See Clean Power Plan, 80 Fed. Reg. at 64,784–
    64,785.
    The State and Industry Intervenors also overlook that the
    EPA developed the Clean Power Plan with input from other
    agencies with relevant expertise. See Clean Power Plan, 80
    Fed. Reg. at 64,672–64,673 (explaining that “[i]nput and
    assistance from FERC [the Federal Energy Regulatory
    Commission] and DOE [the Department of Energy] have been
    particularly important in shaping” aspects of the Clean Power
    Plan); id. at 64,671 (noting “extensive consultation with key
    agencies responsible for [electric system] reliability[,]” as well
    as reliance on the “EPA’s longstanding principles in setting
    emission standards for the utility power sector”). Contrast
    Delaware Dep’t of Nat. Res. & Env’t Control v. EPA, 
    785 F.3d 1
    , 14, 18 (D.C. Cir. 2015) (invalidating rule in part because the
    EPA had failed to consult with other expert agencies on grid
    92
    reliability issues). EPA could hardly do its job without
    substantively engaging with the on-the-ground facts about the
    electricity system that power plants support. Quite the
    opposite: An agency’s wooden refusal to factor in reality and
    such on-point considerations would ordinarily render its
    decisionmaking arbitrary and capricious. See Motor Vehicle
    Mfrs. Ass’n v. State Farm Mut. Auto Ins. Co., 
    463 U.S. 29
    , 43
    (1983).
    All told, the EPA’s consideration of already-in-use
    generation shifting as part of the “best system of emission
    reduction” does nothing to enlarge the Agency’s regulatory
    domain. “We are not talking about extending EPA jurisdiction
    over millions of previously unregulated entities,” but about a
    familiar process of cooperative federalism applied to “entities
    already subject to * * * regulation” to address a recognized
    form of air pollution that repeatedly has been found to endanger
    public health and welfare. See UARG, 573 U.S. at 332. The
    major questions doctrine cannot rescue the ACE Rule’s
    mistaken interpretation of Section 7411(d) as categorically
    confining the best system of emission reduction to physical
    adjustments made only “at” and “to” the power plant.
    C. FEDERALISM
    The federalism canon lends no support to the ACE Rule’s
    decision to confine the best system of emission reduction to
    measures that apply exclusively at and to the source. That
    canon recognizes that “the States retain substantial sovereign
    powers under our constitutional scheme, powers with which
    Congress does not readily interfere.” Gregory v. Ashcroft, 
    501 U.S. 452
    , 460–461 (1991). So as a matter of constitutional
    avoidance, courts require Congress to “enact exceedingly clear
    language if it wishes to significantly alter the balance between
    federal and state power.” United States Forest Serv. v.
    93
    Cowpasture River Pres. Ass’n, 
    140 S. Ct. 1837
    , 1849–1850
    (2020).
    The federalism clear-statement rule prevents direct federal
    intrusion into areas of traditional state responsibility unless
    Congress has made its intent to cross that line explicit. For
    example, courts will not assume that Congress meant to
    preempt a State’s mandatory retirement age for state judges
    through the passage of a generic age discrimination law, unless
    it has clearly expressed its intent to police the qualifications of
    such high-level state officials. See Gregory, 
    501 U.S. at
    463–
    464. Nor will courts lightly assume that Congress intended to
    claim state-owned land as part of the National Park System, see
    Cowpasture River, 140 S. Ct. at 1849–1850, to transform
    simple state-law assaults into breaches of international
    chemical weapons compacts, see Bond v. United States, 
    572 U.S. 844
    , 862–863 (2014), or to displace the States’ traditional
    authority to regulate the practice of law, see American Bar
    Ass’n v. FTC, 
    430 F.3d 457
    , 466, 471–472 (D.C. Cir. 2005).
    Only when such conflicts between federal and state regulatory
    domains are plainly joined by Congress itself will the court
    confront the sensitive constitutional implications of such
    measures.
    That doctrine does not support the EPA’s cramped reading
    of Section 7411. Interstate air pollution is not an area of
    traditional state regulation. And federalism concerns do not bar
    the United States government from addressing areas of federal
    concern just because its actions have incidental effects on areas
    of state power. Cf. FERC v. Electric Power Supply Ass’n, 
    136 S. Ct. 760
    , 775–778 (2016) (federal regulation of wholesale
    electricity market did not intrude on traditional state authority
    over the retail electricity market, even though wholesale
    market regulation created an incentive for retail consumers to
    change their behavior in state-regulated markets).
    94
    What is more, the Supreme Court has suggested that the
    federalism clear-statement rule is of limited applicability when
    a federal regulatory regime is enforced through a statutory
    cooperative-federalism framework, as Section 7411(d) is. See
    AT&T Corp. v. Iowa Util. Board, 
    525 U.S. 366
    , 378 n.6 (1999)
    (noting appeals to States’ rights as “most peculiar” in the
    context of “a federal program administered by 50 independent
    state agencies”); see also Alaska Dep’t of Env’t Conservation
    v. EPA, 
    540 U.S. 461
     (2004) (declining to adopt dissent’s
    proposed clear-statement rule for federal constraints on state
    implementation decisions in cooperative-federalism program).
    See generally Abbe Gluck, Intrastatutory Federalism and
    Statutory Interpretation: State Implementation of Federal Law
    in Health Reform and Beyond, 121 YALE L.J. 534, 555–556
    (2011).
    In any case, the Clean Power Plan’s incorporation of
    generation shifting into its best system of emission reduction
    fell squarely within an area of the federal government’s
    constitutional competence. The EPA does not dispute the
    government’s authority or its statutory mandate to reduce the
    emission of pollutants that endanger public health and welfare.
    
    42 U.S.C. § 7411
    (b)(1)(A), (d)(1). The EPA also agrees that
    greenhouse gases are among the pollutants properly regulated
    by the federal government. See AEP, 
    564 U.S. at
    416–417,
    424; see also supra Part I.B.2.
    The Clean Power Plan directly regulated only the amount
    of greenhouse gas pollutants that may be emitted into the
    atmosphere. 80 Fed. Reg. at 64,663–64,664. That is an area
    of unique federal concern. After all, “[a]ir pollution is
    transient, heedless of state boundaries,” EME Homer City
    Generation, 572 U.S. at 496, particularly where the pollutants
    are greenhouse gases, which have little if any localized effect
    but great cumulative impact. The inability of individual States
    95
    to redress the problem of interstate air pollution, in fact, was
    among the very reasons for the enactment of the Clean Air Act.
    See 
    42 U.S.C. § 7401
    (a)(1), (4); S. REP. NO. 88-638, at 3 (1963)
    (“Polluted air is not contained in a specific area but is carried
    from one political jurisdiction to another. It does not know
    State lines or city limits. Providing air of good quality * * * is
    a challenge and an obligation for Government operations on all
    levels.”); 
    id. at 5
     (“The nationwide character of the air
    pollution problem requires an adequate Federal program to
    lend assistance, support, and stimulus to State and community
    programs.”).
    To be sure, the federal government’s regulation of such an
    interstate problem can have indirect effects on State energy
    production and utility regulation decisions. But even when
    those effects are the fully anticipated “natural consequences”
    of an agency’s policy choice, Electric Power Supply Ass’n, 
    136 S. Ct. at 776
    , that does not transform a fundamentally federal
    action in a core federal area of concern into a restriction on state
    action that triggers the federalism canon.12
    The EPA protests that the Clean Power Plan breached that
    divide because it expressly considered generation shifting to
    12
    In the ACE Rule, the EPA suggested that the Clean Power
    Plan’s best system of emission reduction was also impermissible as
    an encroachment on “measures and subjects exclusively left to
    FERC[.]” 84 Fed. Reg at 32,530. The EPA has not pressed that
    argument here. For good reason. The effects of environmental
    regulations on the power grid do not amount to power regulation
    statutorily reserved to FERC. And, in any event, the constitutional
    concerns that require us to patrol the boundaries between federal and
    state authority with vigilance do not support any similar clear-
    statement requirement regarding turf battles between federal
    agencies.
    96
    determine the best system of emission reduction and, in so
    doing, stepped on the States’ power to regulate electrical
    utilities’ mix of electricity generation. Reg.
    But that argument has nothing to do with the narrow
    construction of Section 7411 that the EPA adopted. After all,
    the EPA could have set the same emission guidelines
    predicated on a best system of emission reduction that
    exclusively employed technological controls applicable at and
    to the source, like carbon capture and sequestration. And the
    EPA must agree that the federalism canon would play no role
    in determining the appropriateness of that system, since on the
    Agency’s own reading, measures applicable at and to the
    source are precisely what Section 7411 allows.13
    Nowhere does the EPA explain why reference to a
    different mechanism—generation shifting—in its calculation
    of the best system would raise materially different federalism
    13
    While the EPA did not select carbon capture and sequestration
    as the best system of emission reduction in the ACE Rule, it excluded
    that process because of cost and feasibility concerns, not federalism
    interests. See 84 Fed. Reg. at 32,547–32,549. That exclusion was a
    change of position from the Clean Power Plan, where the EPA found
    that the process was “technically feasible and within price ranges that
    the EPA has found to be cost effective[.]” 80 Fed. Reg. at 64,727.
    Carbon capture and sequestration ultimately was not selected as the
    best system of emission reduction in the Clean Power Plan solely
    because generation shifting was even more cost-effective. Id. at
    64,727–64,728. What matters here is that the EPA did not express
    any concern in either the ACE Rule or the Clean Power Plan that
    such a system would intrude upon traditional areas of State authority.
    In the ACE Rule, the EPA permits the use of such technological
    controls to meet its emission standards, 84 Fed. Reg. at 32,549,
    32,555, as it did in the Clean Power Plan, 80 Fed. Reg. at 64,883–
    64,884.
    97
    concerns. Under either system, the only direct obligation
    imposed on States is the same: a federally set emissions
    guideline. In both scenarios, the States remain equally free to
    choose the compliance measures that best fit the needs of their
    State and industry. And as a practical matter, many if not most
    States would likely opt for generation shifting over carbon
    capture and sequestration under either rule because the former
    is cheaper for existing plants. See Clean Power Plan, 80 Fed.
    Reg. at 64,727–64,728; ACE Rule, 84 Fed. Reg. at 32,532
    (“Market-based forces have already led to significant
    generation shifting in the power sector.”).
    The EPA also suggests that the clear-statement rule
    operates with particular force here because the Plan imposed
    uneven regulatory burdens weighted toward States with more
    high-emitting power plants. But that argument tries to twist
    principles of federalism into a command of regulatory
    homogenization that defies on-the-ground reality. Regulations
    under the Clean Air Act or any environmental law will
    commonly affect States differently depending on the States’
    activities. The regulation of pollutants associated with
    automotive manufacturing affects States with production
    facilities more than those without. See, e.g., General Motors
    Corp. v. United States, 
    496 U.S. 530
    , 534–535 (1990). The
    regulation of mining-related pollutants imposes greater costs
    on States with more plentiful mineral resources. See, e.g.,
    Alaska Dep’t of Env’t Conservation, 
    540 U.S. at
    469–470, 474;
    Hodel v. Virginia Surface Mining & Reclamation Ass’n, 
    452 U.S. 264
    , 289–290 (1981). The same point applies to industries
    like petroleum refining, which are concentrated near navigable
    waters. See generally EIA, U.S. Energy Mapping System
    https://www.eia.gov/state/maps.php (last visited Jan. 11,
    2021). Indeed, some regulations impose additional regulatory
    burdens based literally on the direction the wind blows. See
    EME Homer City Generation, 572 U.S. at 520. Likewise,
    98
    States with more navigable water necessarily carry more
    burdens under the Clean Water Act than those with less.
    Affected States, of course, could raise statutory challenges
    to enforce the Clean Air Act’s express constraints, such as
    required consideration of cost, non-air quality health and
    environmental impact, or energy requirements under Section
    7411(a). And they could always challenge any unreasoned or
    unwarranted distinctions in regulatory coverage as arbitrary or
    capricious. But in the absence of such an objection, it does not
    offend—or even implicate—principles of federalism to
    observe that States whose industries pollute the Nation’s air
    and so harm the public’s health more will, in turn, be affected
    more by emission controls.
    For all of those reasons, nothing in the federalism canon
    supports the EPA’s effort to categorically constrict the best
    system of emission reduction to measures physically applied at
    and to the individual plant.
    III. THE EPA’ S AUTHORITY TO REGULATE
    CARBON DIOXIDE EMISSIONS UNDER SECTION 7411
    A. THE COAL PETITIONERS’ CHALLENGES
    The North American Coal Corporation and Westmoreland
    Mining Holdings LLC, both coal mine operators (the Coal
    Petitioners), bring two challenges to the ACE Rule. Both
    question the EPA’s legal authority to enact the rule. First, the
    Coal Petitioners argue that the EPA failed to make the required
    endangerment finding––that carbon dioxide emissions from
    power plants cause or contribute significantly to air pollution
    that may reasonably be anticipated to endanger public health or
    welfare––before regulating those emissions. See 
    42 U.S.C. § 7411
    (b)(1)(A). Second, they claim that the EPA’s previous
    regulation of a different air pollutant (mercury) from power
    99
    plants under the Hazardous Air Pollutants provision, 
    42 U.S.C. § 7412
    , precludes the EPA from now regulating power plants’
    emission of greenhouse gases under Section 7411(d).
    Both arguments fail. The EPA made the requisite
    endangerment finding in 2015, and the ACE Rule expressly
    retained that finding. As for the Section 7412 challenge, the
    EPA has correctly and consistently read the statute to allow the
    regulation both of a source’s emission of hazardous substances
    under Section 7412 and of other pollutants emitted by the same
    source under Section 7411(d). The Coal Petitioners’ argument
    rests not on the enacted statutory language, but instead on their
    own favored reading of one statutory amendment inserted by
    codifiers. Reading the statutory text as a whole—that is, all of
    the relevant language enacted by Congress, including two duly
    enacted amendments—the Clean Air Act authorizes the EPA
    to regulate both power plants’ emissions of greenhouse gases
    under Section 7411(d) and hazardous air pollutants under
    Section 7412. That reading is reinforced by the statutory
    structure, purpose, and history.
    1. Endangerment Finding
    a. The Record of Endangerment
    The Coal Petitioners argue that the ACE Rule was
    unlawful right out of the box because the EPA failed to make a
    statutorily required finding that greenhouse gas emissions from
    power plants cause air pollution that endangers the public
    health and welfare. That is wrong.
    As a reminder, before the EPA can regulate a category of
    stationary sources like electricity-generating power plants
    under Section 7411, the EPA Administrator must first find that
    the source category “in his judgment * * * causes, or
    contributes, significantly to, air pollution which may
    100
    reasonably be anticipated to endanger the public health or
    welfare.”      
    42 U.S.C. § 7411
    (b)(1)(A).          A formal
    pronouncement meeting those criteria is known as an
    “endangerment finding.” New Source Rule, 80 Fed. Reg. at
    64,529. And once it is made, the EPA is not just empowered,
    but obligated, to regulate. See 
    42 U.S.C. § 7411
    (b)(1)(A); see
    also supra note 8.
    After the Administrator makes an endangerment finding,
    the source category is added to the EPA’s Section 7411 list, 
    42 U.S.C. § 7411
    (b)(1)(A), and the Administrator must
    promulgate emissions standards (called “standards of
    performance”) for new sources in the category, 
    id.
    § 7411(b)(1)(B). As relevant here, unless those dangerous
    emissions are regulated under another relevant provision of the
    Clean Air Act, the Administrator must also set an achievable
    emission guideline based on the “best system of emission
    reduction” and provide a process for States to submit a plan
    setting out standards of performance for existing stationary
    sources in that same category. Id. § 7411(d)(1)(A)(ii).
    The EPA has for decades been regulating emissions other
    than carbon dioxide from electricity-generating power plants.
    In 1971, the EPA listed fossil-fuel-fired electricity-generating
    units with steam-generating boilers as a new source category
    under Section 7411(b) and promptly established standards of
    performance for them. See Air Pollution Prevention and
    Control: List of Categories of Stationary Sources, 
    36 Fed. Reg. 5931
     (March 31, 1971); Standards of Performance for New
    Stationary Sources, 
    36 Fed. Reg. 24,876
    , 24,878–24,880 (Dec.
    23, 1971). Then, in 1977, the EPA listed fossil-fuel-fired
    combustion turbines as a new source category under
    Section 7411 and set performance standards for them. See Air
    Pollution Prevention and Control: Addition to the List of
    Categories of Stationary Sources, 
    42 Fed. Reg. 53,657
     (Oct. 3,
    101
    1977); New Stationary Sources Performance Standards;
    Electric Utility Steam Generating Units, 
    44 Fed. Reg. 33,580
    (June 11, 1979). These categories cover the power plants at
    issue today. See New Source Rule, 80 Fed. Reg. at 64,531.
    Through the 2015 New Source Rule, the EPA began
    regulating carbon dioxide emissions from electricity-
    generating power plants. See New Source Rule, 
    80 Fed. Reg. 64,510
    . Because power plants had already been listed as a
    regulated source category, the New Source Rule did not need
    to take any action to add those plants to the Section 7411 list of
    regulated sources. It just issued, for the first time, standards of
    performance for carbon dioxide emitted from new power
    plants. In so doing, the New Source Rule provided the
    statutory predicate and corresponding duty for the EPA to
    establish carbon dioxide emission standards for existing power
    plants as well. Clean Power Plan, 80 Fed. Reg. at 64,715; see
    
    42 U.S.C. § 7411
    (d)(1). The New Source Rule now serves that
    same function for the ACE Rule, 84 Fed. Reg. at 32,533.
    Because the New Source Rule did not add a new category
    of pollution sources to the Section 7411 list, the EPA
    concluded that no new endangerment finding was needed.
    New Source Rule, 80 Fed. Reg. at 64,529–64,530. The EPA
    nevertheless went on to explain that it chose to regulate carbon
    dioxide emissions from electricity-generating plants
    specifically because greenhouse gas pollution endangers public
    health and welfare and contributes significantly to air pollution.
    See id. at 64,530–64,531. The EPA found in particular that
    increased atmospheric levels of greenhouse gases, including
    carbon dioxide, could lead to, among other things, more
    frequent extreme weather events and wildfires; threats to
    mental and physical health, especially for children and the
    elderly; reduced access to food and safe water; and mass
    102
    migrations and displacements as a result of rising sea levels.
    Id. at 64,517–64,520.
    b. Timeliness
    At the outset, the EPA argues that we must disregard the
    Coal Petitioners’ challenge concerning the endangerment
    finding because it was not timely filed. This is a close question,
    but we ultimately conclude that the petition is timely.
    The Clean Air Act requires that petitions for review
    challenging an EPA regulation––including any Section 7411
    standard of performance––generally must be filed within 60
    days of the regulation’s publication in the Federal Register. 
    42 U.S.C. § 7607
    (b)(1). The Clean Air Act’s timeliness bar is
    “jurisdictional in nature[.]” Motor & Equip. Mfrs. Ass’n v.
    Nichols, 
    142 F.3d 449
    , 460 (D.C. Cir. 1998) (quoting Edison
    Elec. Inst. v. EPA, 
    996 F.2d 326
    , 331 (D.C. Cir. 1993)).
    Importantly, Congress carved out an exception to that 60-
    day time limit if the petition “is based solely on grounds arising
    after [the] sixtieth day[.]” 
    42 U.S.C. § 7607
    (b)(1). In that
    situation, the clock resets, and the petitioner must file within 60
    days of the occurrence of the new event that “ripens [the]
    claim” and thereby triggers the basis for a challenge. Coalition
    for Responsible Regulation, Inc. v. EPA, 
    684 F.3d 102
    , 129
    (D.C. Cir. 2012), rev’d in part on other grounds sub nom.
    Utility Air Regulatory Group v. EPA (UARG), 
    573 U.S. 302
    (2014); see also Alon Refining Krotz Springs, Inc. v. EPA, 
    936 F.3d 628
    , 646 (D.C. Cir. 2019); Honeywell Int’l, Inc. v. EPA,
    
