Navajo Nation v. Usdoi ( 2022 )


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  •                 FOR PUBLICATION
    UNITED STATES COURT OF APPEALS
    FOR THE NINTH CIRCUIT
    NAVAJO NATION,                          No. 19-17088
    Plaintiff-Appellant,
    D.C. No.
    v.                     3:03-cv-00507-
    GMS
    U.S. DEPARTMENT OF THE INTERIOR;
    DEB HAALAND, Secretary of the
    Interior; UNITED STATES BUREAU OF       ORDER AND
    RECLAMATION; BUREAU OF INDIAN            AMENDED
    AFFAIRS,                                  OPINION
    Defendants-Appellees,
    STATE OF ARIZONA; CENTRAL
    ARIZONA WATER CONSERVATION
    DISTRICT; ARIZONA POWER
    AUTHORITY; SALT RIVER PROJECT
    AGRICULTURAL IMPROVEMENT AND
    POWER DISTRICT; SALT RIVER
    VALLEY WATER USERS’
    ASSOCIATION; IMPERIAL IRRIGATION
    DISTRICT; METROPOLITAN WATER
    DISTRICT OF SOUTHERN CALIFORNIA;
    COACHELLA VALLEY WATER
    DISTRICT; STATE OF NEVADA;
    COLORADO RIVER COMMISSION OF
    NEVADA; SOUTHERN NEVADA
    WATER AUTHORITY; STATE OF
    COLORADO,
    Intervenor-Defendants-Appellees.
    2                 NAVAJO NATION V. USDOI
    Appeal from the United States District Court
    for the District of Arizona
    G. Murray Snow, Chief District Judge, Presiding
    Argued and Submitted October 16, 2020
    Pasadena, California
    Filed April 28, 2021
    Amended February 17, 2022
    Before: Ronald M. Gould, Marsha S. Berzon, and
    Kenneth K. Lee, Circuit Judges.
    Order;
    Opinion by Judge Gould;
    Concurrence by Judge Lee
    SUMMARY *
    Water Rights / Tribal Matters
    The panel reversed the district court’s dismissal, based
    on lack of jurisdiction, of Navajo Nation’s breach of trust
    claim alleging that Federal Appellees failed to consider the
    Nation’s as-yet-undetermined water rights in managing the
    Colorado River.
    The district court held that any attempt by the Nation to
    amend its complaint was futile because the district court
    lacked jurisdiction to decide the breach of trust claim due to
    *
    This summary constitutes no part of the opinion of the court. It
    has been prepared by court staff for the convenience of the reader.
    NAVAJO NATION V. USDOI                      3
    the Supreme Court reserving jurisdiction over allocation of
    rights to the Colorado River in Arizona v. California
    (Arizona I), 
    373 U.S. 546
     (1963) (opinion); accord Arizona
    v. California (1964 Decree), 
    376 U.S. 340
    , 353 (1964)
    (decree).
    The panel held that the district court erred in dismissing
    the complaint because the amendment was not futile.
    Although the Supreme Court retained original jurisdiction
    over water rights claims to the Colorado River in Arizona I,
    the Nation’s complaint did not seek a judicial quantification
    of rights to the River, and therefore, the panel need not
    decide whether the Supreme Court’s retained jurisdiction
    was exclusive. The panel concluded it had jurisdiction to
    consider the Nation’s claim, and the district court erred in
    holding otherwise.
    The panel held, contrary to the Intervenors’ arguments
    on appeal, that the Nation’s claim was not barred by res
    judicata, despite the federal government’s representation of
    the Nation in Arizona I. The panel held that the Nation, here,
    asserted a different claim than the water rights claim the
    federal government could have asserted on the Nation’s
    behalf in Arizona I. The federal government’s fiduciary duty
    to the Nation was never at issue in Arizona I, and no final
    judgment was ever entered on the merits of any question
    concerning that subject.