    705 F.3d 470
    , 472–473 (D.C. Cir. 2013); Sierra Club de Puerto
    Rico v. EPA, 
    815 F.3d 22
    , 26 (D.C. Cir. 2016). A claim
    “ripens” for purposes of the Clean Air Act when “subsequent
    factual or legal development creat[es] new legal consequences”
    for the party seeking review. Sierra Club de Puerto Rico, 815
    103
    F.3d at 28. This type of delayed challenge is commonly
    referred to as an “after arising” claim.
    We agree with the Coal Petitioners that the ACE Rule is
    an after-arising event that ripened their challenge to the New
    Source Rule’s endangerment finding.
    When the EPA promulgated the New Source Rule in 2015,
    the Coal Petitioners did not challenge that rule’s endangerment
    finding.14 That is because they did not plan “to build any new
    facilities affected by the New Source Rule,” and so were not
    directly affected by it. Coal Pet’rs Reply Br. 3. But when the
    ACE Rule used the New Source Rule as the predicate for
    regulating existing coal-fired power plants, ACE Rule, 84 Fed.
    Reg. at 32,533, the Coal Petitioners became concretely
    aggrieved by the finding.
    Under those circumstances, the Coal Petitioners’
    challenge to the New Source Rule as an insufficient predicate
    for the ACE Rule is timely. If the Coal Petitioners had filed
    suit when the New Source Rule was first promulgated in 2015,
    their standing would have been in doubt because they did not
    have any, or intend to build any, new power plants. An asserted
    injury arising from how the New Source Rule might come to
    14
    The Coal Petitioners claim that there is no timeliness problem
    because two trade associations with which the Coal Petitioners are
    affiliated––the National Mining Association and the United States
    Chamber of Commerce––challenged the New Source Rule. Coal
    Pet’rs Reply Br. 3 & n.2. There is no evidence or declaration
    regarding that relationship in the record, aside from counsel’s
    representation at oral argument. Oral Argument Tr. 131:13–17.
    Because we hold that the after-arising exception makes the Coal
    Petitioners’ own challenge timely, we do not address the relevance,
    if any, of a prior trade association challenge.
    104
    affect the regulation of their existing plants in the future might
    well have been too speculative to support judicial review. See
    Coalition for Responsible Regulation, 684 F.3d at 115–116,
    129–131 (challenge to preexisting regulations was timely,
    where regulations first affected petitioners due to the recent
    promulgation of rule targeting motor vehicle emissions); see
    also Sierra Club de Puerto Rico, 815 F.3d at 27; Honeywell,
    Int’l, 705 F.3d at 473. That is why “this court has assured
    petitioners with unripe claims that ‘they will not be foreclosed
    from judicial review when the appropriate time comes,’ * * *
    and that they ‘need not fear preclusion by reason of the 60-day
    stipulation barring judicial review,’” as long as they file a
    petition within 60 days of the injury that ripened their claim.
    Coalition for Responsible Regulation, 684 F.3d at 131
    (formatting modified).
    The EPA urges that the Coal Petitioners could have
    pressed a challenge to the New Source Rule in 2015 at the
    latest, as other coal-related entities did, once the EPA
    promulgated the Clean Power Plan in reliance on the New
    Source Rule’s endangerment finding. See North Dakota v.
    EPA, No. 15-1381 (and consolidated cases).
    Perhaps. See North American Coal Corp. v. EPA, No. 15-
    1451 (D.C. Cir.) (consolidated with West Virginia v. EPA, No.
    15-1363 (D.C. Cir.)). But that would argue over spilled milk.
    The Clean Power Plan litigation came to a halt when the EPA
    reconsidered that rule, and the case was ultimately dismissed
    as moot after the ACE Rule withdrew the Clean Power Plan.
    Per Curiam Order, West Virginia v. EPA, No. 15-1363 (D.C.
    Cir. Sept. 17, 2019), ECF No. 1806952. The Coal Petitioners
    have raised their claim in the ACE Rule litigation, and it would
    105
    seem perverse to say they instead should have litigated the
    matter in a case that will never be decided.15
    c. Adequacy of the Endangerment Finding
    On the merits, the Coal Petitioners press a two-fold
    challenge to the EPA’s compliance with the endangerment-
    finding requirement. First, they argue that Section 7411(b)
    requires the EPA to make a pollutant-specific endangerment
    finding for each stationary source category newly regulated
    under that provision. In their view, even though the EPA had
    already found that carbon dioxide emissions significantly cause
    or contribute to greenhouse gas air pollution that endanger the
    public health or welfare, the EPA also separately had to find
    that carbon dioxide specifically from coal-fired power plants is
    a significant source of that danger. 2009 Endangerment
    Finding, 74 Fed. Reg. at 66,499, 66,542 (for motor vehicles).
    Second, the Coal Petitioners claim that the EPA did not make
    such a finding, leaving it without authority to enact the ACE
    Rule.
    We need not address the Coal Petitioners’ first argument.
    Even assuming that Section 7411(b) requires a source-specific
    15
    There is a second exception to the timeliness bar known as
    the “reopening rule.” See, e.g., Environmental Def. v. EPA, 
    467 F.3d 1329
    , 1333 (D.C. Cir. 2006). The gist of that rule is that the 60-day
    jurisdictional review window restarts when an agency, either
    explicitly or implicitly, reconsiders its former action. See National
    Ass’n of Reversionary Prop. Owners v. Surface Transp. Bd., 
    158 F.3d 135
    , 141 (D.C. Cir. 1998); National Mining Ass’n v. United
    States Dep’t of Interior, 
    70 F.3d 1345
    , 1351 (D.C. Cir. 1995).
    Because the after-arising ripeness exception preserves the Coal
    Petitioners’ claim, we need not address the reopening doctrine.
    106
    endangerment finding for each pollutant, the EPA made a
    sufficient finding in the New Source Rule.
    i. The New Source Rule
    Before making the New Source Rule’s endangerment
    finding keyed to carbon dioxide from new fossil-fuel-fired
    power plants, the EPA explained its “rational basis” for
    regulating those sources’ emissions of that pollutant under
    Section 7411. New Source Rule, 80 Fed. Reg. at 64,530. The
    EPA first outlined why greenhouse gas emissions pose a
    danger to the public health and welfare, and then explained
    why it should regulate those emissions from power plants
    specifically.
    For evidence of the harms posed by greenhouse gas air
    pollution, the EPA first pointed to its 2009 Endangerment
    Finding, made in connection with the motor vehicle emissions
    regulation at issue in Coalition for Responsible Regulation.
    New Source Rule, 80 Fed. Reg. at 64,530. There, this court
    upheld as reasonable the EPA’s finding that greenhouse gas
    emissions threaten public health and welfare. Id.; see also
    Coalition for Responsible Regulation, 684 F.3d at 119–126.
    In the 2015 New Source Rule, the Agency reviewed
    substantial scientific evidence, including contemporary studies
    from the National Research Council, the Intergovernmental
    Panel on Climate Change, and others that post-dated the record
    from the 2009 motor vehicle emissions regulation. 80 Fed.
    Reg. at 64,530–64,531; see also id. at 64,517–64,520 (detailing
    updated developments in scientific evidence). The EPA found
    that the new studies “len[t] further credence to the validity of
    the [2009] Endangerment Finding.” Id. at 64,530. The EPA
    added that “[n]o information that commentators have presented
    or that the EPA has reviewed provides a basis for reaching a
    different conclusion,” and that the science at the time had
    107
    reaffirmed its understanding of the effects of greenhouse gases
    on the public health and welfare. Id. “The facts,” the EPA
    concluded, “unfortunately, have only grown stronger and the
    potential adverse consequences to public health and the
    environment more dire in the interim.” Id. at 64,531.
    The EPA next explained its reasons for regulating
    greenhouse gases from fossil-fuel-fired power plants
    specifically, pointing to the exceptionally high levels of
    emissions from those power plants. See New Source Rule, 80
    Fed. Reg. at 64,522–64,523, 64,530. To that end, the EPA
    found that fossil-fuel-fired power plants are the largest
    stationary sources of greenhouse gas emissions in the United
    States, accounting for nearly one-third of the United States’
    greenhouse gas emissions and as much as three times the
    emissions from the next ten categories of stationary sources
    combined. Id. at 64,530. Coal-fired power plants in particular,
    the EPA added, are the largest of those large emitters, with just
    one coal-fired power plant emitting potentially millions of tons
    of carbon dioxide annually. Id. at 64,531. In that way, power
    plant emissions “far exceed[ed] in magnitude the emissions
    from motor vehicles,” which had been the subject of the
    endangerment finding upheld in Coalition for Responsible
    Regulation. Id.
    ii. All Required Findings Were Made
    The Coal Petitioners acknowledge the EPA’s findings, but
    argue that Section 7411 requires a two-part endangerment
    finding––that carbon dioxide from fossil-fuel-fired power
    plants (1) endangers the public health and welfare, and
    (2) causes or contributes significantly to greenhouse gas air
    pollution. See 
    42 U.S.C. § 7411
    (b)(1)(A) (findings must be for
    the “category of sources”). The Coal Petitioners do not contest
    108
    that carbon dioxide endangers the public health and welfare.
    See Oral Argument Tr. 129:21–22.
    Instead, they train their arguments on the second prong,
    arguing that the New Source Rule did not properly make a
    finding that fossil-fuel-fired power plants “contribute[]
    significantly” to greenhouse gas pollution. First, they fault the
    EPA for relying on the New Source Rule, which provided a
    rational basis for regulation to support a significant-
    contribution finding.16 Second, they argue that the EPA
    arbitrarily and capriciously failed to define the threshold
    measure of a “significant” contribution.
    To survive those challenges, the EPA needed only to
    “articulate a satisfactory explanation” for the New Source
    Rule’s endangerment finding, making a “rational connection
    between the facts found and the choice made.” Motor Vehicle
    Mfrs. Ass’n v. State Farm Mut. Auto. Ins. Co. (State Farm), 
    463 U.S. 29
    , 43 (1983) (quoting Burlington Truck Lines v. United
    States, 
    371 U.S. 156
    , 168 (1962)). For an endangerment
    16
    The Coal Petitioners also argue that the EPA was wrong to
    rely on the 2009 Endangerment Finding because it used the lower
    “more than a de minimis or trivial” contribution standard. Coal
    Pet’rs Br. (quoting 2009 Endangerment Finding, 74 Fed. Reg.
    at 66,542). But the New Source Rule relies on the 2009
    Endangerment Finding only for part one of the endangerment finding
    test––that greenhouse gas pollution may reasonably be anticipated to
    endanger the public health and welfare––which the Coal Petitioners
    do not contest. See New Source Rule, 80 Fed. Reg. at 64,530–
    64,531. The EPA separately considered the volume of greenhouse
    gas emissions that motor vehicles contribute to the problem and
    found it significant. See 2009 Endangerment Finding, 74 Fed. Reg.
    at 66,499, 66,543; Coalition for Responsible Regulation, 684 F.3d at
    128.
    109
    finding, that choice need not include a “precise numerical
    value” that defines the threshold at which air pollution
    endangers the public health and welfare. Coalition for
    Responsible Regulation, 684 F.3d at 326. Instead, a “‘more
    qualitative’ approach,” employing reasoned predictions based
    on “empirical data and scientific evidence,” may suffice. Id. at
    327 (quoting Ethyl Corp. v. EPA, 
    541 F.2d 1
    , 56 (D.C. Cir.
    1976)). Such an approach “is a function of the precautionary
    thrust of the [Clean Air Act] and the multivariate and
    sometimes uncertain nature of climate science, not a sign of
    arbitrary or capricious decision-making.” 
    Id.
     By that measure,
    both of the Coal Petitioners’ objections fail.
    For starters, it is perfectly permissible, and commendably
    efficient, for an agency to re-confirm and build consistently
    upon such formally made factual determinations. It makes
    eminent sense, for example, for the EPA to take what it learned
    in regulating automobiles’ greenhouse gas emissions and apply
    that in evaluating the need for regulation of another source of
    the same pollutant––fossil-fuel-fired power plants. What
    matters here is that the EPA did not simply conclude that power
    plants’ greenhouse gas emissions significantly contribute to air
    pollution and stop there. Instead, the EPA went on to explain
    why that significant-contribution finding was warranted. See
    New Source Rule, 80 Fed. Reg. at 64,530–64,531 (explaining
    that power plants are the largest stationary sources of domestic
    greenhouse gas emissions and that each coal-fired plant may
    emit millions of tons of carbon dioxide per year).
    The Coal Petitioners’ argument that the EPA failed to
    articulate a specific threshold measurement for significance
    fares no better. While the failure to identify the trigger point
    for significance might prove problematic in cases at the
    margins, the EPA sensibly found that this one is not even close.
    Because of their substantial contribution of greenhouse gases,
    110
    “under any reasonable threshold or definition,” carbon dioxide
    from fossil-fuel-fired power plants represents “a significant
    contribution” to air pollution. New Source Rule, 80 Fed. Reg.
    at 64,531; cf. Massachusetts v. EPA, 
    549 U.S. at 525
     (While
    domestic automobile emissions accounted for less than one-
    third of the United States’ domestic emissions, “[j]udged by
    any standard, U.S. motor-vehicle emissions make a meaningful
    contribution to greenhouse gas concentrations and * * * to
    global warming.”).
    In that regard, we have already held that nothing in the
    Clean Air Act “require[s] that [the] EPA set a precise numerical
    value as part of” a contribution endangerment finding.
    Coalition for Responsible Regulation, 684 F.3d at 122
    (applying Section 7521(a)(1) of the Clean Air Act). So the
    “EPA need not establish a minimum threshold of risk or harm
    before determining whether an air pollutant endangers.” Id. at
    123.
    Nevertheless, the Coal Petitioners insist that, before
    finding significance, the EPA had to decide whether its inquiry
    would (1) address domestic or global emissions, (2) be
    measured by a “simple percentage criterion” or another metric,
    (3) factor in historical trends and/or future projections, and
    (4) involve a different process for greenhouse gases than other
    pollutants. See Coal Pet’rs Br. 17. Whether the EPA could
    reasonably decide to factor in such considerations is not before
    us. What matters here is that nothing in the Clean Air Act or
    precedent mandates determinations on each of those factors––
    at least not in a case in which there is no showing that any of
    them would have made any difference. Given that the United
    States, at the time of the endangerment finding, was the second-
    largest emitter of greenhouse gases in the world, see 2009
    Endangerment Finding, 74 Fed. Reg. at 66,538, it was not
    arbitrary or capricious for the EPA to conclude that the source
    111
    of close to one-third of those emissions is a significant
    contributor to air pollution by any measure. The global nature
    of the air pollution problem means that “[a] country or a source
    may be a large contributor, in comparison to other countries or
    sources, even though its percentage contribution may appear
    relatively small” in the context of total emissions worldwide.
    Id. Looking just at the Coal Petitioners’ calculations, power
    plants contributed a hefty 4.5 percent to global greenhouse gas
    emissions in 2013. See Coal Pet’rs Br. 18. More to the point,
    a holding that greenhouse gas emissions by fossil-fuel-fired
    power plants are not significant would make it nigh impossible
    for any source of greenhouse gas pollution to cross that
    statutory threshold.17
    For those reasons, we hold that the New Source Rule’s
    endangerment finding provided a sufficient basis for the EPA’s
    promulgation of the ACE Rule.
    2. Section 7411 and Section 7412’s Parallel Operation
    a. Background on the 1990 Amendments
    The Coal Petitioners next argue that the Clean Air Act
    expressly and unambiguously prohibits the EPA from
    17
    The EPA recently solicited public comment through a
    proposed rule on the appropriateness of considering such factors
    when making a significant-contribution finding. See Oil and Natural
    Gas Sector: Emission Standards for New, Reconstructed, and
    Modified Sources Review, 
    84 Fed. Reg. 50,244
    , 50,269 (Sept. 24,
    2019). But the EPA explained that the comments on the proposed
    rule are meant only “to inform the EPA’s actions in future rules,” 
    id. at 50,267
    , and explicitly declined to consider the merits of the
    comments or adopt any of the factors in that final rule, see Oil and
    Natural Gas Sector: Emission Standards for New, Reconstructed,
    112
    regulating coal-fired power plants’ carbon dioxide emissions
    under Section 7411(d) because those same power plants’
    mercury emissions are regulated under Section 7412’s
    Hazardous Air Pollutants provision. The relevant statutory text
    says otherwise.
    To set the stage, as relevant here, the Clean Air Act
    regulates pollutants emitted by stationary sources like power
    plants under three distinct programs: (1) the National Ambient
    Air Quality Standards (NAAQS) program that applies to
    emissions of six common air pollutants, 
    42 U.S.C. §§ 7408
    –
    7410; (2) the regulation of certain specified pollutants under
    the Hazardous Air Pollutants program, 
    42 U.S.C. § 7412
    ; and
    (3) the regulation of all other dangerous pollutants from new
    and existing sources under Section 7411.
    Congress designed the existing source provision in
    Section 7411(d) to ensure that there were “no gaps in control
    activities pertaining to stationary source emissions that pose
    any significant danger to public health or welfare.” S. REP.
    NO. 91-1196, at 20 (1970). So Section 7411(d), in its gap-
    filling capacity, covers all dangerous pollutants except those
    already regulated by NAAQS or the Hazardous Air Pollutants
    provision. See Clean Air Act Amendments of 1990 (“1990
    Amendments”), Pub. L. No. 101-549, § 108(g), § 302(a), 
    104 Stat. 2399
    , 2467, 2574.
    From the passage of the Clean Air Act until its amendment
    in 1990, Congress had left substantially to the EPA the task of
    building a program to effectively identify and regulate
    hazardous air pollutants under Section 7412. Specifically,
    Section 7412(b)(1)(A)––Section 112(b)(1)(A) of the 1970
    and Modified Sources Review, 
    84 Fed. Reg. 57,018
    , 57,058
    (Sept. 14, 2020).
    113
    Public Law––had instructed the EPA to publish a list of
    hazardous air pollutants that it would then regulate under
    Section 7412’s terms. See Clean Air Act Amendments of 1970
    (“1970 Amendments”), Pub. L. No. 91-604, sec. 4(a),
    § 112(b)(1)(A), 
    84 Stat. 1676
    , 1685. Section 7411(d), for its
    part, covered “any air pollutant * * * for which air quality
    criteria have not been issued or which is not included on a list
    published under section * * * 112(b)(1)(A)” by the EPA. 
    Id.,
    sec. 4(a), § 111(d)(1)(A), 84 Stat. at 1684.
    After two decades, Congress found that Section 7412 had
    “worked poorly” in that the EPA had regulated only eight
    hazardous pollutants under Section 7412. S. REP. NO. 102-228,
    at 128 (1989); see id. at 131. Through the 1990 Amendments
    to Section 7412, Congress forced the EPA’s hand by statutorily
    designating 191 hazardous pollutants that Congress required
    the EPA to regulate. See 1990 Amendments, sec. 301,
    § 112(b)(1), 104 Stat. at 2532–2535 (codified at 
    42 U.S.C. § 7412
    (b)(1)); see also S. REP. NO. 102-228, at 133. Congress
    also called on the EPA to add to the list. 1990 Amendments,
    sec. 301, § 112(b)(2)–(3), 104 Stat. at 2535–2537 (codified at
    
    42 U.S.C. § 7412
    (b)(2)–(3)). Neither greenhouse gases in
    general nor carbon dioxide in particular were on Congress’
    statutory list. Nor have they ever been added by the EPA.
    That change to Section 7412(b) necessitated a
    corresponding technical change to Section 7411(d)’s carve-out
    of pollutants already regulated under the Hazardous Air
    Pollutants program, since the cross-referenced “list published
    under section * * * 112(b)(1)(A)” no longer existed. Congress’
    update of the statutory cross-reference is the root of the present
    dispute. That is because each chamber of Congress articulated
    114
    the technical correction differently, and yet both were enacted
    into law.
    The Senate––in a section entitled “Conforming
    Amendments”––passed a straightforward amendment that
    struck “112(b)(1)(A)” from the Section 7411(d) exclusion, and
    replaced it with “112(b)”—which is the provision containing
    the new statutory list of hazardous pollutants to which the EPA
    could later add. 1990 Amendments, § 302(a), 104 Stat.
    at 2574. Just as before the 1990 Amendments, under the
    Senate Amendment, only hazardous pollutants on the
    Section 7412 list were excluded from Section 7411(d)’s
    regulation of existing sources’ emissions, while dangerous
    pollutants not addressed by the Hazardous Air Pollutants or
    NAAQS programs remained in Section 7411(d)’s domain.
    The House, for its part, called its technical amendment of
    the cross-reference “Miscellaneous Guidance,” and it similarly
    deleted “112(a)(1)(B)[,]” and then excluded any air pollutant
    that is “emitted from a source category which is regulated
    under section 112.” 1990 Amendments, § 108, 108(g), 104
    Stat. at 2465, 2467.
    Both of those amendments made it into the Conference
    Report, H.R. REP. NO. 101-952, at 73, 183 (1990) (Conf. Rep.),
    and, after being passed by both chambers of Congress and
    signed by the President, they both became part of the Public
    Law.
    Congress’ Office of the Legal Revision Counsel is tasked
    with compiling and codifying the public law and publishing it
    in the United States Code. The Counsel, of course, has no
    authority to alter the substance of the Statutes at Large. See
    Ganem v. Heckler, 
    746 F.2d 844
    , 851 (D.C. Cir. 1984) (“[T]he
    changes made by the codifiers, whose ‘choice, made * * *
    without approval of Congress * * * should be given no weight,’
    115
    are of no substantive moment.”) (internal quotation marks
    omitted) (quoting North Dakota v. United States, 
    460 U.S. 300
    ,
    310 n.13 (1983)); see also Positive Law Codification, OFFICE
    OF THE LAW REVISION COUNSEL, https://uscode.house.gov/
    codification/legislation.shtml (last visited Jan. 11, 2021) (For
    non-positive law titles, such as Title 42, “there are certain
    technical, although non-substantive, changes made to the text
    for purposes of inclusion in the Code.”).
    When faced with the Senate and House Amendments’
    differing articulations of the cross-reference update, the
    Counsel chose to publish only the House Amendment in the
    United States Code.
    b. Interpreting the House and Senate Amendments
    The Coal Petitioners argue that the House Amendment’s
    technical update of the cross-reference actually worked a major
    substantive change in the law by categorically and
    unambiguously excluding from Section 7411 not the hazardous
    pollutants already regulated under Section 7412, but any
    stationary sources of hazardous pollutants regulated under
    Section 7412. In their view, once a source is subject to
    regulation under Section 7412 for any single listed hazardous
    pollutant, all of its other pollution emissions are off limits for
    regulation under Section 7411(d). More specifically, the Coal
    Petitioners’ position is that, because the EPA regulates one
    hazardous air pollutant––mercury––emitted from coal-fired
    power plants, the EPA is powerless to regulate under
    Section 7411(d) every other non-“hazardous,” but still
    116
    significantly dangerous, pollutant those same power plants
    emit, including greenhouse gases.18
    On the other hand, for thirty years—from the enactment of
    the 1990 Amendments to the present day—the EPA has read
    the House’s “Miscellaneous Guidance” as just that—a
    miscellaneous technical amendment that, like the Senate
    Amendment, simply updated the Section 7411(d) cross-
    reference to exclude the regulation of a stationary source’s
    emission of pollutants that are already regulated under
    Section 7412.
    For the Coal Petitioners’ challenge to succeed, we would
    have to agree with their ambitious reading of the House
    Amendment as precluding regulation under Section 7411 of
    even those pollutants that are not covered by Section 7412. We
    also would have to ignore the duly enacted Senate Amendment
    entirely. And we would have to reject out of hand the EPA’s
    three-decade-old harmonizing reading of the statutory
    amendments, the text of Section 7411(d), and the statutory
    structure. We decline the invitation because that is not how
    statutory interpretation works.
    At the outset, the EPA seeks deference under Chevron
    U.S.A. Inc. v. Natural Resources Defense Council, Inc., 
    467 U.S. 837
     (1984). If this were an ordinary EPA interpretation
    of a Clean Air Act provision, we would apply exactly that
    framework. See UARG, 573 U.S. at 315 (“We review EPA’s
    18
    See National Emission Standards for Hazardous Air
    Pollutants from Coal- and Oil-Fired Electric Utility Steam
    Generating Units, 
    77 Fed. Reg. 9304
     (Feb. 16, 2012) (regulating
    mercury).
    117
    interpretations of the Clean Air Act using the standard set forth
    in Chevron[.]”).
    But this is no ordinary case. Here, the way in which the
    codifiers assembled the U.S. Code version of Section 7411(d)
    by omitting the Senate Amendment conflicts with the Statutes
    at Large, which is the definitive legal evidence of what the law
    is. 
    1 U.S.C. § 112
    ; see 
    id.
     § 204(a) (United States Code
    provides only prima facie evidence of the federal law). So any
    ambiguity arises from our duty to textually harmonize two duly
    enacted but differently articulated statutory provisions. In
    undertaking that task, we need not decide whether Chevron
    supplies the appropriate framework for reconciling conflicting
    statutory provisions. Compare Scialabba v. Cuellar de Osorio,
    
    573 U.S. 41
    , 64 (2014) (Kagan, J.) (plurality opinion), with 
    id. at 76
     (Roberts, C.J.) (concurring in the judgment). Instead, we
    independently reach the same conclusion as the EPA,
    harmonizing the House and Senate Amendments by giving
    “full effect” to both. 
    Id. at 64
    .
    i. The Consistent Meaning of Both Amendments
    In reconciling the Senate and House Amendments, we start
    with what the mission of the amendments was. The plain
    purpose of each amendment was to update Section 7411(d)’s
    outdated cross-reference to a list created by the EPA under
    Section 7412(b)(1)(A), in light of Congress’ publication of its
    new statutory list under Section 7412(b). That is why the
    Senate labeled its provision a “[c]onforming [a]mendment,”
    and the House called its version “[m]iscellaneous [g]uidance.”
    See 1990 Amendments, § 302(a), 104 Stat. at 2574 (Senate
    Amendment); id. § 108(g), 104 Stat. at 2465, 2467 (House
    Amendment). Neither amendment was meant to work a major
    substantive change in the law.
    118
    The Senate took the most direct textual path to updating
    Section 7411(d)’s cross-reference. Using the Public Law
    section number for Section 7412 (that is, Section 112), the
    Senate Amendment simply substituted “section 112(b)” for the
    outdated reference to “section 112(b)(1)(A).” See 1990
    Amendments, § 302(a), 104 Stat. at 2574. That way, the Senate
    Amendment maintains the parallelism of the two exclusions in
    Section 7411(d) for already-regulated pollutants that are either
    “included on a list published under section 108(a) [NAAQS] or
    112(b) [the Hazardous Air Pollutants provision.]” Id. § 302(a),
    104 Stat. at 2574 (incorporating Senate Amendment into the
    preexisting 1970 text, see 1970 Amendments, sec. 4(a),
    § 111(d)(1)(A), 84 Stat. at 1684). Both exclusionary clauses
    continue, as they had before the 1990 Amendments, to refer
    directly to specific air pollutants listed for regulation under
    other statutory provisions, and so to prevent duplicate
    regulation of the same harmful emissions.
    The House Amendment was less efficient, but ended up in
    the same place. It substituted for “section 112(b)(1)(A)” the
    phrase an air pollutant that is “emitted from a source category
    which is regulated under section 112[.]” 1990 Amendments,
    § 108(g), 104 Stat. at 2467 (codified at 
    42 U.S.C. § 7411
    (d)(1)(A)(i)).     So, with the House Amendment’s
    phrasing, Section 7411(d)’s exclusion reads, as relevant here,
    that each State shall
    establish[] standards of performance for any existing
    source for any air pollutant (i) for which air quality
    criteria have not been issued or which is not included
    on a list published under section 7408(a) of this title
    [the NAAQS program] or emitted from a source
    category which is regulated under section 7412 of this
    title [the Hazardous Air Pollutant program] but (ii) to
    which a standard of performance under this section
    119
    would apply if such existing source were a new
    source[.]
    
    42 U.S.C. § 7411
    (d)(1)(A).
    Reading the House Amendment within Section 7411(d)(1)
    “in [its] context and with a view to [its] place in the overall
    statutory scheme” shows that the House Amendment, like the
    Senate Amendment, just updated the cross-reference to exclude
    pollutant emissions already regulated for stationary sources
    under the Hazardous Air Pollutant program. King v. Burwell,
    
    576 U.S. 473
    , 486 (2015) (quoting FDA v. Brown &
    Williamson Tobacco Corp., 
    529 U.S. 120
    , 132, 133 (2000)).
    First, the entire point of the text that follows (i)––that is,
    romanette one––is to modify the phrase “air pollutant.” “Air
    pollutant” is, in fact, the last antecedent to which all of the
    language in romanette one speaks. And grammatically, the
    last-antecedent rule means that a limiting phrase is generally
    read to “modify[] only the noun or phrase that it immediately
    follows.” Lockhart v. United States, 
    136 S. Ct. 958
    , 962 (2016)
    (quoting Barnhart v. Thomas, 
    540 U.S. 20
    , 26 (2003)). In other
    words, the whole point of romanette one, including the House
    Amendment language, is to define which “air pollutant[s]”
    cannot be regulated under Section 7411(d) because those same
    pollutants are already regulated under the NAAQS or
    Hazardous Air Pollutants programs.
    Second, reading the entirety of romanette one to modify
    “air pollutant” gives the updated cross-reference to
    Section 7412 full meaning.19 See UARG, 573 U.S. at 317 (The
    19
    Contrary to the separate opinion’s view, see Separate Op. 34,
    use of the term “source category” (rather than “list”) leaves open
    whether the EPA might regulate, in its Section 7411(d) gap-filling
    120
    phrase “any air pollutant” in Section 7411 must be given “a
    reasonable, context-appropriate meaning[.]”). The EPA has
    regulated over 140 source categories under Section 7412. EPA
    Br. 180. But it regulates only their emission of hazardous
    pollutants. In other words, Section 7412’s regulatory scheme
    operates not broadly on the source category, but only on its
    emissions of the specified air pollutants. So Section 7412 does
    not and cannot police a source category’s every emission, only
    its emission of “hazardous” air pollutants. That is why it is
    called the Hazardous Air Pollutants program, not the
    Hazardous Sources program. Reading Section 7411(d) as
    excluding only those air pollutants already governed by
    Section 7412’s emissions regulations maps exactly onto
    romanette one’s parallel exclusion of pollutants (not sources)
    already regulated under NAAQS.                See 
    42 U.S.C. § 7411
    (d)(1)(A)(i). And it fits with Section 7411’s gap-filling
    purpose, which is to capture those dangerous air pollutants not
    covered by NAAQS or the Hazardous Air Pollutants program.
    See S. REP. NO. 91-1196, at 20.
    Third, at the same time that Congress amended
    Section 7411(d), it also added a savings clause,
    capacity, the emission even of hazardous air pollutants listed under
    Section 7412 when emitted by sources that Section 7412 does not
    reach, but to which Section 7411 does apply, see 
    42 U.S.C. § 7412
    (c)(1), (3)–(6); see also Clean Power Plan, 80 Fed. Reg. at
    64,714–64,715 (stating that “both the House and Senate amendments
    should be read individually as having the same meaning in the
    context presented in this rule,” but that “it is reasonable to interpret
    the House amendment of the Section [7412] Exclusion as only
    excluding the regulation of [hazardous air pollutant] emissions under
    [Clean Air Act] section [7411(d)] and only when that source
    category is regulated under [Clean Air Act] section [7412.]”)
    (emphasis added).
    121
    Section 7412(d)(7), to the Hazardous Air Pollutants provision.
    That provision says that “[n]o emission standard or other
    requirement promulgated under this section shall be
    interpreted, construed, or applied to diminish or replace * * *
    applicable requirements established pursuant to section [7411],
    part C or D[.]” 1990 Amendments, sec. 301, § 112(d)(7), 104
    Stat. at 2540–2541 (codified at 
    42 U.S.C. § 7412
    (d)(7)). That
    language requires reading Section 7411(d)’s simultaneously
    enacted cross-reference to regulation under Section 7412
    narrowly      and    consistently    with    Section 7411(d)’s
    complementary role in the statutory scheme. It certainly does
    not allow courts to read the cross-reference as the major
    amputation of authority to regulate that the Coal Petitioners
    propose.
    ii. The House Amendment Is Not a Trojan Horse
    The Coal Petitioners and the separate opinion eschew
    reading the House and Senate updates of the cross-reference
    harmoniously. They prefer to pit the House Amendment
    against the Senate Amendment and espy in the former a major
    change in the law that—without a word of warning or
    explanation—would have significantly curtailed the regulation
    of air pollutants and broadly insulated stationary sources from
    regulatory oversight for their non-hazardous but still-
    dangerously polluting emissions.
    There is a litany of problems with that approach.
    For starters, recall that the House and Senate Amendments
    were meant to address an outdated statutory cross-reference. It
    is not the function of a single chamber’s miscellaneous
    guidance or conforming amendment of a cross-reference to
    materially overhaul or truncate a statutory provision’s
    operative reach. Instead, reading both amendments together as
    serving the same purpose of cross-referencing a new statutory
    122
    list of air pollutants fits with their legislative purpose and text.
    To be sure, the Clean Air Act “is far from a chef d’oeuvre of
    legislative draftsmanship,” but “we, and EPA, must do our
    best, bearing in mind the ‘fundamental canon of statutory
    construction that the words of a statute must be read in their
    context and with a view to their place in the overall statutory
    scheme.’” UARG, 573 U.S. at 320 (quoting Brown &
    Williamson, 
    529 U.S. at 133
    ).
    More to the point, neither the House nor Senate
    Amendment said anything about changing the EPA’s
    affirmative regulatory obligation under Section 7411(d) to
    promulgate emissions guidelines for all air pollutants, except
    those already regulated under the NAAQS or Section 7412.
    Yet reading the House Amendment as abruptly withdrawing
    from Section 7411(d)’s reach entire source categories and all
    of the otherwise-unregulated emissions they spew would put
    the House Amendment in direct conflict with not only the
    unambiguous language of the Senate Amendment, but also
    with the Clean Air Act’s gap-filling structure and purpose, as
    well as with EPA’s overarching regulatory obligation. And it
    would supposedly do all of that contrary to the statutory
    history, in defiance of the technical and updating nature of the
    two Amendments, and without a whisper of warning by a
    single House or Senate member that the miscellaneous
    guidance would cripple Section 7411’s correlative function in
    the statutory scheme.
    At best, the Coal Petitioners’ and separate opinion’s vision
    of the House Amendment would have the EPA’s regulatory
    authority under Section 7411(d) turn on a fluke of timing. The
    Section 7412(d)(7) savings clause mentioned above, by its
    terms, protects the operation of Section 7411 regulations
    already in effect. So, too, does the House Amendment, which
    only excises what already “is regulated” under Section 7412.
    123
    Under the Coal Petitioners’ approach, then, the Clean Air Act
    would allow the EPA to regulate sources under both
    Section 7411(d) and Section 7412 if, and only if, the EPA
    adopted its Section 7411(d) regulation before the Section 7412
    regulation. No rational explanation is offered as to why
    Congress would want the mere sequencing of regulations to
    render them either lawful or invalid.
    More to the point, the Coal Petitioners and the separate
    opinion point to nothing in the legislative record even hinting
    at a rationale for removing Section 7412 sources entirely from
    Section 7411’s reach.      Nothing suggests that Congress
    intended to veer off in that substantive legislative direction.
    The Senate certainly had no such intention.
    The Coal Petitioners suggest that the EPA could instead
    regulate carbon dioxide under Section 7412. But they do not
    really mean it, as they say in the same breath that carbon
    dioxide would be a “poor fit” for Section 7412. Coal Pet’rs
    Br. 33 n.8. That is because Section 7412 strictly regulates all
    sources that emit ten tons per year or more of hazardous
    pollutants. 
    42 U.S.C. § 7412
    (a)(1). Adding carbon dioxide to
    that list would lead to a massive regulatory expansion of EPA
    authority to include everything from schools to hospitals and
    apartment buildings. Cf. UARG, 573 U.S. at 328. It would
    make no sense to conclude that Congress intended an
    unheralded string of words in a “Miscellaneous Guidance”
    amendment to hobble the gap-filling function of
    Section 7411(d) and to disable the EPA from addressing the
    source of one-third of this country’s greenhouse gas emissions.
    Nor can the Coal Petitioners hang their hats on the
    inclusion of the House Amendment in the codified version of
    Section 7411(d). Putting aside that the two amendments
    readily can, and so must, be read harmoniously as just updating
    124
    the exclusion of already-regulated air pollutants, it is settled
    that “the Code cannot prevail over the Statutes at Large when
    the two are inconsistent.” Stephan v. United States, 
    319 U.S. 423
    , 426 (1943); see also Five Flags Pipe Line Co. v.
    Department of Transp., 
    854 F.2d 1438
    , 1440 (D.C. Cir. 1988)
    (“[W]here the language of the Statutes at Large conflicts with
    the language in the United States Code that has not been
    enacted into positive law, the language of the Statutes at Large
    controls.”).
    The Coal Petitioners’ and the separate opinion’s other
    efforts to cast aside the Senate Amendment all fail.
    First, the Coal Petitioners and the separate opinion point to
    the Chafee-Baucus Statement of Senate Managers, in which
    Senators Chafee and Baucus addressed the negotiations
    surrounding the “Miscellaneous Guidance” in the 1990
    Amendments. Using this statement, the Coal Petitioners and
    the separate opinion try to brush off the duly enacted Senate
    Amendment as a scrivener’s or drafter’s error. To that end,
    they stress the Managers’ statement that, in the “Conference
    agreement,” the “Senate recedes to the House except * * * with
    respect to the requirement regarding judicial review of reports
    * * * and with respect to transportation planning[.]” 136
    CONG. REC. 36,007, 36,067 (Oct. 27, 1990).
    That argument does not even get out of the starting gate.
    It should go without saying that two Managers’ description of
    what a report said does not override the Conference Report
    itself. And it surely cannot erase the Senate Amendment text
    that was enacted by both the House and the Senate, and signed
    into law by the President.
    In fact, the Managers were wrong about what the
    Conference Report said. What the Conference Report actually
    says is that “the Senate recede[s] from its disagreement to the
    125
    amendment of the House to the text of the bill and agree to the
    same with an amendment as follows.” H.R. REP. NO. 101-952,
    at 1 (Conf. Rep.) (emphasis added). The “amendment [that]
    follow[ed]” included the text of the Senate Amendment as well
    as the House Amendment. See id. at 73, 183. So the agreement
    retained the Senate Amendment language; the Senate plainly
    did not withdraw it. The accompanying joint explanatory
    statement of the Conference Committee confirms that the
    Senate receded to the House subject to this amendment, “which
    [was] a substitute for the Senate bill and the House
    amendment” and contained both the House and Senate
    Amendments at issue here. See id. at 335.
    Beyond that, the Chafee-Baucus statement cannot bear the
    weight the Coal Petitioners and the separate opinion need it to
    carry. At most, as a “statement of managers,” it purports to
    summarize the more than 800-page Conference Report. 136
    CONG. REC. at 36,065. We generally do not view such
    statements as persuasive evidence of congressional intent, let
    alone an excuse for unceremoniously discarding unambiguous
    statutory text as a “drafter’s error.” See Separate Op. at 25
    cf. Weyerhaeuser Co. v. Costle, 
    590 F.2d 1011
    , 1052 n.67
    (D.C. Cir. 1978). Not to mention that we have specifically
    ruled that this very same floor statement carries little weight.
    Environmental Def. Fund, Inc. v. EPA, 
    82 F.3d 451
    , 460 n.11
    (D.C. Cir. 1996). Simply put, the statement’s purpose was to
    explain the report, not to change the content of the law, to
    resolve substantive conflicts, or to effect sweeping change in
    the statute’s reach. See Glossary Term: Statement of
    Managers, U.S. SENATE, https://www.senate.gov/reference/
    glossary_term/statement_of_managers.htm         (last    visited
    Jan. 11, 2021).
    Second, the Coal Petitioners argue that we should
    disregard the Senate Amendment because it is a “[c]onforming
    126
    [a]mendment.” See 1990 Amendments, § 302, 104 Stat.
    at 2574. A conforming amendment can serve to harmonize
    statutory provisions, which is exactly what the Senate
    Amendment did by updating the cross-reference. See Burgess
    v. United States, 
    553 U.S. 124
    , 135 (2008).
    That does not mean that the statutory provision can be
    ignored. See Burgess, 
    553 U.S. at 135
    . The Senate
    Amendment’s careful maintenance of the status quo through a
    cross-reference update evidences a deliberate preservation of
    the prior regulatory scope of Section 7411.
    By the way, if labels were what matters, the House’s
    “Miscellaneous Guidance” provides no platform for the major
    legislative surgery on Section 7411 that the Coal Petitioners
    and the separate opinion envision.
    Third, the Coal Petitioners ask us to defer to the Office of
    the Law Revision Counsel’s decision to codify the House
    Amendment rather than the Senate Amendment. The separate
    opinion reasons as well that the Office of Law Revision
    Counsel is “the leading candidate” for deference. Separate Op.
    23.
    No such deference is due. While the Office of the Law
    Revision Counsel has expertise in the technical aspects of the
    codification process, it has no license, without Congress’
    approval, to change the substantive meaning of enacted law or
    to throw away an entire statutory provision. See Ganem, 
    746 F.2d at 851
    . That is why the Public Law prevails over the
    United States Code in case of conflict. See 
    1 U.S.C. § 112
    ;
    Stephan, 
    319 U.S. at 426
    ; United States v. Welden, 
    377 U.S. 95
    , 98 n.4 (1964).
    Fourth, the Coal Petitioners point to Congress’ drafting
    manuals, which suggest that a first-in-time amendment, such as
    127
    the House Amendment, supersedes a later-in-the-legislative-
    process amendment like the Senate Amendment. See U.S.
    SENATE, OFFICE OF LEGISLATIVE COUNSEL , LEGISLATIVE
    DRAFTING MANUAL (“SENATE MANUAL”) § 126(d) (1997) (“If,
    after a first amendment to a provision is made * * * , the
    provision is again amended, the assumption is that the earlier
    (preceding) amendments have been executed.”); U.S. HOUSE
    OF REPRESENTATIVES, OFFICE OF LEGISLATIVE COUNSEL,
    HOUSE LEGISLATIVE COUNSEL’S MANUAL ON DRAFTING
    STYLE (“HOUSE MANUAL”) § 332(d) (1995) (“The assumption
    is that the earlier (preceding) amendments have been
    executed.”).
    One problem is that the Coal Petitioners provide no
    evidence that those manuals or their provisions were in place
    at the time of the 1990 Amendments.
    A bigger problem is that it is doubtful that the cited manual
    provisions even apply in this scenario. These provisions are
    located in sections for “Cumulative Amendments,” in which an
    amended provision is added onto by later provisions. See
    SENATE MANUAL § 126(d); HOUSE MANUAL § 332(d). Both
    manuals suggest that language should be added to such a
    provision to “alert the reader” to the later amendments.
    SENATE MANUAL § 126(d); see also, e.g., HOUSE MANUAL
    § 332(d)(1) (suggesting the following language for a
    cumulative amendment: “Title XX is amended by adding after
    section 123 (as added by section 802 of this Act) the following
    new section:”). That alert did not happen here. The House
    Amendment in Section 108 includes no reference to the Senate
    Amendment in Section 302, and there is no evidence that
    Congress believed it was adopting contradictory amendments
    in the final law.
    128
    The biggest problem of all is that nothing in the manuals
    says that a later but duly enacted amendment that has been
    signed into law can be cast aside as meaningless. Nor would it
    make any sense to do so here, when Congress placed the Senate
    Amendment in the logical statutory position to update a cross-
    reference to Section 7412. That amendment is located in the
    Public Law title addressing Hazardous Air Pollutants and is the
    very first provision (in Section 302 of the Public Law) that
    follows the many changes to Section 7412’s Hazardous Air
    Pollutants program (in Section 301 of the Public Law). See
    1990 Amendments, title III, sec. 301, § 112, 104 Stat. at 2531;
    id. sec. § 302(s), 104 Stat. at 2574. The House Amendment, on
    the other hand, appears as “[m]iscellaneous [g]uidance” in the
    title of the Public Law pertaining to the NAAQS program, not
    the Hazardous Air Pollutants program. See 1990 Amendments,
    title I, § 108(g), 104 Stat. at 2467.
    Finally, the Coal Petitioners and the separate opinion insist
    that, by subsuming the Senate Amendment’s targeted focus
    within their much broader reading of the House Amendment,
    they are somehow giving effect to both. See Coal Pet’rs Br.
    29–30; Separate Op. 28–30. The separate opinion sees it as no
    different than if a father did not want to name a child after a
    president from Virginia, and a mother did not want to name the
    child after any president. There is no conflict there, as the
    separate opinion sees it, because the mother’s sweeping
    prohibition includes “every name excluded by the father (and
    then some).” Separate Op. 29–30.
    But, of course, it is the “and then some” that is the
    problem. By vastly overshooting the technical task of
    correcting a cross-reference, the separate opinion’s and Coal
    Petitioners’ proposed reading of the House Amendment is not
    “supplement[ing]” the Senate Amendment’s exclusion of
    duplicate regulation. Separate Op. 30. It is supplanting it by
    129
    destroying the Senate Amendment’s express preservation of
    Section 7411(d)’s pre-existing regulatory directive. To borrow
    the analogy, the separate opinion’s vision of parental harmony
    is likely to be entirely lost on the father whose heart was set on
    naming his child Abraham, Theodore, or Harry.
    The Coal Petitioners’ and separate opinion’s fundamental
    mistake in claiming to give effect to both Amendments is that
    the statute cannot mean both what the Senate Amendment says
    and what they think the House Amendment says:
    Section 7411(d) as amended in the 1990 Act cannot have
    simultaneously preserved and eliminated Section 7411(d)’s
    preexisting reach. As this case shows, the difference is quite
    material: It determines whether Section 7411(d) allows any
    regulation of power plants’ greenhouse gas emissions or not.
    Given that, it blinks reality to claim that absorbing the Senate
    Amendment into the House Amendment in the manner the
    Coal Petitioners and the separate opinion propose somehow
    retains the Senate Amendment’s independent effect. A mouse
    swallowed by a snake, while still present in some metaphysical
    way, hardly feels equally preserved.
    At bottom, when confronted with two competing and duly
    enacted statutory provisions, a court’s job is not to pick a
    winner and a loser. The judicial duty is to read statutory text
    as a harmonized whole, not to foment irreconcilability. See
    Bell Atl. Tel. Cos. v. FCC, 
    131 F.3d 1044
    , 1047 (D.C. Cir.
    1997) (“Where, as here, we are charged with understanding the
    relationship between two different provisions within the same
    statute, we must analyze the language of each to make sense of
    the whole.”).      Reading both amendments consistently
    “pursue[s] a middle course” that “vitiates neither provision but
    implements to the fullest extent possible the directives of
    each[.]” Citizens to Save Spencer Cnty. v. EPA, 
    600 F.2d 844
    ,
    871 (D.C. Cir. 1979). Said another way, the better and quite
    130
    natural reading of all of the relevant enacted statutory text,
    structure, context, purpose, and history is one that harmonizes
    the House and Senate Amendments, avoids determining that
    one chamber of Congress smuggled dramatic and unlikely
    changes to the Agency’s regulatory authority into the Act
    through miscellaneous “guidance,” and instead faithfully
    accomplishes the legislative adjustment needed to respond to
    the changes to Section 7412.
    iii. The Harmonized Reading Stands the Test of Time
    Reading the two provisions consistently as successfully
    performing their “conforming” and “miscellaneous” task of
    updating Section 7411(d)’s cross-reference to continue to
    exclude air pollutants already regulated under Section 7412
    also maps onto the EPA’s consistent interpretation of the
    statute. And that reading has stood the test of time, without
    congressional correction. The EPA first announced its
    interpretation of Section 7411(d) as excluding Section 7412’s
    hazardous pollutants, rather than source categories, in the
    immediate wake of the 1990 Amendments. See Standards of
    Performance for New Stationary Sources and Guidelines for
    Control of Existing Sources: Municipal Solid Waste Landfills,
    