    Finally, the panel held that the district court erred in
    denying the Nation’s motion to amend and in dismissing the
    Nation’s complaint, because the complaint properly stated a
    breach of trust claim premised on the Nation’s treaties with
    the United States and the Nation’s federally reserved Winters
    rights, especially when considered along with the Federal
    Appellees’ pervasive control over the Colorado River. At
    4                NAVAJO NATION V. USDOI
    this early stage of the litigation, the panel declined to address
    whether the Nation’s Winters rights included rights to the
    mainstream of the Colorado River or to any other specific
    water resources. The panel remanded to the district court
    with instructions to permit the Nation to amend its
    complaint.
    Judge Lee concurred. He wrote separately to emphasize
    that the Nation’s proposed injunctive relief should not and
    did not implicate the Supreme Court’s retained jurisdiction
    in the 1964 Decree.
    COUNSEL
    M. Kathryn Hoover (argued), Sacks Tierney P.A.,
    Scottsdale, Arizona; Stanley M. Pollack, Navajo Nation
    Department of Justice, Window Rock, Arizona; Alice E.
    Walker and Gregg H. DeBie, Meyer Walker Condon &
    Walker P.C., Boulder, Colorado; for Plaintiff-Appellant.
    John L. Smeltzer (argued), Mary Gabrielle Sprague, and
    Thomas Snodgrass, Attorneys; Todd Kim, Assistant
    Attorney General; Environment and Natural Resources
    Division, United States Department of Justice, Washington,
    D.C.; Robert Snow and Sarah Foley, Attorneys, Solicitor’s
    Office, United States Department of the Interior,
    Washington, D.C.; for Defendants-Appellees.
    Rita P. Maguire (argued), Rita P. Maguire PLLC, Phoenix,
    Arizona; Steven B. Abbott, Redwine and Sherrill LLP,
    Riverside, California; Kenneth C. Slowinski and Jennifer
    Heim, Arizona Department of Water Resources, Phoenix,
    Arizona; Marcia Scully and Catherine M. Stites,
    Metropolitan Water District of Southern California, Los
    NAVAJO NATION V. USDOI                     5
    Angeles, California; Charles T. DuMars, Law & Resource
    Planning Associates P.C., Albuquerque, New Mexico; John
    B. Weldon Jr. and Lisa M. McKnight, Salmon Lewis &
    Weldon P.L.C., Phoenix, Arizona; Stuart L. Somach and
    Robert B. Hoffman, Somach Simmons & Dunn APC,
    Sacramento, California; Jay M. Johnson, Central Arizona
    Water Conservation District, Phoenix, Arizona; Aaron Ford,
    Attorney General; Christine Guerci-Nyhus, Special Counsel
    to the Colorado River Commission of Nevada; State of
    Nevada and Colorado River Commission of Nevada, Las
    Vegas, Nevada; Gregory J. Walch, General Counsel,
    Southern Nevada Water Authority, Las Vegas, Nevada;
    Lauren J. Caster and Bradley J. Pew, Fennemore Craig P.C.,
    Phoenix, Arizona; Philip J Weiser, Attorney General; A.
    Lain Leoniak, First Assistant Attorney General; Office of the
    Attorney General, Denver, Colorado; for Intervenor-
    Defendants-Appellees.
    Monte Tyler Mills, Associate Professor and Director,
    Margery Hunter Brown Indian Law Clinic, Alexander
    Blewett III School of Law, University of Montana,
    Missoula, Montana, for Amici Curiae Law Professors.
    David L. Gover, Joe M. Tenorio, and Matthew Campbell,
    Native American Rights Fund, Boulder, Colorado; Daniel D.
    Lewerenz, Native American Rights Fund, Washington,
    D.C.; Derrick Beetso, National Congress of American
    Indians, Washington, D.C.; for Amicus Curiae NCAI Fund.
    6               NAVAJO NATION V. USDOI
    ORDER
    The opinion in the above-captioned matter filed on April
    28, 2021, and published at 
    996 F.3d 623
    , is amended as
    follows:
    At 996 F.3d at 629, delete 43 U.S.C. § 1521
    .>
    At 996 F.3d at 641, replace  with 
    The panel has voted to deny Intervenor-Appellees’
    petition for rehearing en banc (Dkt. 61), and to deny
    Defendant-Appellees’ petition for rehearing en banc
    (Dkt. 62). The full court has been advised of the petitions
    for rehearing en banc and no judge has requested a vote on
    whether to rehear either matter en banc. Fed. R. App. P. 35.