    56 Fed. Reg. 24,468
    , 24,469 (May 30, 1991) (explaining that
    Section 7411(d) requires States to submit plans for standards
    of performance for pollutants that endanger the public health
    or welfare but are “not ‘hazardous’ within the meaning of
    section 112 of the CAA and [are] not controlled under
    sections 108 through 110 of the CAA”). The EPA has not
    deviated from that interpretation in the ensuing decades. Oral
    Argument Tr. 174:19–22. The EPA’s view also gives effect to
    Section 7411(d)’s gap-filling purpose, see S. REP. NO. 91-
    1196, at 20, by allowing it to continue to regulate dangerous
    pollutants that are not policed by Section 7412 or NAAQS.
    131
    The EPA’s interpretation also dovetails with the
    development of judicial precedent. The Supreme Court has
    specifically addressed Section 7411(d)’s regulation of carbon
    dioxide emissions from fossil-fuel-fired power plants. In
    American Electric Power Co. v. Connecticut (AEP), the
    Supreme Court held that the Clean Air Act foreclosed any
    federal common law right to challenge the regulation (or lack
    thereof) of carbon dioxide emissions from power plants. 
    564 U.S. 410
    , 424–425 (2011). In so ruling, the Supreme Court
    relied on the displacing force of Section 7411, and specifically
    Section 7411(d). 
    Id.
     In ruling that “the Clean Air Act and the
    EPA actions it authorizes displace any federal common-law
    right to seek abatement of carbon-dioxide emissions from
    fossil-fuel fired powerplants,” the Supreme Court pointed
    directly to the Section 7411 regulatory scheme, including,
    “most relevant here, § 7411(d).” Id. at 424. The Supreme
    Court even noted that the “EPA is currently engaged in a
    § 7411 rulemaking to set standards for greenhouse gas
    emissions from fossil-fuel fired powerplants.” Id. at 425. As
    the Supreme Court explained, Section 7411 “‘speaks directly’
    to emissions of carbon dioxide from * * * [power] plants.” Id.
    at 424.
    The Coal Petitioners and the separate opinion put all their
    eggs in a footnote in AEP that notes Section 7411(d)’s
    exclusions. The footnote states that the “EPA may not employ
    § 7411(d) if existing sources of the pollutant in question are
    regulated under the national ambient air quality standard
    program, §§ 7408–7410, or the ‘hazardous air pollutants’
    program, § 7412.” AEP, 
    564 U.S. at
    424 n.7. That footnote
    comports with the EPA’s harmonized reading of the House and
    Senate Amendments because it says that Section 7411(d) does
    not apply when “the pollutant in question” is already regulated
    under one of the other two programs. See EPA Br. 189
    (pointing out that the footnote’s “use of the phrase ‘of the
    132
    pollutant in question’ suggests that [the Court] understood the
    regulatory bar to be pollutant-specific, consistent with EPA’s
    interpretation”).
    The footnote could not mean otherwise. At the time of
    AEP, electricity-generating power plants as sources of different
    pollutants were already regulated under the NAAQS
    provisions. See, e.g., American Trucking Ass’ns, Inc. v. EPA,
    
    283 F.3d 355
    , 359 (D.C. Cir. 2002) (considering NAAQS for
    particulate matter and ozone). So if the footnote did anything
    more than generally flag a statutory exclusion for already-
    regulated emissions—if it instead embraced the Coal
    Petitioners’ and separate opinion’s claim that Section 7411(d)
    excludes sources, rather than already-regulated emissions—
    then the Court could not have ruled as it did. Specifically, it
    could not have relied on Section 7411(d) to hold that the Clean
    Air Act displaced the common law by “speak[ing] directly” to
    the EPA’s authority to regulate power plants’ emission of
    greenhouse gases. See AEP, 
    564 U.S. at 424
    . The footnote
    certainly did not purport to unravel the central rationale for
    AEP’s holding.
    ***
    For all of those reasons, we hold that Section 7411(d)
    allows the EPA to regulate carbon dioxide emissions from
    power plants, even though mercury emitted from those same
    power plants is regulated as a hazardous air pollutant under
    Section 7412.
    B. T HE ROBINSON PETITIONERS’ CHALLENGES
    Another group of petitioners—including the Texas Public
    Policy Foundation, the Competitive Enterprise Institute, and
    various businesses that petitioned jointly with a forest-services
    firm named Robinson Enterprises, Inc. (together, the Robinson
    133
    Petitioners)—challenge the ACE Rule as overstepping the
    EPA’s authority. The Robinson Petitioners are the only parties
    that claim that the ACE Rule impermissibly regulates carbon
    dioxide emissions using Section 7411 of the Clean Air Act
    rather than Sections 7408 through 7410, under which the EPA
    sets NAAQS. Our ability to consider that claim fails due to the
    Robinson Petitioners’ lack of standing.
    The Robinson Petitioners assert the organizational
    standing of the Texas Public Policy Foundation and the
    Competitive Enterprise Institute, both nonprofit, nonpartisan
    organizations. Because the Foundation and the Institute seek
    the same relief on the same claim, only one needs to
    demonstrate standing. See American Anti-Vivisection Soc’y v.
    United States Dep’t of Agric., 
    946 F.3d 615
    , 619–620 (D.C.
    Cir. 2020). The two organizations argue standing based on
    harm to their own activities; neither appears to be a
    membership organization, and they claim no associational, or
    representational, standing based on harm to members.
    To establish standing, an organization, like an individual,
    must show an actual or imminent injury in fact that is fairly
    traceable to the challenged action and likely to be redressed by
    a favorable decision. See Havens Realty Corp. v. Coleman, 
    455 U.S. 363
    , 378–379 (1982); see also American Anti-Vivisection
    Soc’y, 946 F.3d at 618. Because neither organization is directly
    subject to the challenged rule, their “standing is ‘substantially
    more difficult to establish[.]’” Public Citizen, Inc. v. National
    Highway Traffic Safety Admin., 
    489 F.3d 1279
    , 1289 (D.C. Cir.
    2007) (Kavanaugh, J.) (quoting Lujan v. Defenders of Wildlife,
    
    504 U.S. 555
    , 562 (1992)).
    Each organization proffers a distinct ground and theory of
    standing, so we analyze them in turn. The standing of both the
    Texas Public Policy Foundation and the Competitive
    134
    Enterprise Institute falters on the first factor, injury in fact, so
    we need not consider the remaining two factors.
    The Texas Public Policy Foundation states that its mission
    is to provide legal counseling and services on a broad swath of
    matters, including promoting “a balanced approach to
    environmental regulation” by providing “legal counseling,
    referral, and advocacy services to individuals and businesses
    injured by federal, state, or local government overreach[.]”
    Decl. of Greg Sindelar ¶¶ 5, 7 (“[Its] mission is to promote,
    defend, and ensure liberty, personal responsibility, property
    rights, criminal justice reform, greater educational
    opportunities for all, a balanced approach to environmental
    regulation, free speech, state’s rights under the 10th
    Amendment, energy sufficiency, and free enterprise[.]”). The
    Foundation’s attorneys litigate cases on a wide range of issues
    on behalf of clients and refer clients to private counsel when
    necessary. Id. ¶ 8. The Foundation claims that the challenged
    rule has “caused a drain on [its] resources because [it] has had
    to divert significant time, effort, and resources from [its]
    activities in the area of property rights and wetlands regulation,
    for example,” in order to represent clients “who are forced to
    deal with” the federal regulation of greenhouse gases. Id. ¶ 9.
    It is well established that injury to an organization’s
    advocacy activities does not establish standing. See, e.g.,
    Center for Law & Educ. v. Department of Educ., 
    396 F.3d 1152
    , 1162 n.4 (D.C. Cir. 2005) (citing Sierra Club v. Morton,
    
    405 U.S. 727
    , 739–740 (1972)). That is because “the
    expenditure of resources on advocacy is not a cognizable
    Article III injury.” Turlock Irrigation Dist. v. FERC, 
    786 F.3d 18
    , 24 (D.C. Cir. 2015). To hold otherwise “would eviscerate
    standing doctrine’s actual injury requirement” by permitting an
    interest group to generate its own standing merely by putting
    an issue in its lawyers’ crosshairs. 
    Id.
     (quoting Center for Law
    135
    & Educ., 
    396 F.3d at
    1162 n.4); see also National Taxpayers
    Union, Inc. v. United States, 
    68 F.3d 1428
    , 1434 (D.C. Cir.
    1995). The Texas Public Policy Foundation declares only that,
    since the EPA issued the ACE Rule, it has increased its legal
    counseling, referral, and advocacy on behalf of clients affected
    by the regulation of greenhouse gases rather than other clients.
    That is precisely the kind of injury to advocacy—and
    expenditure of resources on such efforts—that we have held
    does not amount to injury in fact.
    The Foundation does not show the kind of perceptible
    impairment to its mission that sufficed for standing in a case
    like American Anti-Vivisection Society. There, we found injury
    because the agency’s inaction—specifically, its failure to
    promulgate standards regarding the humane treatment of
    birds—deprived the organization of key information on which
    its public educational activities depended. See 946 F.3d at 619.
    That inaction compelled the organization to develop guidance
    for the public that otherwise would have been provided by the
    agency’s standards. Id. By contrast, the Foundation fails to
    allege impairment of any similarly “discrete programmatic
    concerns” aside from its non-cognizable advocacy activities.
    National Taxpayers Union, 
    68 F.3d at 1433
     (quoting American
    Legal Found. v. FCC, 
    808 F.2d 84
    , 92 (D.C. Cir. 1987)).
    The Foundation points to Abigail Alliance for Better
    Access to Developmental Drugs v. Eschenbach, 
    469 F.3d 129
    (D.C. Cir. 2006), in arguing that the cost associated with more
    legal counseling, referral, and advocacy services is a source of
    injury.     But the “counseling, referral, advocacy, and
    educational services” at issue in Abigail Alliance were medical
    services, not legal services, and they directly furthered the
    plaintiff’s mission of providing access to potentially life-saving
    medical drugs and treatments. See 
    id.
     at 132–133. The
    Foundation’s transplantation of Abigail Alliance’s words into
    136
    the context of legal representation and counseling cannot
    change the outcome: the costs of litigation are not a cognizable
    Article III organizational injury. See Turlock, 786 F.3d at 24.
    The Competitive Enterprise Institute claims a different
    injury, which also falls short: the risk that it will face higher
    electricity bills. The Institute works to counter “economic
    overregulation in areas ranging from technology and finance to
    energy and the environment,” Decl. of Kent Lassman ¶ 3, and
    avers that it relies on electricity to power its headquarters in
    Washington, D.C., id. ¶¶ 2, 4. It says that the Regulatory
    Impact Analysis for the ACE Rule shows that the Rule could
    increase its electricity costs. That analysis estimated a 0.0% to
    0.1% increase in average retail electricity prices nationwide
    attributable to the Rule between 2025 and 2035. See S.A. 220
    (projecting baseline prices, in cents per kilowatt-hour, of 10.49
    and 10.71 in 2025 and 2030, respectively, as compared to 10.50
    and 10.72 under the ACE Rule, and estimating no increase
    attributable to the ACE Rule by 2035).
    The Regulatory Impact Analysis that the Institute cites
    modeled one “illustrative policy scenario on retail electricity
    prices[,]” S.A. 220, and included the caveat that the estimates
    were based on “inadequate and incomplete information[,]”
    meaning that “costs could be lower[,]” S.A. 222. The analysis
    acknowledged that “the EPA has not analyzed or modeled a
    specific standard of performance,” and recognized that costs
    could vary depending on “how states might apply the [best
    system of emission reduction] taking account of source-
    specific factors in setting standards of performance, and how
    sources might comply with those standards.” S.A. 221–222. It
    also identified “several key areas of uncertainty related to the
    electric power sector[,]” including electricity demand, natural
    gas supply and demand, and longer-term planning by utilities.
    S.A. 222.
    137
    Even a small injury may suffice to support standing, see,
    e.g., Competitive Enter. Inst. v. FCC (CEI), 
    970 F.3d 372
    , 384
    (D.C. Cir. 2020), but it must be “concrete and particularized
    and actual or imminent, not conjectural or hypothetical,” 
    id. at 381
     (quoting Spokeo, Inc. v. Robins, 
    136 S. Ct. 1540
    , 1548
    (2016)). “Were all purely speculative increased risks deemed
    injurious, the entire requirement of actual or imminent injury
    would be rendered moot, because all hypothesized,
    nonimminent injuries could be dressed up as increased risk of
    future injury.” Public Citizen, 489 F.3d at 1294 (quoting
    Natural Res. Def. Council v. EPA, 
    464 F.3d 1
    , 6 (D.C. Cir.
    2006)).
    In recognition that standing must rest on a concrete injury
    that is at least imminent, “we have repeatedly held that litigants
    cannot establish an Article III injury based on the independent
    actions of some third party not before this court.” Turlock, 786
    F.3d at 25 (formatting modified) (quoting Florida Audubon
    Soc’y v. Bentsen, 
    94 F.3d 658
    , 670 (D.C. Cir. 1996) (en banc)).
    “This is because ‘predictions of future events (especially future
    actions taken by third parties)’ are too speculative to support a
    claim of standing.” 
    Id.
     (quoting United Transp. Union v. ICC,
    
    891 F.2d 908
    , 912 (D.C. Cir. 1989)).
    The remoteness and contingency of the prospect that the
    Competitive Enterprise Institute will in the future actually face
    even the tiny rate increase tentatively projected as possibly
    arising from the challenged ACE Rule renders its claimed
    injury speculative and thus defeats its standing. In particular,
    the effect the Institute anticipates on its future electricity rates
    depends on how third parties—such as electricity generators,
    electricity providers, public utility commissions, and state
    pollution control agencies—might react to the ACE Rule. See
    EPA Br. 192. It also turns on the nature of standards that States
    decide to set, and on the compliance choices of regulated
    138
    sources. 
    Id.
     It remains entirely unclear what standards States
    would develop in response to the “best system of emission
    reduction,” how and whether those standards would have any
    effect on the costs of generation and transmission of energy,
    and whether rates will be affected by any offsetting savings
    through state or federal support for different generation mixes.
    A theory that “stacks speculation upon hypothetical upon
    speculation * * * does not establish an ‘actual or imminent’
    injury.” Turlock, 786 F.3d at 24 (quoting New York Reg’l
    Interconnect, Inc. v. FERC, 
    634 F.3d 581
    , 587 (D.C. Cir.
    2011)); see Arpaio v. Obama, 
    797 F.3d 11
    , 20–23 (D.C. Cir.
    2015). In asking us to anticipate the future actions of various
    third parties that are not before us, the Institute does just that.
    At oral argument, the Competitive Enterprise Institute
    identified as its strongest support our decision in Competitive
    Enterprise Institute v. FCC. But the concrete and actual injury
    claimed there was traceable through “a relatively simple causal
    chain[,]” 970 F.3d at 383, unlike the harm asserted here, which
    is based on “inadequate and incomplete information[,]”
    S.A. 222, and dependent on third parties’ unpredictable
    responses to the ACE Rule. Critically, the plaintiffs there
    demonstrated that their internet prices in fact had increased
    since the agency took its challenged action. CEI, 970 F.3d at
    382–383. This record lacks any such evidence.
    Because neither the Texas Public Policy Foundation nor
    the Competitive Enterprise Institute shows injury in fact to
    support the Robinson Petitioners’ standing, we cannot address
    the merits of their NAAQS-related challenge to the ACE Rule.
    IV. AMENDMENTS TO THE IMPLEMENTING REGULATIONS
    When the EPA repealed the Clean Power Plan and
    finalized the ACE Rule, it also changed the longstanding
    implementing regulations generally applicable to emission
    139
    guidelines promulgated under Section 7411(d) of the Clean Air
    Act. See ACE Rule, 84 Fed. Reg. at 32,564–32,571. The
    Public Health and Environmental Organization Petitioners (the
    Public Health Petitioners) challenge the implementing
    regulations insofar as they adopt new timing requirements that
    substantially extend the preexisting schedules for state and
    federal actions and sources’ compliance under Section 7411(d).
    See 
    40 C.F.R. §§ 60
    .23a(a)(1), 60.27a(b), 60.27a(c), 60.24a(d);
    see also ACE Rule, 84 Fed. Reg. at 32,567. Because the
    challenged regulations lack reasoned support, they cannot
    stand.
    The new implementing regulations extend the time
    allowed for States to submit their plans, for the EPA to review
    those plans, for the Agency to promulgate federal plans where
    state plans fall short, and for legally enforceable consequences
    to attach to sources that are slow to comply. Those extended
    timeframes apply unless the EPA otherwise specifies with
    respect to particular emission guidelines. See ACE Rule, 84
    Fed. Reg. at 32,568. The Public Health Petitioners argue that
    the amendments are arbitrary and capricious because the
    Agency altogether failed to address the urgency of controlling
    harmful emissions—especially the greenhouse gas emissions
    accelerating climate change.
    At the threshold, the EPA asserts that the Public Health
    Petitioners forfeited any challenge to the amended
    implementing regulations, but we conclude the claim was
    preserved. The EPA contends that Petitioners “barely
    mention” this claim in their opening brief, EPA Br. 268–269
    (citing CTS Corp. v. EPA, 
    759 F.3d 52
    , 60 (D.C. Cir. 2014)),
    but it was adequately, if concisely, set forth, see Pub. Health &
    Env’t Orgs. Br. 11–13. The issue is neither particularly
    complex nor as momentous as others in the case; Petitioners
    nonetheless clearly stated and supported the claim with
    140
    citations to the record and sources of legal authority. 
    Id.
     That
    relatively abbreviated treatment suffices. See, e.g., Tribune Co.
    v. FCC, 
    133 F.3d 61
    , 69 n.8 (D.C. Cir. 1998) (noting one
    paragraph in a fifty-eight-page brief arguing that the agency’s
    action was arbitrary and capricious sufficed to preserve the
    claim).
    Petitioners’ joint comment on this amendment as the EPA
    proposed it in the rulemaking process, which Petitioners cite in
    their brief, provides more detail. See Pub. Health & Env’t
    Orgs. Br. 13 (citing Comments of Environmental and Public
    Health Organizations on Proposed Revisions to Emission
    Guideline Implementing Regulations 26–27, J.A. 973–974).
    The EPA well understands the nature of the claim, see EPA Br.
    268–269, and there is no indication the brevity of the
    discussion in Petitioners’ opening brief prejudiced the Agency
    at all. Cf. Avia Dynamics, Inc. v. Federal Aviation Admin., 
    641 F.3d 515
    , 521 (D.C. Cir. 2011) (forfeiture excused where
    federal agency was placed on notice of arguments by extensive
    substantive motion practice).
    On the merits, the EPA failed to justify substantially
    extending established compliance timeframes, including
    deadlines that it has had in place since 1975. See State Plans
    for the Control of Certain Pollutants from Existing Facilities,
    
    40 Fed. Reg. 53,340
    , 53,345, 53,346–53,348 (Nov. 17, 1975).
    Before we can sustain agency action as nonarbitrary under the
    APA, “the agency must * * * articulate a satisfactory
    explanation for its action including a ‘rational connection
    between the facts found and the choice made.’” Motor Vehicle
    Mfrs. Ass’n of U.S., Inc. v. State Farm Mut. Auto. Ins. Co., 
    463 U.S. 29
    , 43 (1983) (quoting Burlington Truck Lines v. United
    States, 
    371 U.S. 156
    , 168 (1962)). Petitioners’ comments took
    issue with the tepid justifications the Agency offered, but the
    heart of their challenge is the EPA’s complete failure to say
    141
    anything at all about the public health and welfare implications
    of the extended timeframes.
    The Agency principally relied on reviving an argument it
    had considered and rejected when it first adopted the schedule
    it now displaces: that timeframes for the regulation of existing
    sources under Section 7411(d) should necessarily mimic or
    exceed timeframes for adoption of National Ambient Air
    Quality Standards (NAAQS) under Section 7410 of the Clean
    Air Act. Compare ACE Rule, 84 Fed. Reg. at 32,568, with
    State Plans for the Control of Certain Pollutants from Existing
    Facilities, 40 Fed. Reg. at 53,345. Section 7411(d) calls for
    regulations that “establish a procedure similar to that provided
    by [S]ection 7410[,]” which, like Section 7411, requires States
    to submit plans for the EPA’s approval and, if those plans are
    either not submitted or fall short, requires the EPA to itself
    prescribe a plan. See 
    42 U.S.C. § 7410
    (a)(1), (c)(1); 
    id.
    § 7411(d)(1)–(2). The two sets of rules accordingly reflect
    generally similar state-federal interactions.
    But it is not evident that the statement that Section 7411(d)
    would use “a procedure similar” to that employed under
    Section 7410 even speaks to timing rules. As the Agency
    recognized when it promulgated the 1975 rule, faster
    compliance was appropriate under Section 7411(d) because
    plans under this provision are far simpler. They apply only to
    a single category of source, whereas state plans for NAAQS
    under Section 7410 cover multiple types of sources. See 40
    Fed. Reg. at 53,345 (commenting that “Section [7411](d) plans
    will be much less complex than the [state implementation
    plans]” required under Section 7410). The Public Health
    Petitioners’ comment on the 2018 proposed amendments to the
    implementing regulations explained that “a section [7410 state
    implementation plan] must ensure that ambient air
    concentrations of a given pollutant in the state will stay below
    142
    the EPA-designated standard.” J.A. 971. That goal is “far
    more complicated to both achieve and demonstrate” than
    limiting source emissions under Section 7411(d), because
    “meeting the ambient air quality standards involves air quality
    monitoring, complex modeling procedures, close attention to
    such factors as topography, wind patterns, cross-[border]
    transport of air pollution, and many other considerations.”
    J.A. 971. By the same token, Petitioners commented that the
    EPA failed to justify giving itself as much time to review the
    simpler Section 7411(d) plans as it has to review state plans
    under Section 7410. J.A. 971–972. The EPA failed to engage
    meaningfully with the different scale of the two types of plans,
    dismissing Petitioners’ comment with the conclusory assertion
    that Section 7411(d) plans “have their own complexities and
    realities that take time to address.” ACE Rule, 84 Fed. Reg. at
    32,568.
    The EPA’s proposed rule also relied on more general
    claims that the amended timelines are appropriate because of
    the amount of work involved in States’ plan development and
    in the EPA’s review of those plans. See Emission Guidelines
    for Greenhouse Gas Emissions from Existing Electric Utility
    Generating Units; Revisions to Emission Guideline
    Implementing Regulations; Revisions to New Source Review
    Program: Proposed Rule, 
    83 Fed. Reg. 44,746
    , 44,771 (Aug.
    31, 2018). In response, Petitioners commented that the EPA
    did not document any problems during the decades that the
    existing timelines had been in place. J.A. 972 (“If the agency
    is truly concerned that the timing provision[s] in the framework
    regulations are unworkable, it must provide actual evidence of
    this—which it has not done thus far—and must propose
    amended provisions that correspond to the actual workload
    involved in section [7411(d)] rulemakings[.]”). The Final Rule
    failed to fill that gap. See, e.g., ACE Rule, 84 Fed. Reg. at
    32,568. Indeed, the Agency at one point seemed to forget that
    143
    it even had a burden of justification under the APA, going so
    far as to suggest that the obligation was somehow on the
    commenters to show that the various actors do not need any
    additional time. Id.
    It might be a close call whether, viewed in isolation, the
    analogy to Section 7410 and the general claim of need for more
    processing time could supply the “rational connection” the
    APA requires. State Farm, 
    463 U.S. at 43
    . But we do not view
    those reasons in isolation.
    The EPA’s weak grounds for routinizing additional
    compliance delays in the amended implementing regulations
    are overwhelmed by its total disregard of the added
    environmental and public health damage likely to result from
    slowing down the entire Section 7411(d) regulatory process.
    “Normally, an agency rule would be arbitrary and capricious if
    the agency * * * entirely failed to consider an important aspect
    of the problem[.]” State Farm, 
    463 U.S. at 43
    . The extensions
    of implementation deadlines here give no consideration to the
    need for speed. Control of emissions from existing sources
    before they harm people and the environment is the central
    purpose of Section 7411(d) of the Clean Air Act. Yet when it
    deferred the compliance deadlines, the EPA did not even
    mention the need for prompt reduction of those emissions or
    the human and environmental costs of its substantial new delay.
    In their comments, Petitioners emphasized the gravity and
    urgency of impending harms from unlawfully uncontrolled
    emissions as a reason the EPA must retain the tighter
    timeframes in the existing rule, not promulgate a new rule to
    build in additional years of delay. See Comments of
    Environmental and Public Health Organizations on Proposed
    Revisions to Emission Guideline Implementing Regulations
    26–27, J.A. 973–974. They stressed in particular the broad and
    144
    longstanding scientific consensus on the role of carbon dioxide
    emissions in accelerating climate change, and insisted that
    “deep emission reductions are needed immediately” in order to
    avoid “the worst effects of climate change,” making time “of
    the utmost essence.” 
    Id.
     They explained how the timing
    amendments stymie effective control of carbon dioxide
    emissions:
    [T]he amendments in question would permit up to 60
    months to elapse between the time an EPA emission
    guideline is finalized and the time that affected
    sources must, at a minimum, begin reducing their
    emissions through enforceable increments of
    progress. Assuming EPA issues a final emission
    guideline for power plant [carbon dioxide] emissions
    in mid-2019, designated sources can be expected to
    start reducing emissions in mid-2024. * * * [T]he
    world has surpassed not only the 350 ppm threshold—
    that atmospheric concentration of [carbon dioxide]
    that is considered the maximum safe level—but the
    400 ppm threshold as well. If we are to avoid the
    worst effects of climate change, deep emission
    reductions are needed immediately: time is simply of
    the utmost essence. For EPA to inject even further
    delay into the process * * * flouts the agency’s Clean
    Air Act obligation to require emission reductions to
    prevent this endangerment to public health and
    welfare.
    Comments of Environmental and Public Health Organizations
    27, J.A. 974.
    Not all source categories or types of emissions subject to
    Section 7411(d) present problems of the magnitude and
    urgency of those posed by unregulated carbon dioxide
    145
    emissions from power plants.        But the Public Health
    Petitioners’ comments on the Agency’s proposed amendments
    to the implementing regulations squarely called on the EPA to
    explain how slowing the regulatory timeframe with respect to
    any covered emissions or source category might be justified
    and consistent with the Act’s objective. See Comments of
    Environmental and Public Health Organizations 23, J.A. 970.
    In response to Petitioners’ concrete objections, the final
    rule neither changed nor better justified the timing provisions.
    In fact, upon reading the rule’s explanation of the deadline
    extensions, one would have no idea that the EPA actually
    recognized that greenhouse gas pollution was causing a global
    climate crisis requiring urgent remediation. In finalizing the
    proposed extensions to key deadlines, the EPA tersely
    reiterated its stated interest in giving itself, States, and
    regulated parties more time to comply—despite no showing of
    need—and, contrary to its explanation of the rule it displaced,
    stated that it was important after all to align the timing of the
    Section 7411(d) state-plan process with the compliance
    schedule under Section 7410. See ACE Rule, 84 Fed. Reg. at
    32,564, 32,568.
    The EPA did not even hint at how or whether it determined
    that prolonging public exposure to ongoing harms from
    pollutants emitted by existing source categories could be
    justified consistent with the core objectives of the Clean Air
    Act. That failure is irrational, especially in the face of the
    EPA’s continued adherence to its 2015 finding of an urgent
    need to counteract the threats posed by unregulated carbon
    dioxide emissions from coal-fired power plants. The EPA
    made no mention whatsoever of the harms that Petitioners
    warned would result if the Agency slackened the pace of state
    and federal action to mitigate the harms Section 7411(d)
    targets. In relation to the timing amendments, pollution
    146
    control—whether in the context of carbon dioxide and the ACE
    Rule or air pollution more generally—was simply not on the
    EPA’s agenda. In short, Petitioners called the EPA’s attention
    to an important aspect of the regulatory problem, and the EPA
    looked away.
    The EPA offered what is at best a radically incomplete
    explanation for extending the compliance timeline. It offered
    undeveloped reasons of administrative convenience and
    regulatory symmetry, even as it ignored the environmental and
    public health effects of the Rule’s compliance slowdown. The
    EPA thus “failed to consider an important aspect of the
    problem,” State Farm, 
    463 U.S. at
    43—indeed, arguably the
    most important aspect.          We accordingly vacate the
    implementing regulations’ extensions of the Section 7411(d)
    compliance periods.
    V. VACATUR AND REMAND
    The ACE Rule expressly rests on the incorrect conclusion
    that the plain statutory text clearly foreclosed the Clean Power
    Plan, so that complete repeal was “the only permissible
    interpretation of the scope of the EPA’s authority under
    [Section 7411].” ACE Rule, 84 Fed. Reg. at 32,534; see also
    id. at 32,532. “[T]hat error prevented it from a full
    consideration of the statutory question here presented.”
    Negusie v. Holder, 
    555 U.S. 511
    , 521 (2009). “Where a statute
    grants an agency discretion but the agency erroneously believes
    it is bound to a specific decision, we [cannot] uphold the result
    as an exercise of the discretion that the agency disavows,”
    United States v. Ross, 
    848 F.3d 1129
    , 1134 (D.C. Cir. 2017),
    and the “regulation must be declared invalid, even though the
    agency might be able to adopt the regulation in the exercise of
    its discretion,” Prill v. NLRB, 
    755 F.2d 941
    , 948 (D.C. Cir.
    1985) (quoting Planned Parenthood Federation of America,
    147
    Inc. v. Heckler, 
    712 F.2d 650
    , 666 (D.C. Cir. 1983) (Bork, J.,
    concurring in part and dissenting in part)); accord Arizona v.
    Thompson, 
    281 F.3d 248
    , 259 (D.C. Cir. 2002) (quoting Prill,
    
    755 F.2d at 948
    ).
    Because the ACE Rule rests squarely on the erroneous
    legal premise that the statutory text expressly foreclosed
    consideration of measures other than those that apply at and to
    the individual source, we conclude that the EPA fundamentally
    “has misconceived the law,” such that its conclusion “may not
    stand.” SEC v. Chenery Corp., 
    318 U.S. 80
    , 94 (1943).
    Accordingly, we hold that the ACE Rule must be vacated and
    remanded to the EPA so that the Agency may “consider the
    question afresh in light of the ambiguity we see.” Negusie, 
    555 U.S. at 523
     (quoting Cajun Elec. Power Coop., Inc. v. FERC,
    
    924 F.2d 1132
    , 1136 (D.C. Cir. 1991)); accord Peter Pan Bus
    Lines, Inc. v. Federal Motor Carrier Safety Admin., 
    471 F.3d 1350
    , 1354 (D.C. Cir. 2006); Prill, 
    755 F.2d at 948
    .
    VI. CONCLUSION
    Because promulgation of the ACE Rule and its embedded
    repeal of the Clean Power Plan rested critically on a mistaken
    reading of the Clean Air Act, we vacate the ACE Rule and
    remand to the Agency. We also vacate the amendments to the
    implementing regulations that extend the compliance timeline.
    Because the objections of the Coal Petitioners are without
    merit, we deny their petitions. And because the Robinson
    Petitioners lack standing, their petition is dismissed.
    So Ordered.
    WALKER, Circuit Judge, concurring in part, concurring in the
    judgment in part, and dissenting in part: This case concerns two
    rules related to climate change. The EPA promulgated both
    rules under § 111 of the Clean Air Act.1
    A major milestone in climate regulation, the first rule set
    caps for carbon emissions. Those caps would have likely
    forced shifts in power generation from higher-polluting energy
    sources (such as coal-fired power plants) to lower-emitting
    1
    When this opinion refers to § 111, it is specifically referring to
    § 111(d). The codified version of § 111(d) is titled “Standards of
    performance for existing sources; remaining useful life of source.”
    
    42 U.S.C. § 7411
    (d). The first part reads:
    (1) The Administrator shall prescribe regulations which
    shall establish a procedure similar to that provided by
    section 7410 of this title under which each State shall
    submit to the Administrator a plan which (A) establishes
    standards of performance for any existing source for any
    air pollutant (i) for which air quality criteria have not been
    issued or which is not included on a list published under
    section 7408(a) of this title or emitted from a source
    category which is regulated under section 7412 of this title
    but (ii) to which a standard of performance under this
    section would apply if such existing source were a new
    source, and (B) provides for the implementation and
    enforcement of such standards of performance.
    Regulations of the Administrator under this paragraph
    shall permit the State in applying a standard of
    performance to any particular source under a plan
    submitted under this paragraph to take into consideration,
    among other factors, the remaining useful life of the
    existing source to which such standard applies.
    
    Id.
    2
    sources (such as natural gas or renewable energy sources).2
    That policy is called generation shifting.
    Hardly any party in this case makes a serious and sustained
    argument that § 111 includes a clear statement unambiguously
    authorizing the EPA to consider off-site solutions like
    generation shifting. And because the rule implicates “decisions
    of vast economic and political significance,” Congress’s failure
    to clearly authorize the rule means the EPA lacked the authority
    to promulgate it.3
    The second rule repealed the first and partially replaced it
    with different regulations of coal-fired power plants. Dozens
    of parties have challenged both the repeal and the provisions
    replacing it.
    In my view, the EPA was required to repeal the first rule
    and wrong to replace it with provisions promulgated under
    § 111. That’s because coal-fired power plants are already
    regulated under § 112, and § 111 excludes from its scope any
    power plants regulated under § 112. Thus, the EPA has no
    authority to regulate coal-fired power plants under § 111.
    I.
    When the Constitution’s ratifiers empowered Congress to
    legislate on certain matters of national importance,4 they
    understood that federal regulation came with risks. For
    example, Congress might impose widely disbursed costs to
    2
    For ease of reading, this opinion refers to the technical term “coal-
    fired electric utility generating units” by the slightly less precise but
    lay-friendlier term “coal-fired power plants.”
    3
    Utility Air Regulatory Group v. EPA, 
    573 U.S. 302
    , 324 (2014)
    (quoting FDA v. Brown & Williamson Tobacco Corp., 
    529 U.S. 120
    ,
    160 (2000)).
    4
    U.S. CONST. art. I, § 8.
    3
    benefit insular groups in a nation of diverse economic and
    political interests. The framers called those groups factions.5
    To guard against factions, legislation requires something
    approaching a national consensus. While a single state’s
    simple majority can often subject that state to “novel social and
    economic experiments,”6 federal legislation must survive
    bicameralism and presentment.7 Only through that process can
    ideologically aligned states use federal power to impose their
    will on the unwilling.8 So too for ideologically aligned
    environmentalists. Or polluters. Or big tech. Or big labor. Or
    free traders. Or fair traders. Or farmers. Or fishers. Or
    butchers. Or bakers.
    In that process, each political institution probes legislative
    proposals from the perspective of different constituencies.9
    The House speaks for the people. The Senate, among other
    roles, guards the interests of small states. The Electoral
    College, with representation just short of proportional, strikes
    a balance between the two. And by staggering elections over
    two-, four-, and six-year cycles, we further impede fleeting
    factions from ganging up on small states and unpopular
    political minorities. The point is: It’s difficult to pass laws —
    on purpose.
    5
    See The FEDERALIST No. 10, at 56-65 (J. Madison) (J. Cooke ed.,
    1961).
    6
    New State Ice Co. v. Liebmann, 
    285 U.S. 262
    , 311 (1932) (Brandeis,
    J., dissenting).
    7
    U.S. CONST. art. I, §§ 1, 7; see INS v. Chadha, 
    462 U.S. 919
    , 951
    (1983).
    8
    Of course, even then, a legislative coalition cannot regulate outside
    Congress’s enumerated powers. See U.S. CONST. art. I, § 8.
    9
    See Department of Transportation v. Association of American
    Railroads, 
    575 U.S. 43
    , 61 (2015) (Alito, J., concurring) (“Our
    Constitution, by careful design, prescribes a process for making law,
    and within that process there are many accountability checkpoints.”).
    4
    This legislative gauntlet sometimes produces unfortunate,
    even tragic, consequences. Between the 1870s and 1960s, it
    foreclosed desperately needed civil rights laws. For budget
    hawks who predict a fiscal crisis, it has blocked entitlement
    reform. And for those who fear a climate crisis, it has
    prevented clear congressional guidance on how to cool the
    planet and who will foot the bill.10
    That, however, is the price we pay for bicameralism and
    presentment. Major regulations and reforms either reflect a
    broad political consensus, or they do not become law.
    In its clearest provisions, the Clean Air Act evinces a
    political consensus. For example, according to Massachusetts
    v. EPA, carbon dioxide is clearly a pollutant, and the Act’s
    § 202 unambiguously directs the EPA to curb pollution from
    new cars.11
    But for every carbon question answered in that case, many
    more were not even presented.12 For example, does the Clean
    Air Act force the electric-power industry to shift from fossil
    fuels to renewable resources? If so, by how much? And who
    will pay for it? Even if Congress could delegate those
    decisions, Massachusetts v. EPA does not say where in the
    Clean Air Act Congress clearly did so.
    In 2009, Congress tried to supply that clarity through new
    legislation.
    10
    Cf. Bowsher v. Synar, 
    478 U.S. 714
    , 722 (1986) (“That this system
    of division and separation of powers produces conflicts, confusion,
    and discordance at times is inherent, but it was deliberately so
    structured to assure full, vigorous, and open debate on the great
    issues affecting the people and to provide avenues for the operation
    of checks on the exercise of governmental power.”).
    11
    
    549 U.S. 497
    , 532-35 (2007).
    12
    In this opinion, “carbon” is used as shorthand for carbon dioxide
    and other greenhouse gases.
    5
    The House succeeded.13
    The President supported it.14
    But that effort stalled in the Senate.15
    Since climate change is real, man-made, and important,
    Congress’s failure to act was, to many, a disappointment. But
    the process worked as it was designed.16 In general, Senators
    from small states blocked legislation they viewed as adverse to
    their voters.17 And because small states have outsized
    influence in the Senate,18 no bill arrived on the President’s
    13
    American Clean Energy and Security Act, H.R. 2454, 111th Cong.
    (2009).
    14
    See Interview with President Obama on Climate Bill, N.Y. TIMES
    (June                             28,                           2009),
    https://www.nytimes.com/2009/06/29/us/politics/29climate-
    text.html.
    15
    See Richard Cowan & Thomas Ferraro, Senator Graham Calls
    Cap-and-Trade Plan Dead, REUTERS (Mar. 2, 2010, 2:26 PM),
    https://www.reuters.com/article/us-climate-usa-congress/senator-
    graham-calls-cap-and-trade-plan-dead-idUKTRE62142T20100302.
    16
    Cf. Association of American Railroads, 575 U.S. at 61 (Alito, J.,
    concurring) (“Bicameralism and presentment make lawmaking
    difficult by design[.]”) (cleaned up).
    17
    Due to opposition to the 2009 climate bill, it never received a
    Senate vote. The closest analogue is the 2008 climate bill, which
    received a cloture vote. And of the states with no Senator voting for
    the 2008 bill, most of those states have populations smaller than 1/50
    of the nation. Roll Call Vote 110th Congress – 2nd Session, U.S.
    SENATE,
    https://www.senate.gov/legislative/LIS/roll_call_lists/roll_call_vote
    _cfm.cfm?congress=110&session=2&vote=00145#state (all internet
    materials last visited Jan. 10, 2021).
    18
    In 2008, see supra, for twenty-four state delegations, there was no
    Senate opposition to the climate bill. That’s short of a majority of
    state delegations, and well short of the 3/5 necessary to break a
    6
    desk. Nor have dozens of other climate-related bills introduced
    since then.19
    So President Obama ordered the EPA to do what Congress
    wouldn’t.20 In 2015, after “years of unprecedented outreach
    filibuster. But those twenty-four states equal 60% of the
    population. So the Senate’s equal-state representation was
    critical. If representation were proportional to population, the
    climate bill would have been more likely to pass. Roll Call Vote
    110th      Congress      –     2nd     Session,     U.S.     SENATE,
    https://www.senate.gov/legislative/LIS/roll_call_lists/roll_call_vote
    _cfm.cfm?congress=110&session=2&vote=00145#state.
    19
    See, e.g., American Clean Energy and Security Act, H.R. 2454,
    111th Cong. (2009); Integrated Energy Systems Act, S. 2702, 116th
    Cong. (2019); Clean Industrial Technology Act, S. 2300, 116th
    Cong. (2019); Advancing Grid Storage Act, H.R. 7313, 115th Cong.
    (2018); Climate Risk Disclosure Act, S. 3481, 115th Cong. (2018);
    American Energy and Conservation Act, S. 3110, 114th Cong.
    (2016); Climate Solutions Commission Act, H.R. 6240, 114th Cong.
    (2016); Super Pollutants Act, S. 2911, 113th Cong. (2014);
    American Renewable Energy and Efficiency Act, H.R. 5301, 113th
    Cong. (2014); End Polluter Welfare Act, S. 3080, 112th Cong.
    (2012); Save Our Climate Act, H.R. 3242, 112th Cong. (2011);
    Carbon Dioxide Capture Technology Prize Act, S. 757, 112th Cong.
    (2011); Clean Energy Standard Act, S. 20, 111th Cong. (2010).
    20
    Evan Lehmann & Nathanael Massey, Obama Warns Congress to
    Act on Climate Change, or He Will, SCIENTIFIC AMERICAN (Feb. 13,
    2013), https://www.scientificamerican.com/article/obama-warns-
    congress-to-act-on-climate-change-or-he-will/ (“‘But if Congress
    won’t act soon to protect future generations, I will,’ Obama said. ‘I
    will direct my Cabinet to come up with executive actions we can
    take, now and in the future, to reduce pollution, prepare our
    communities for the consequences of climate change, and speed the
    transition to more sustainable sources of energy.’”).
    7
    and public engagement”21 — including 4.3 million public
    comments22 (about 4.25 million more than in Massachusetts v.
    EPA)23 — the EPA promulgated a rule aimed at “leading global
    efforts to address climate change.”24
    Entitled the Clean Power Plan, the EPA’s rule used the
    Clean Air Act’s § 111 to set limits for carbon emissions that
    would likely be impossible to achieve at individual coal-fired
    power plants because of costs, unavailable technologies, or a
    need to severely reduce usage.25 In that sense, the limits
    required generation shifting: shifting production from coal-
    fired power plants to facilities that use natural gas or renewable
    resources.
    To be clear, the 2015 Rule did not expressly say, “Power
    plants must adopt off-site solutions.” But it did set strict
    emission limits in part by considering off-site solutions. And
    those emission limits would likely have been unachievable or
    too costly to meet if off-site solutions were off the table.
    A political faction opposed generation shifting. It
    challenged the 2015 Rule in this Court, arguing that § 111 does
    not allow the EPA to consider off-site solutions when
    determining the best system of emission reduction. The faction
    included about twenty-four states, represented by many
    21
    FACT SHEET: Overview of the Clean Power Plan, EPA,
    https://archive.epa.gov/epa/cleanpowerplan/fact-sheet-overview-
    clean-power-plan.html.
    22
    Id.
    23
    
    549 U.S. at 511
    .
    24
    FACT SHEET: Overview of the Clean Power Plan, EPA,
    https://archive.epa.gov/epa/cleanpowerplan/fact-sheet-overview-
    clean-power-plan.html.
    25
    Respondents’ Br. at 32-37. For the codified text of § 111(d), see
    the first footnote of this opinion.
    8
    Senators who opposed the 2009 legislation.26 Conversely, a
    political faction of about eighteen states defended the rule.
    Many of their Senators had supported the stymied legislation.27
    At that litigation’s outset, our Court refused to stay the
    rule’s implementation.28 But in an unprecedented intervention,
    the Supreme Court did what this Court would not.29 And
    through its stay, the Supreme Court implied that the challengers
    would likely succeed on the case’s merits.30
    Taking the Supreme Court’s not-so-subtle hint, in 2019
    President Trump’s EPA repealed the 2015 Rule and issued the
    Affordable Clean Energy Rule. Like the rule it replaced, the
    2019 Rule relies on the Clean Air Act’s § 111 to reduce carbon
    emissions. But unlike its predecessor, the 2019 Rule did not
    include generation shifting in its final determination of the best
    system of emission reduction.
    A new faction then challenged the 2019 Rule. It looked a
    lot like the faction that had defended the 2015 Rule. Arrayed
    against that faction were many states and groups that had
    opposed the old rule. And so once again, politically diverse
    26
    See Legislative Hearing on S. 1733, Clean Energy Jobs and
    American Power Act Before the Committee on Environment and
    Public Works, 111th Cong. (2009) (For example, Senators from
    Oklahoma, Ohio, Wyoming, and Louisiana expressed opposition or
    concern about the legislation.).
    27
    See id. (For example, Senators from California, Massachusetts,
    Minnesota, New Mexico, Oregon, Rhode Island, Vermont, and
    Maryland expressed support for the legislation.).
    28
    West Virginia v. EPA, No. 15-1363 (D.C. Cir. Jan. 21, 2016) (per
    curiam) (order).
    29
    West Virginia v. EPA, 
    136 S. Ct. 1000
     (2016) (mem.).
    30
    See Winter v. Natural Resources Defense Council, 
    555 U.S. 7
    , 20
    (2008).
    9
    states and politically adverse special interest groups brought
    their political brawl into a judiciary designed to be apolitical.
    In this latest round, the briefing’s word count exceeded a
    quarter of a million words. The oral argument lasted roughly
    nine hours. The case’s caption alone runs beyond a dozen
    pages. And yet, in all that analysis, hardly any of the dozens
    of petitioners or intervenors defending the 2015 Rule make a
    serious and sustained argument that § 111 includes a clear
    statement unambiguously authorizing the EPA to consider a
    system of emission reduction that includes off-site solutions or
    that § 111 otherwise satisfies the major-rules doctrine’s clear-
    statement requirement. Neither does the EPA.
    In light of that,31 I doubt § 111 authorizes the 2015 Rule
    — arguably one of the most consequential rules ever proposed
    by an administrative agency:
    •   It required a “more aggressive transformation in the
    domestic energy industry,” marking for President
    Obama a “major milestone for his presidency.”32
    •   It aspired to reduce that industry’s carbon emissions
    by 32 percent — “equal to the annual emissions
    from more than 166 million cars.”33
    31
    Cf. ARTHUR CONAN DOYLE, Silver Blaze, in THE COMPLETE
    SHERLOCK HOLMES 312, 325 (2009) (“Before deciding that question
    I had grasped the significance of the silence of the dog, for one true
    inference invariably suggests others.”).
    32
    J.A. 2076 (White House Fact Sheet).
    33
    FACT SHEET: Clean Power Plan By The Numbers, EPA,
    https://archive.epa.gov/epa/cleanpowerplan/fact-sheet-clean-power-
    plan-numbers.html; What Is the Clean Power Plan?, NATIONAL
    RESOURCES DEFENSE COUNCIL, INC. (Sept. 29, 2017),
    https://www.nrdc.org/stories/how-clean-power-plan-works-and-
    why-it-
    10
    •   Leaders of the environmental movement considered
    the     rule   “groundbreaking,”34     called  its
    announcement “historic,”    35
    and labeled it a
    “critically important catalyst.”36
    The potential costs and benefits of the 2015 Rule are
    almost unfathomable. Industry analysts expected wholesale
    electricity’s cost to rise by $214 billion.37 The cost to replace
    shuttered capacity? Another $64 billion.38 (“A billion here, a
    billion there, and pretty soon you’re talking real money.”39)
    matters#:~:text=According%20to%20EPA%20projections%2C%20
    by,nationally%2C%20relative%20to%202005%20levels.&text=Th
    e%20shift%20to%20energy%20efficiency,its%20electricity%20bill
    s%20in%202030 (“According to EPA projections, by 2030, the
    Clean Power Plan would cut the electric sector’s carbon pollution by
    32 percent nationally, relative to 2005 levels.”).
    34
    Save the Clean Power Plan, NATIONAL RESOURCES DEFENSE
    COUNCIL, INC., https://www.nrdc.org/save-clean-power-plan.
    35
    The Clean Power Plan, ENVIRONMENTAL DEFENSE FUND,
    https://www.edf.org/clean-power-plan-resources.
    36
    Press Release, Michael Brune, Sierra Club Executive Director,
    Repealing the Clean Power Plan Will Threaten Thousands of Lives
    (Oct.        9,      2017),         https://www.sierraclub.org/press-
    releases/2017/10/repealing-clean-power-plan-will-threaten-
    thousands-lives.
    37
    EPA’s Clean Power Plan An Economic Impact Analysis, NMA, 2,
    http://nma.org/attachments/article/2368/11.13.15%20NMA_EPAs
    %20Clean%20Power%20Plan%20%20An%20Economic%20Impac
    t%20Analysis.pdf.
    38
    Id.
    39
    Senator Everett McKinley Dirksen Dies, U.S. SENATE (Sept. 7,
    1969),
    https://www.senate.gov/artandhistory/history/minute/Senator_Evere
    tt_Mckinley_Dirksen_Dies.htm; cf. id. (“Researchers have been
    unable to track down the quotation most commonly associated with
    11
    True, you can dismiss that research as industry-funded.
    But the EPA itself predicted its rule would cost billions of
    dollars and eliminate thousands of jobs.40
    On the benefits side of the ledger, the White House labeled
    the 2015 Rule a “Landmark,”41 and the President called it “the
    single most important step America has ever taken in the fight
    against global climate change.”42 With that in mind,
    calculating the rule’s benefits requires a sober appraisal of that
    fight’s high stakes. According to the rule’s advocates, victory
    over climate change will lower ocean levels; preserve glaciers;
    reduce asthma; make hearts healthier; slow tropical diseases;
    abate hurricanes; temper wildfires; reduce droughts; stop many
    floods; rescue whole ecosystems; and save from extinction up
    to “half the species on earth.”43
    Dirksen. Perhaps he never said it, but the comment would have been
    entirely in character.”).
    40
    J.A. 336; see, e.g., Regulatory Impact Analysis for the Clean
    Power Plan Final Rule, EPA, 6-25 (Oct. 23, 2015),
    https://19january2017snapshot.epa.gov/sites/production/files/2015-
    08/documents/cpp-final-rule-ria.pdf.
    41
    Fact Sheet: President Obama to Announce Historic Carbon
    Pollution Standards for Power Plants, THE WHITE HOUSE (Aug. 3,
    2015),               https://obamawhitehouse.archives.gov/the-press-
    office/2015/08/03/fact-sheet-president-obama-announce-historic-
    carbon-pollution-standards.
    42
    Andrew Rafferty, Obama Unveils Ambitious Plan to Combat
    Climate Change, NBC NEWS (Aug. 3, 2015, 3:05 PM),
    https://www.nbcnews.com/politics/barack-obama/obama-unveils-
    ambitious-plan-combat-climate-change-n403296.
    43
    FACT SHEET: Overview of the Clean Power Plan, EPA,
    https://archive.epa.gov/epa/cleanpowerplan/fact-sheet-overview-
    clean-power-plan.html; Al Gore, Al Gore: The Climate Crisis Is
    the Battle of Our Time, and We Can Win, N.Y. TIMES (Sept. 20,
    2019),        https://www.nytimes.com/2019/09/20/opinion/al-gore-
    12
    These are, to put it mildly, serious issues. Lives are at
    stake. And even though it’s hard to put a dollar figure on the
    net value on what many understandably consider invaluable,
    the EPA tried: $36 billion, it said, give or take about a $10-
    billion margin of error.44
    So say what you will about the cost-benefit analysis behind
    generation shifting, it’s hardly a minor question. Minor
    questions do not forestall consequences comparable to “the
    extinction event that wiped out the dinosaurs 65 million years
    ago.”45 Minor questions are not analogous to “Thermopylae,
    Agincourt, Trafalgar, Lexington and Concord, Dunkirk, Pearl
    Harbor, the Battle of the Bulge, Midway and Sept. 11.”46
    Minor rules do not inspire “years of unprecedented outreach
    and public engagement.”47 Minor rules are not “the single most
    climate-change.html; Effects of Climate Change, WORLD WILDLIFE
    FUND,       https://www.worldwildlife.org/threats/effects-of-climate-
    change.
    44
    FACT SHEET: Overview of the Clean Power Plan, EPA,
    https://archive.epa.gov/epa/cleanpowerplan/fact-sheet-overview-
    clean-power-plan.html.
    45
    AN INCONVENIENT TRUTH (Lawrence Bender Productions, 2006)
    (“Global warming, along with the cutting and burning of forests and
    other critical habitats, is causing the loss of living species at a level
    comparable to the extinction event that wiped out the dinosaurs 65
    million years ago. That event was believed to have been caused by
    a giant asteroid. This time it is not an asteroid colliding with the
    Earth and wreaking havoc: it is us.”).
    46
    Al Gore, Al Gore: The Climate Crisis Is the Battle of Our Time,
    and We Can Win, N.Y. TIMES (Sept. 20, 2019),
    https://www.nytimes.com/2019/09/20/opinion/al-gore-climate-
    change.html; see id. (“This is our generation’s life-or-death
    challenge.”).
    47
    FACT SHEET: Overview of the Clean Power Plan, EPA,
    https://archive.epa.gov/epa/cleanpowerplan/fact-sheet-overview-
    clean-power-plan.html.
    13
    important step America has ever taken in the fight against
    global climate change.”48 Minor rules do not put thousands of
    men and women out of work.49 And minor rules do not
    calculate $10 billion in net benefits as their margin of error.50
    Rather, the question of how to make this “the moment
    when the rise of the oceans began to slow and our planet began
    to heal”51 — and who should pay for it — requires a “decision[]
    of vast economic and political significance.”52 That standard
    is not mine. It is the Supreme Court’s. And no cocktail of
    factors informing the major-rules doctrine can obscure its
    ultimate inquiry: Does the rule implicate a “decision[] of vast
    economic and political significance”?
    48
    Andrew Rafferty, Obama Unveils Ambitious Plan to Combat
    Climate Change, NBC NEWS (Aug. 3, 2015, 3:05 PM),
    https://www.nbcnews.com/politics/barack-obama/obama-unveils-
    ambitious-plan-combat-climate-change-n403296.
    49
    See, e.g., Regulatory Impact Analysis for the Clean Power Plan
    Final       Rule,     EPA,       6-25     (Oct.     23,      2015),
    https://19january2017snapshot.epa.gov/sites/production/files/2015-
    08/documents/cpp-final-rule-ria.pdf.
    50
    FACT SHEET: Overview of the Clean Power Plan, EPA,
    https://archive.epa.gov/epa/cleanpowerplan/fact-sheet-overview-
    clean-power-plan.html.
    51
    Barack Obama, Barack Obama’s Remarks in St. Paul, N.Y. TIMES
    (June                            3,                          2008),
    https://www.nytimes.com/2008/06/03/us/politics/03text-
    obama.html.
    52
    Utility Air Regulatory Group, 573 U.S. at 324 (quoting Brown &
    Williamson Tobacco, 
    529 U.S. at 160
    ) (cleaned up); see Gonzales v.
    Oregon, 
    546 U.S. 243
    , 267 (2006) (quoting Brown & Williamson
    Tobacco, 
    529 U.S. at 160
    ) (cleaned up).
    14
    Proponents of the 2015 Rule say it doesn’t.53 They have
    to. If it did, it’s invalid — because a clear statement is
    missing.54 And according to the Supreme Court, that is exactly
    what a major rule requires.
    To be sure, if we frame a question broadly enough,
    Congress will have always answered it. Does the Clean Air
    Act direct the EPA to make our air cleaner? Clearly yes. Does
    it require at least some carbon reduction? According to
    Massachusetts v. EPA, again yes.
    But how should the EPA reduce carbon emissions from
    power plants? And who should pay for it? To those major
    questions, the Clean Air Act’s answers are far from clear.
    I admit the Supreme Court has proceeded with baby steps
    toward a standard for its major-rules doctrine. But “big things
    have small beginnings.”55 And even though its guidance has
    been neither sweeping nor precise, the Supreme Court has at
    least drawn this line in the sand: Either a statute clearly
    endorses a major rule, or there can be no major rule.56
    Moreover, if Congress merely allowed generation shifting
    (it didn’t), but did not clearly require it, I doubt doing so was
    constitutional. For example, imagine a Congress that says,
    “The EPA may choose to consider off-site solutions for its best
    system of emission reduction, but the EPA may choose not to
    consider off-site solutions.” In that instance, Congress has
    53
    See Oral Arg. Tr. at 23 (Counsel for State and Municipal
    Petitioners on the 2015 Rule: “We do not think it implicates the
    Major Questions Doctrine here for a couple of reasons.”).
    54
    See supra p. 9.
    55
    LAWRENCE OF ARABIA (Columbia Pictures, 1962).
    56
    MCI Telecommunications Corp. v. American Telephone &
    Telegraph Co., 
    512 U.S. 218
    , 230-31 (1994); Brown & Williamson
    Tobacco, 
    529 U.S. at 126-27, 133
    ; Gonzales, 
    546 U.S. at 267
    ; Utility
    Air Regulatory Group, 573 U.S. at 322-25.
    15
    clearly delegated to the EPA its legislative power to determine
    whether generation shifting should be part of the best system
    of emission reduction — a “decision[] of vast economic and
    political significance.”57
    Such delegation might pass muster under a constitution
    amended by “moments” rather than the “reflection and choice”
    prescribed by Article V.58 But if ever there was an era when
    an agency’s good sense was alone enough to make its rules
    good law, that era is over.59
    Congress decides what major rules make good sense. The
    Constitution’s First Article begins, “All legislative Powers
    herein granted shall be vested in a Congress of the United
    States, which shall consist of a Senate and House of
    Representatives.”60 And every “law” must “pass[] the House
    of Representatives and the Senate” and “be presented to the
    President.”61 Thus, whatever multi-billion-dollar regulatory
    57
    Utility Air Regulatory Group, 573 U.S. at 324 (2014) (quoting
    Brown & Williamson Tobacco, 
    529 U.S. at 160
    ) (cleaned up); see
    also Gonzales, 
    546 U.S. at 267
     (quoting Brown & Williamson
    Tobacco, 
    529 U.S. at 160
    ).
    58
    See U.S. CONST. art. V; compare BRUCE ACKERMAN, We the
    People: Foundations 22 (1991) (“moments”) with MICHAEL S.
    GREVE, The Upside-Down Constitution 13 (2012) (“reflection and
    choice”) (quoting The FEDERALIST No. 1, at 3-7 (A. Hamilton) (J.
    Cooke ed., 1961)).
    59
    See, e.g., SAS Institute, Inc. v. Iancu, 
    138 S. Ct. 1348
    , 1358-59
    (2018) (“The Director may (today) think his approach makes for
    better policy, but policy considerations cannot create an ambiguity
    when the words on the page are clear. Neither may we defer to an
    agency official’s preferences because we imagine some hypothetical
    reasonable legislator would have favored that approach. Our duty is
    to give effect to the text that actual legislators (plus one President)
    enacted into law.”) (cleaned up).
    60
    U.S. CONST. art. I, § 1.
    61
    Id. § 7.
    16
    power the federal government might enjoy, it’s found on the
    open floor of an accountable Congress, not in the impenetrable
    halls of an administrative agency — even if that agency is an
    overflowing font of good sense.62
    Over time, the Supreme Court will further illuminate the
    nature of major questions and the limits of delegation. And
    under that caselaw, federal regulation will undoubtedly endure.
    So will federal regulators. Administrative agencies are
    constitutional, and they’re here to stay.63
    Beyond that, I leave it for others to predict what the
    Supreme Court’s emerging jurisprudence may imply for those
    agencies’ profiles.     Here, regardless of deference and
    delegation doctrines, the regulation of coal-fired power plants
    under § 111 is invalid for a more mundane reason: A 1990
    amendment to the Clean Air Act forbids it.
    62
    See id.; id. § 1; A.L.A. Schechter Poultry Corp. v. United States,
    
    295 U.S. 495
     (1935); Marshall Field & Co. v. Clark, 
    143 U.S. 649
    ,
    692 (1892); Gundy v. United States, 
    139 S. Ct. 2116
    , 2130-31 (2019)
    (Alito, J., concurring in the judgment); see generally MIKE LEE, Our
    Lost Constitution (2015); PHILIP HAMBURGER, Is Administrative
    Law Unlawful? (2014); Cody Ray Milner, Comment, Into the
    Multiverse: Replacing the Intelligible Principle Standard With a
    Modern Multi-Theory of Nondelegation, 28 GEO. MASON L. REV.
    395 (2020); cf. Talk America, Inc. v. Michigan Bell Telephone Co.,
    
    564 U.S. 50
    , 68 (2011) (Scalia, J., concurring) (“When the legislative
    and executive powers are united in the same person, or in the same
    body of magistrates, there can be no liberty . . . .”) (quoting
    MONTESQUIEU, Spirit of the Laws bk. XI, ch. 6, pp. 151-52 (O. Piest
    ed., T. Nugent transl. 1949)); In re Aiken County, 
    725 F.3d 255
    , 264
    (D.C. Cir. 2013) (same).
    63
    Gundy, 
    139 S. Ct. at 2145
     (Gorsuch, J., dissenting) (“Nor would
    enforcing the Constitution’s demands spell doom for what some call
    the administrative state.”) (cleaned up).
    17
    II.
    The Clean Air Act Amendments of 1990 prohibit the EPA
    from subjecting power plants to regulation under § 111 if they
    are already regulated under § 112. The 2015 Rule and the 2019
    Rule rely on § 111 for the authority to regulate coal-fired power
    plants. Because the EPA already regulates those coal-fired
    power plants under § 112, the rules are invalid.
    A.
    Before 1990, the Clean Air Act’s § 112 told the EPA to
    create a list of hazardous air pollutants. Section 112 directed
    the EPA to regulate the pollutants on that list. And § 111
    provided authorization to regulate pollutants not on that list.
    Carbon is not on the § 112 list. So, under the pre-1990
    scheme, the EPA could regulate carbon under § 111.
    But Congress amended § 112 in 1990. Rather than just
    telling the EPA to make a § 112 list of pollutants, Congress
    created its own § 112 list.
    That same year, Congress also amended § 111. As a result,
    the codified version of § 111 prohibits the regulation of
    pollutants “emitted from a source category which is regulated
    under [§ 112].”64
    Coal-fired power plants are a source regulated under
    § 112.65 Therefore, under the codified version of the Clean Air
    Act, coal plants cannot be regulated under § 111. And since
    the 2015 Rule and the 2019 Rule use § 111 to regulate carbon
    emitted from coal plants, those rules purport to do what the
    codified version of § 111 says the EPA cannot.
    But that is not the whole story. Congress’s Office of the
    Law Revision Counsel codifies statutes. And when it
    64
    
    42 U.S.C. § 7411
    (d) (emphasis added).
    65
    Their mercury emissions are regulated under § 112.
    18
    mistakenly codifies text different from the Statutes at Large,
    the Statutes at Large controls.66 And the Statutes at Large
    differs from the codified text here.
    The question concerns two amendments, one from each
    house of Congress, which both ended up in the final bill.67
    Under the House Amendment:
    The      Administrator      shall     prescribe
    regulations . . . under which each State shall
    submit to the Administrator a plan which (A)
    establishes standards of performance for any
    existing source for any air pollutant (i) for
    which air quality criteria have not been issued
    or which is not included on a list published
    under section 7408(a) of this title or emitted
    from a source category which is regulated
    under section 112 [of the Clean Air Act.]68
    66
    Cheney Railroad Co. v. Railroad Retirement Board, 
    50 F.3d 1071
    ,
    1076 (D.C. Cir. 1995); see also United States National Bank of
    Oregon v. Independent Insurance Agents of America, Inc., 
    508 U.S. 439
    , 448 & n.3 (1993).
    67
    The section, before the 1990 Amendments, read:
    The Administrator shall prescribe regulations which
    shall establish a procedure . . . under which each
    State shall submit to the Administrator a plan which
    (A) establishes standards of performance for any
    existing source for any air pollutant (i) for which air
    quality criteria have not been issued or which is not
    included on a list published under section 7408(a) or
    7412(b)(1)(A) of this title . . . .
    
    42 U.S.C. § 7411
    (d)(1) (1988) (emphasis added).
    68
    Pub. L. No. 101-549, § 108(g), 
    104 Stat. 2399
    , 2467 (1990)
    (emphasis added); 
    42 U.S.C. § 7411
    (d)(1).
    19
    Under the Senate Amendment:
    The      Administrator      shall       prescribe
    regulations . . . under which each State shall
    submit to the Administrator a plan which (A)
    establishes standards of performance for any
    existing source for any air pollutant (i) for
    which air quality criteria have not been issued
    or which is not included on a list published
    under section 7408(a) of this title or 112(b) [of
    the Clean Air Act.]69
    Let’s compare those two versions with the most relevant
    text bolded, the divergent text underlined, and the other text
    struck through.
    House Version:
    The      Administrator      shall     prescribe
    regulations . . . under which each State shall
    submit to the Administrator a plan which (A)
    establishes standards of performance for any
    existing source for any air pollutant (i) for
    which air quality criteria have not been issued
    or which is not included on a list published
    under section 7408(a) of this title or emitted
    from a source category which is regulated
    under section 112 . . . .
    Senate Version:
    The      Administrator      shall   prescribe
    regulations . . . under which each State shall
    submit to the Administrator a plan which (A)
    establishes standards of performance for any
    existing source for any air pollutant (i) for
    69
    Pub. L. No. 101-549, § 302(a), 
    104 Stat. 2399
    , 2574 (1990)
    (emphasis added).
    20
    which air quality criteria have not been issued
    or which is not included on a list published
    under section 7408(a) of this title or
    112(b) . . . .
    Finally, let’s look at only the most relevant text.
    House:
    The Administrator shall prescribe regulations
    for any air pollutant which is not emitted from
    a source category which is regulated under
    section 112.
    Senate:
    The Administrator shall prescribe regulations
    for any air pollutant which is not included on
    a list published under 112(b).
    To sum up so far, in my view:
    •   The House said the EPA can’t use § 111 to regulate
    pollutants emitted from a source category regulated
    under § 112.70
    o Coal-fired power plants are a source
    category regulated under § 112.
    •   The Senate said the EPA can’t use § 111 to regulate
    pollutants published under § 112.
    o Carbon is not a pollutant published under
    § 112.
    Some parties argue the House and Senate Amendments
    conflict with each other or otherwise produce an absurd result.
    Others say they don’t. In my view, it doesn’t matter. If there’s
    70
    The EPA adopts a different interpretation of the House
    Amendment. That interpretation is addressed below in Part II.C.
    21
    a conflict, the House Amendment controls. And if there’s no
    conflict, the Senate Amendment takes nothing away from the
    House Amendment. In either scenario — conflict or no
    conflict — regulation of coal-fired power plants under § 111 is
    invalid.
    B.
    Let’s start with the first scenario: Assume the two
    amendments conflict.71 If that creates an absurd result, “a
    mistake of expression (rather than of legislative wisdom) [may
    have] been made.”72 Such a mistake of expression — a
    “scrivener’s error” — is typically viewed as a typo.73 Where
    the reading “makes entire sense grammatically but produces a
    disposition that makes no substantive sense,” a “drafter’s error”
    may exist.74 That said, the distinction between a scrivener’s
    error and a drafter’s error “is generally not a principled one.”75
    Here, the Senate and House Amendments do not have obvious
    typos or mistakes, but some may think that including both in
    the statute “makes no substantive sense” — in the same way
    71
    Cf. 
    70 Fed. Reg. 15,994
    , 16,030-32 (Mar. 29, 2005) (“EPA is
    therefore confronted with the highly unusual situation of an enacted
    bill signed by the President that contains two different and
    inconsistent amendments to the same statutory provision.”).
    72
    Antonin Scalia, Common-Law Courts in a Civil-Law System: The
    Role of United States Federal Courts in Interpreting the Constitution
    and Laws, in A MATTER OF INTERPRETATION: FEDERAL COURTS
    AND THE LAW 3, 20 (Amy Gutmann ed., 1997); see also West
    Virginia v. EPA, No. 15-1363, Oral Arg. Tr. at 111 (Kavanaugh, J.)
    (“When [a conflict] happens[,] you [may] have a scrivener’s error.”).
    73
    See ANTONIN SCALIA & BRYAN A. GARNER, Reading Law: The
    Interpretation of Legal Texts 234 (2012) (quoting Daniel A. Farber,
    Statutory Interpretation and Legislative Supremacy, 
    78 Geo. L.J. 281
    , 289 (1989)).
    74
    
    Id. at 235
    .
    75
    
    Id.
    22
    that a single order to “always drive fast” and “never drive fast”
    makes no substantive sense.
    In these rare circumstances, judges may read the text in a
    way that accounts for these errors. In doing so, “we are not
    revising the apparent meaning of the text.”76 Instead, we give
    the text “the meaning that it would convey to a reasonable
    person, who would understand that misprints had occurred.”77
    But the “meaning genuinely intended but inadequately
    expressed must be absolutely clear; otherwise we might be
    rewriting the statute rather than correcting a technical
    mistake.”78
    How then to discover the “meaning genuinely intended”?
    Some might say “defer to the EPA” because of the text’s
    ambiguity. But unintentional ambiguity from a drafter’s error
    is nothing like the intentional ambiguity that typically receives
    Chevron deference. Chevron applies to deliberate gaps for an
    76
    Id.; see also 
    id. at 234
     (quoting Grey v. Pearson, [1857] 6 H.L.
    Cas. 61, 106 (per Lord Wensleydale)) (cleaned up).
    77
    
    Id. at 235
    .
    78
    United States v. X-Citement Video, Inc., 
    513 U.S. 64
    , 82 (1994)
    (Scalia, J., dissenting).
    23
    agency to fill.79 So deference is arguably faithful to a statute’s
    meaning — at least in theory.80
    In contrast, drafter’s errors are accidents. So there’s no
    reason to believe deference was “genuinely intended.” And to
    the extent an office or agency with expertise is entitled to
    deference here — none is81 — Congress’s Office of the Law
    Revision Counsel is the leading candidate. Its whole job is to
    produce the United States Code, and it dismissed the Senate
    Amendment as a drafter’s error.
    Others might say the default should be freedom from
    regulation when a drafter’s error creates ambiguity over an
    agency’s authority to promulgate a major rule. After all, if
    Congress doesn’t clearly endorse a major regulation, there can
    be no major regulation.82
    79
    Chevron, U.S.A., Inc. v. Natural Resources Defense Council, Inc.,
    
    467 U.S. 837
    , 862 (1984); cf. Pereira v. Sessions, 
    138 S. Ct. 2105
    ,
    2121 (2018) (Kennedy, J., concurring) (“Given the concerns raised
    by some Members of this Court it seems necessary and appropriate
    to reconsider, in an appropriate case, the premises that
    underlie Chevron and how courts have implemented that
    decision. The proper rules for interpreting statutes and determining
    agency jurisdiction and substantive agency powers should accord
    with constitutional separation-of-powers principles and the function
    and province of the Judiciary.”) (cleaned up).
    80
    But see Gutierrez-Brizuela v. Lynch, 
    834 F.3d 1142
    , 1153 (10th
    Cir. 2016) (Gorsuch, J., concurring) (“The fact is, Chevron’s claim
    about legislative intentions is no more than a fiction — and one that
    requires a pretty hefty suspension of disbelief at that.”).
    81
    Ganem v. Heckler, 
    746 F.2d 844
    , 851 (D.C. Cir. 1984) (“[T]he
    changes made by the codifiers, whose choice, made without the
    approval of Congress[,] should be given no weight, are of no
    substantive moment.”) (cleaned up).
    82
    See MCI Telecommunications, 
    512 U.S. at 230-31
    ; Brown &
    Williamson Tobacco, 
    529 U.S. at 126-27, 133
    ; Gonzales, 
    546 U.S. at 267
    ; Utility Air Regulatory Group, 573 U.S. at 322-25.
    24
    But as with Chevron, the major-rules doctrine draws
    meaning from ambiguity: Because Congress does not hide
    elephants in mouseholes, we presume the absence of clarity
    means Congress intentionally chose not to endorse a major
    regulation. So as with Chevron’s premise, the premise of the
    major-rules doctrine is inapplicable to a drafter’s error. Here,
    to the extent an elephant’s in a mousehole, we don’t know
    whether the misprint is the mousehole or the elephant.
    That leaves us with a third option: inquiring into legislative
    history. True, as a general matter, courts should reject any
    significant reliance on legislative history. Hamilton did.83 So
    did Marshall.84 And Madison.85 And Story.86 “From the
    beginnings of the republic, American law followed what is
    known as the ‘no-recourse doctrine’ — that in the
    interpretation of a text, no recourse may be had to legislative
    history.”87 And although many judges abandoned the no-
    recourse doctrine by the second half of the twentieth century,88
    leading textualists like Justice Scalia have made important
    progress in reviving it.
    But “[w]hen you have a scrivener’s error[,] everyone,
    including Justice Scalia, would look at the legislative
    history.”89 Indeed, he “believed that the only time it was
    83
    ANTONIN SCALIA & BRYAN A. GARNER, Reading Law: The
    Interpretation of Legal Texts 370 (2012).
    84
    Id. at 370-71.
    85
    Id. at 371.
    86
    Id. at 371-72.
    87
    Id. at 369.
    88
    Id. at 388.
    89
    West Virginia v. EPA, No. 15-1363, Oral Arg. Tr. at 111
    (Kavanaugh, J.); see also John Copeland Nagle, CERCLA’s
    Mistakes, 38 WM. & MARY L. REV. 1405, 1414 (1997) (“[E]ven
    textualists like Justice Scalia acknowledge that the courts can remedy
    a ‘scrivener’s error’ notwithstanding plain statutory language.”).
    25
    appropriate for a court to use legislative history was when there
    was a credible claim of scrivener’s error.”90 For example,
    concurring in the judgment in Green v. Bock Laundry Machine
    Co., Justice Scalia considered “it entirely appropriate to
    consult . . . legislative history . . . to verify that what seems . . .
    an unthinkable disposition . . . was indeed unthought of, and
    thus to justify a departure from the ordinary meaning of the
    word” at issue.91
    So, to recap: (1) The House and Senate Amendments may
    conflict; (2) if they do, there may have been a drafter’s error;
    and (3) legislative history can illuminate a drafter’s error.
    What then, if anything, does the legislative history tell us?
    (Buckle up.)
    In 1990, the House passed a bill with many amendments
    to the Clean Air Act. The Senate passed a different bill. A
    Conference Committee reconciled them. But it made (at least)
    two drafter’s errors — assuming again our two amendments
    conflict.
    First, the Conference Committee put both the House and
    Senate Amendments in the Conference Report, which became
    the final bill.92
    90
    Megan McDermott, Justice Scalia’s Bankruptcy Jurisprudence:
    The Right Judicial Philosophy for the Modern Bankruptcy Code?,
    2017 UTAH L. REV. 939, 974 (2017) (emphasis added).
    91
    
    490 U.S. 504
    , 527 (1989) (Scalia, J., concurring in the judgment).
    92
    The Conference Report says “[t]hat the Senate recede[s] from its
    disagreement to the amendment of the House to the text of the bill
    and agree[s] to the same with an amendment as follows: In lieu of
    the matter proposed to be inserted by the House amendment insert
    the following: . . . Sec. 108. Miscellaneous provisions.” H.R. Rep.
    No. 101-952, 101st Cong., at 1 (1990) (cleaned up). Section 108(g)
    under “Miscellaneous provisions” was the House Amendment that
    26
    Second, the Conference Committee botched the “Joint
    Explanatory Statement of the Committee of Conference.”93
    The Joint Statement said, “The House amendment to the
    text of the bill struck out all of the Senate bill after the enacting
    clause and inserted a substitute text.”94 That “amendment”
    refers to the House’s entire set of amendments to the Clean Air
    Act. Clear enough so far.
    The Joint Statement then said, “The Senate recedes from
    its disagreement to the amendment of the House . . . .”95
    Again, that seems straightforward.
    But the Joint Statement didn’t stop there. The full sentence
    excerpted just above says:
    The Senate recedes from its disagreement to the
    amendment of the House with an amendment
    which is a substitute for the Senate bill and the
    House amendment.96
    That is drivel. The Senate recedes with an amendment?
    What amendment? And how is that receding? And did the
    House recede to the Senate’s amendment to the House’s
    amendment that the Senate receded to?
    The next day, the bill’s Senate Managers issued a
    statement attempting to clarify the previous day’s materials.
    struck “or 112(b)(1)(A)” and inserted “or emitted from a source
    category which is regulated under section 112.” Id. at 73. But later
    in the report we find the Senate’s original proposed amendment —
    replacing “112(b)(1)(A)” with “112(b).” Id. at 183. So the Senate
    says it receded to the House, and yet we still see the Senate’s original
    language in the document.
    93
    Id. at 335-55.
    94
    Id. at 335.
    95
    Id.
    96
    Id.
    27
    The statement notes that for two unrelated portions of the § 111
    amendments, the House receded to the Senate.97 But it said the
    Senate receded to the House regarding all other § 111 changes,
    including the change at issue in this case.98
    To the extent a statement by Senate Managers can ever
    clear up a question of statutory meaning — count me
    skeptical99 — theirs did.
    Here’s where that leaves me. I’m frankly not convinced
    the House and Senate Amendments are the product of a
    drafter’s error. But if they are, the most lucid piece of
    legislative history says the Senate intended to recede to the
    House.
    That would leave the House Amendment as the last man
    standing. And under the House Amendment, the EPA can’t
    regulate air pollutants from coal-fired power plants under § 111
    when the plants are already regulated under § 112. Therefore,
    if the House and Senate Amendments conflict, the 2015 Rule
    and the 2019 Rule are invalid.100
    97
    Chafee-Baucus Statement of Senate Managers, S. 1630, the Clean
    Air Act Amendments of 1990, 136 Cong. Rec. 36007, 36067 (Oct. 27,
    1990).
    98
    Id. The full sentence about the two amendments at issue here
    reads: “Conference agreement. The Senate recedes to the House
    except that with respect to the requirement regarding judicial review
    of reports, the House recedes to the Senate and with respect to
    transportation planning, the House recedes to the Senate with certain
    modifications.” In other words, except for judicial review of reports
    (immaterial here) and transportation planning (immaterial here), the
    Senate receded to the House.
    99
    Environmental Defense Fund, Inc. v. EPA, 
    82 F.3d 451
    , 460 n.11
    (D.C. Cir. 1996).
    100
    The EPA doesn’t like that result. For thirty years it has either
    ignored or misconstrued the House Amendment. But the EPA’s
    28
    C.
    As for the second (and more likely) of the two scenarios:
    Assume the House and Senate Amendments do not conflict. In
    that case, we don’t strike the Senate Amendment as a drafter’s
    error.101 But even then, the House Amendment retains its full
    effect.
    Recall that each amendment does two things. First,
    it creates a category of air pollutants. And second, it excludes
    that category from regulations authorized under § 111.
    For the House Amendment, that category covers any
    pollutant “emitted from a source category which is regulated
    under section 112.” And for the Senate Amendment, that
    category covers any pollutant “published under
    section . . . 112(b).”
    So to see what’s in the House Amendment’s category,
    you’d start by making a list of every source regulated under
    § 112. As far as § 111 regulation goes, any air pollutants from
    those sources — including coal-fired power plants — are
    forbidden fruit under the House Amendment.
    To create the Senate Amendment’s list, you’d simply pull
    the 180 or so pollutants from § 112(b), as modified by the EPA
    since 1990. As far as § 111 regulation goes, those pollutants
    long-running error is no reason to ignore plain text. To the extent I
    glean anything from the EPA’s thirty-year mistake, it’s that the EPA
    might be entitled to less deference than it thinks it deserves.
    101
    For the reader’s convenience, here again is the codified version of
    § 111(d): “The Administrator shall prescribe regulations which shall
    establish a procedure . . . under which each State shall submit to the
    Administrator a plan which (A) establishes standards of performance
    for any existing source for any air pollutant (i) for which air
    quality criteria have not been issued or which is not included on
    a list published under [§ 108(a)] or emitted from a source
    category which is regulated under [§ 112] . . . .” (emphasis added).
    29
    — mercury compounds, asbestos, and more than 180 others —
    are forbidden fruit under the Senate Amendment.102
    In general, the House Amendment sweeps more broadly
    than the Senate Amendment. For example, the House
    Amendment’s list includes pollution from coal-fired power
    plants, since they are regulated for mercury. So under the
    House Amendment, § 111 cannot be used to regulate coal-fired
    power plants at all.
    In contrast, the Senate Amendment’s list includes
    mercury, but it does not include all other pollution from
    sources that emit mercury. So under the Senate Amendment,
    § 111 cannot be used to regulate coal-fired power plants’
    emissions of mercury. But the Senate Amendment does not by
    itself stop the EPA from using § 111 to regulate coal-fired
    power plants’ emissions of pollutants like carbon, since carbon
    isn’t on the Senate Amendment’s list.
    That the House Amendment generally sweeps more
    broadly than the Senate Amendment, however, does not mean
    that fidelity to the House Amendment fails to give full effect to
    the Senate Amendment. For example, imagine two parents
    choosing a name for their child. The father says, “There’s no
    way we’re naming our baby after a president from Virginia.”
    And the mother says, “There’s no way we’re naming our baby
    after any president.”
    Just like the House and the Senate each took certain
    regulations off § 111’s table, the mother and father have each
    taken certain names off the table. And just as the House
    Amendment excludes from § 111 every regulation excluded by
    102
    Initial List of Hazardous Air Pollutants with Modifications, EPA,
    https://www.epa.gov/haps/initial-list-hazardous-air-pollutants-
    modifications.
    30
    the Senate Amendment (and then some), the mother has said
    no way to every name excluded by the father (and then some).
    When you give full effect to the mother’s no-way list, you
    are not ignoring the father’s no-way list — because the father’s
    list only excludes names and thus does not require the inclusion
    of any names. And for the same reason, when you give full
    effect to the father’s list, you are not ignoring the mother’s —
    because the mother’s no-way list does not require the inclusion
    of names excluded by the father.
    Like the father’s list, the Senate Amendment has a lot to
    say about what’s excluded from § 111. But like the father’s
    list, the Senate Amendment says nothing about what’s
    included. So when the House Amendment excludes coal-fired
    power plants from § 111’s scope, it doesn’t ignore the Senate
    Amendment. It supplements it — by excluding from § 111’s
    scope a category of regulations not already excluded by the
    Senate Amendment.
    That’s the situation that will occur most often — air
    pollutants excluded from § 111 regulation because they’re on
    the Senate Amendment’s list will also be excluded from § 111
    regulation because they’re on the House Amendment’s list.
    But there may exist situations, at least in theory, when only
    the Senate Amendment does any work.
    For example, consider a hazardous air pollutant listed
    under § 112 but “emitted by sources that Section [112] does not
    reach.”103 That pollutant is barred from § 111 regulation by the
    Senate Amendment (because it’s a pollutant listed under
    § 112), but it is arguably not barred by the House Amendment
    (because it’s emitted from a source not regulated under § 112).
    103
    Majority Op. at 119-20 n.19.
    31
    In that scenario, it’s possible only the Senate Amendment
    would bar § 111 regulation.104
    In other words, these § 111 exclusions might form a Venn
    diagram: Some air pollutants are excluded from § 111
    regulation only because of the House Amendment (like carbon
    from coal-fired power plants), some pollutants are only
    excluded because of the Senate Amendment (as in the
    hypothetical I just described), and some pollutants are excluded
    because of both amendments (like mercury from coal-fired
    power plants). Recognizing both amendments as operative
    gives “maximum possible effect” to each.105
    The EPA says Chevron applies to this question. Even so,
    the outcome is the same. At Chevron step one, the plain text
    of the Senate Amendment takes nothing away from the plain
    text of the House Amendment and vice versa. And because the
    House Amendment expressly precludes the regulation of coal-
    fired power plants under § 111, the plain text precludes the
    2015 Rule and the 2019 Rule — both of which depended on
    § 111 to regulate coal-fired power plants.
    In American Electric Power Co. v. Connecticut, the
    Supreme Court agreed with this reading. It said the “EPA may
    not employ § [111(d)] if existing stationary sources of the
    pollutant in question are regulated under the national ambient
    104
    As another theoretical example, consider a source that emits a
    pollutant on § 112’s list and assume the EPA is required to regulate
    that source based on § 112’s parameters. But now imagine that,
    notwithstanding that requirement, the EPA has not yet regulated the
    source. After all, sometimes these things take time. In that situation
    too, the Senate Amendment might exclude from § 111 regulation
    pollutants that the House Amendment might not (yet).
    105
    Citizens to Save Spencer County v. EPA, 
    600 F.2d 844
    , 870 (D.C.
    Cir. 1979).
    32
    air quality standard program . . . or the ‘hazardous air
    pollutants’ program, § [112].”106
    The EPA adopts a different approach to the House
    Amendment. In “any air pollutant . . . emitted from a source
    category which is regulated under section 112,” the EPA reads
    the phrase “which is regulated under section 112” to modify
    “air pollutant,” rather than “source category.” So it would
    exclude from § 111’s scope only an “air pollutant . . . which is
    regulated under § 112”:
    106
    American Electric Power Co. v. Connecticut, 
    564 U.S. 410
    , 424
    n.7 (2011) (citing § 7411(d)(1)). The EPA notes that this footnote
    was dicta and that it conflicted with national ambient air quality
    standard regulations at the time. But the EPA can’t have it both
    ways: It can’t dismiss an inconvenient part of American Electric
    Power that is directly on point and then rely on other parts of that
    case where the precise meaning and contours of § 111(d) were not at
    issue.
    As for American Electric Power’s holding, it depended on the
    Supreme Court’s understanding that § 111(d) “speaks directly” to
    carbon emissions from fossil-fuel plants. Id. at 424. I agree that
    § 111(d) “speaks directly” to whether the EPA can or cannot regulate
    carbon from coal-fired power plants: The provision directly says that
    the EPA can regulate pollutants from existing sources unless the EPA
    already regulates those sources under § 112. Compare id. with id. at
    424 n.7.
    33
    The      Administrator      shall     prescribe
    regulations . . . under which each State shall
    submit to the Administrator a plan which (A)
    establishes standards of performance for any
    existing source for any air pollutant (i) for
    which air quality criteria have not been issued
    or which is not included on a list published
    under section 108(a) or emitted from a source
    category which         is   regulated under
    section 112 . . . .
    To get to the EPA’s preferred reading — to make “which
    is regulated by section 112” modify “air pollutant” — the EPA
    needs to read into § 111(d)(1)(A)(i) a triplet of three
    whiches:107
    The       Administrator     shall      prescribe
    regulations . . . under which each State shall
    submit to the Administrator a plan which (A)
    establishes standards of performance for any
    existing source for any air pollutant [1] for
    which air quality criteria have not been issued
    or [2] which is not included on a list published
    under § 108(a) or emitted from a source
    category [3] which is [not] regulated under
    § 112 . . . .
    My alterations — including [1], [2], [3], and [not] —
    reflect the tripartite division implied by the EPA. But of course
    the alterations were not in the original. If they were, the EPA’s
    grammatically unconventional reading might work. They’re
    not, so it doesn’t.
    For four reasons, the EPA’s approach is not persuasive.
    107
    Cf. WILLIAM SHAKESPEARE, MACBETH act 1, sc. 1.
    34
    First, “ordinarily, and within reason, modifiers and
    qualifying phrases attach to the terms that are nearest.”108
    Under that canon, a modifying phrase, such as “which is
    regulated under section 112,” should apply to the closest noun
    possible — “source category,” not “air pollutant.”
    Second, the EPA all but reads out of § 111 the following
    words: “emitted from a source category.” To be sure, Congress
    will sometimes “include words that add nothing of substance,”
    so the canon against surplusage has limits.109 That’s why “a
    court may well prefer ordinary meaning to an unusual meaning
    that will avoid surplusage.”110 But amputating the words
    “emitted from a source category” does not clarify § 111’s
    “ordinary meaning.” Instead, doing so transforms that
    meaning.
    Third, and most importantly, Congress put a conjunction
    (“or”) between parts one and two of the imagined triplet, but
    not between parts two and three. If the EPA’s triplet exists,
    Congress’s approach to English was, to put it kindly, novel.
    In formal English, you usually separate a triplet with a
    conjunction between the second and third parts. (Life, liberty,
    or property.) Informal English sometimes puts a conjunction
    between the first and second, and between the second and third.
    (Life or liberty or property.) Sometimes you see a triplet with
    no conjunction. (Life, liberty, property.) But you rarely if ever
    see a triplet’s conjunction separate the first and second parts
    108
    Grecian Magnesite Mining, Industrial & Shipping Co., SA v.
    Commissioner, 
    926 F.3d 819
    , 824 (D.C. Cir. 2019); see also
    Lockhart v. United States, 
    136 S. Ct. 958
    , 962 (2016); ANTONIN
    SCALIA & BRYAN A. GARNER, Reading Law: The Interpretation of
    Legal Texts 144-46 (2012).
    109
    ANTONIN SCALIA & BRYAN A. GARNER, Reading Law: The
    Interpretation of Legal Texts 176 (2012).
    110
    
    Id.
    35
    without also separating the second and third parts. (Life or
    liberty property). That’s why it’s not:
    •   Stop and drop roll; or
    •   Red and white blue; or
    •   Reduce and reuse recycle; or
    •   Blood and sweat tears; or
    •   Huey and Dewey Louie.
    Thus, the EPA would require us to read into § 111 a triplet
    written in a way no one writes.111
    Fourth and finally, the EPA says a plain-text reading of the
    House Amendment would leave § 111 almost no work to do.
    111
    Whatever else the savings clause in § 112(d)(7) might save, it
    can’t save that. Cf. 
    42 U.S.C. § 7412
    (d)(7) (“No emission standard
    or other requirement promulgated under this section shall be
    interpreted, construed or applied to diminish or replace the
    requirements of a more stringent emission limitation or other
    applicable requirement established pursuant to section 7411 of this
    title, part C or D, or other authority of this chapter or a standard
    issued under State authority.”).
    Note that § 112(d)(7) applies only to requirements “established
    pursuant to” § 111. And even the EPA says regulations cannot be
    established pursuant to § 111 if they target pollutants already
    regulated under § 112. See also American Electric Power, 
    564 U.S. at
    424 n.7. So everyone agrees the § 111 amendments exclude
    something from § 111 based on § 112. And § 112(d)(7) does not
    cover whatever is excluded.
    What’s more, § 111(d)’s exclusion is more specific than
    § 112(d)(7)’s generalities, and the specific usually controls the
    general. See ANTONIN SCALIA & BRYAN A. GARNER, Reading Law:
    The Interpretation of Legal Texts 183 (2012).
    36
    But if so, that was a choice for Congress. After all, the 1990
    Clean Air Act Amendments added more than one hundred
    pollutants to § 112’s scope, with a mechanism for the EPA to
    add even more later.112 Maybe Congress thought § 111(d)
    shouldn’t be much more than a rarely used gap-filler in light of
    a beefed up § 112 — at least until Congress passed another law
    saying otherwise.
    Of course, in the end, it doesn’t matter what Congress was
    thinking.113 “It is the law that governs, not the intent of the
    lawgiver.”114 That’s because, among other reasons, “it is
    simply incompatible with democratic government, or indeed,
    even with fair government, to have the meaning of a law
    determined by what the lawgiver meant, rather than by what
    the lawgiver promulgated.”115
    Thus, an oddity of timing doesn’t trigger Chevron
    deference.116 Nor does ambiguity arise every time an agency
    wishes a statutory provision did more work than it does. When
    statutory text informed by structure and context is clear, “that
    is the end of the matter.”117
    112
    Pub. L. No. 101-549, § 301, 
    104 Stat. 2399
    , 2532-37 (1990).
    113
    Cf. Gutierrez-Brizuela, 834 F.3d at 1153 (Gorsuch, J.,
    concurring) (“Trying to infer the intentions of an institution
    composed of 535 members is a notoriously doubtful business under
    the best of circumstances.”).
    114
    Antonin Scalia, Common-Law Courts in a Civil-Law System: The
    Role of United States Federal Courts in Interpreting the Constitution
    and Laws, in A MATTER OF INTERPRETATION: FEDERAL COURTS
    AND THE LAW 3, 17 (Amy Gutmann ed., 1997).
    115
    Id.
    116
    Cf. Public Health & Environmental Respondent-Intervenors’ Br.
    at 10-11.
    117
    Chevron, 
    467 U.S. at 842
    .
    37
    *   *    *
    This case touches on some of administrative law’s most
    consequential, unresolved issues. What is the reach of
    Massachusetts v. EPA? What is the meaning of a major
    question? What are the limits of congressional delegation?
    Each of those issues — and a dozen or two more — might
    have mattered if the EPA had relied on a section of the Clean
    Air Act other than § 111 to promulgate both rules at issue in
    this case. But a 1990 amendment to § 111 excluded a category
    of regulations from § 111’s scope. And because that category
    covers the regulations challenged today, those other legal
    questions are academic.
    Both houses of Congress voted that amendment — the
    House Amendment — into law. And as explained above, if it
    conflicts with the Senate-proposed amendment to § 111, the
    Senate Amendment was a drafter’s error.
    On the other hand, if the House and Senate Amendments
    can coexist, the House Amendment simply excludes from
    § 111’s scope a category of regulations in addition to the
    regulations excluded by the Senate Amendment.
    Either way, the law precludes what the House Amendment
    precludes. And the House Amendment precludes § 111
    regulations of coal-fired power plants already covered by
    § 112.
    Therefore, the EPA correctly repealed the 2015 Rule, but
    its replacement rule improperly applied § 111 to coal-fired
    power plants already regulated under § 112.
    38
    Those conclusions lead to this respectful concurrence in
    part, concurrence in the judgment in part, and dissent in part.118
    118
    The majority’s thoughtful opinion (I) describes this case’s
    regulatory and procedural history; (II) vacates the 2019 Rule; (III.A)
    rejects most of the Coal Petitioners’ arguments, including their
    contention that the EPA cannot use § 111 to regulate carbon
    emissions from power plants already regulated under § 112; (III.B)
    dismisses the Robinson Petitioners’ challenge for lack of standing;
    (IV) vacates the EPA’s implementing regulations for emission
    guidelines promulgated under § 111(d); (V) describes the remedy;
    and (VI) concludes. I concur in part of the judgment with respect to
    Part II, concur with respect to Part III.B, and concur in the judgment
    with respect to Part IV.
    

Document Info

Docket Number: 19-1140

Filed Date: 1/19/2021

Precedential Status: Precedential

Modified Date: 1/19/2021

Authorities (73)

environmental-defense-fund-inc-sierra-club-natural-resources-defense , 82 F.3d 451 ( 1996 )

Lockhart v. United States , 136 S. Ct. 958 ( 2016 )

american-trucking-associations-inc-v-environmental-protection-agency , 283 F.3d 355 ( 2002 )

St AZ v. Thompson, Tommy G. , 281 F.3d 248 ( 2002 )

Fed. Energy Regulatory Comm'n v. Elec. Power Supply Ass'n , 136 S. Ct. 760 ( 2016 )

Spokeo, Inc. v. Robins , 136 S. Ct. 1540 ( 2016 )

Immigration & Naturalization Service v. Chadha , 103 S. Ct. 2764 ( 1983 )

Weinberger v. Bentex Pharmaceuticals, Inc. , 93 S. Ct. 2488 ( 1973 )

Green v. Bock Laundry MacHine Co. , 109 S. Ct. 1981 ( 1989 )

General Motors Corp. v. United States , 110 S. Ct. 2528 ( 1990 )

Gregory v. Ashcroft , 111 S. Ct. 2395 ( 1991 )

United States National Bank v. Independent Insurance Agents ... , 113 S. Ct. 2173 ( 1993 )

At&T Corp. v. Iowa Utilities Board , 119 S. Ct. 721 ( 1999 )

North Dakota v. United States , 103 S. Ct. 1095 ( 1983 )

Five Flags Pipe Line Company v. Department of ... , 854 F.2d 1438 ( 1988 )

Barnhart v. Thomas , 124 S. Ct. 376 ( 2003 )

planned-parenthood-federation-of-america-inc-v-margaret-m-heckler , 712 F.2d 650 ( 1983 )

telecommunications-research-and-action-center-and-media-access-project-v , 801 F.2d 501 ( 1986 )

Whitman v. American Trucking Assns., Inc. , 121 S. Ct. 903 ( 2001 )

Talk America, Inc. v. Michigan Bell Telephone Co. , 131 S. Ct. 2254 ( 2011 )

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