    The petitions for rehearing en banc are DENIED. No future
    petitions will be entertained.
    NAVAJO NATION V. USDOI                      7
    OPINION
    GOULD, Circuit Judge:
    In 2003, the Navajo Nation (the Nation) sued the
    Department of the Interior (Interior), the Secretary of the
    Interior (the Secretary), the Bureau of Reclamation, and the
    Bureau of Indian Affairs (collectively, the Federal
    Appellees), bringing claims under the National
    Environmental Policy Act (NEPA) and a breach of trust
    claim for failure to consider the Nation’s as-yet-
    undetermined water rights in managing the Colorado River.
    Several parties, including Arizona, Nevada, and various state
    water, irrigation, and agricultural districts and authorities
    (collectively, the Intervenors), intervened to protect their
    interests in the Colorado’s waters. In a prior appeal, we held
    that while the Nation lacked Article III standing to bring its
    NEPA claims, its breach of trust claim was not barred by
    sovereign immunity, and we remanded to the district court.
    Navajo Nation v. Dep’t of Interior (Navajo I), 
    876 F.3d 1144
    , 1174 (9th Cir. 2017). After re-considering the breach
    of trust claim, the district court dismissed the Nation’s
    complaint because of its view that any attempt to amend the
    complaint was futile. The district court held that it lacked
    jurisdiction to decide the claim because the Supreme Court
    reserved jurisdiction over allocation of rights to the Colorado
    River in Arizona v. California (Arizona I), 
    373 U.S. 546
    (1963) (opinion); accord Arizona v. California (1964
    Decree), 
    376 U.S. 340
    , 353 (1964) (decree). The district
    court also held that the Nation did not identify a specific
    treaty, statute, or regulation that imposed an enforceable
    trust duty on the federal government that could be vindicated
    in federal court. The Nation appealed.
    We conclude that the district court erred in dismissing
    the complaint because, in contrast to the district court’s
    8                NAVAJO NATION V. USDOI
    determination, the amendment was not futile. Although the
    Supreme Court retained original jurisdiction over water
    rights claims to the Colorado River in Arizona I, the Nation’s
    complaint does not seek a judicial quantification of rights to
    the River, so we need not decide whether the Supreme
    Court’s retained jurisdiction is exclusive. And contrary to
    the Intervenors’ arguments on appeal, the Nation’s claim is
    not barred by res judicata, despite the federal government’s
    representation of the Nation in Arizona I. Finally, the district
    court erred in denying the Nation’s motion to amend and in
    dismissing the Nation’s complaint, because the complaint
    properly stated a breach of trust claim premised on the
    Nation’s treaties with the United States and the Nation’s
    federally reserved Winters rights, especially when
    considered along with the Federal Appellees’ pervasive
    control over the Colorado River. We remand to the district
    court with instructions to permit the Nation to amend its
    complaint.
    I
    The Nation is a federally recognized Indian tribe that has
    signed two treaties with the United States. In ratifying the
    first treaty in 1849, the United States placed the Navajo
    people “under the exclusive jurisdiction and protection of the
    . . . United States,” providing “that they are now, and will
    forever remain, under the aforesaid jurisdiction and
    protection.” Treaty with the Navaho, 1849 art. I (Sep. 9,
    1849), 
    9 Stat. 974
    .           The Navajo Reservation (the
    “Reservation”) was established as the “permanent home” of
    the Nation by the 1868 Treaty between the United States of
    America and the Navajo Tribe of Indians, 1868 art. XIII
    (June 1, 1868), 
    15 Stat. 667
     (1868 Treaty). The Reservation
    was later expanded by executive orders and acts of Congress.
    NAVAJO NATION V. USDOI                      9
    The Reservation sprawls across Arizona, New Mexico,
    and Utah, and lies almost entirely within the drainage basin
    of the Colorado River. The Colorado River flows along and
    defines a significant part of the Reservation’s western
    border. Because much of the land in the Colorado River
    drainage basin is arid, competition for water from the
    Colorado River and its tributaries is fierce.
    To resolve disputes arising from water scarcity, rights to
    the Colorado River’s waters are allocated through a series of
    federal treaties, statutes, regulations, and common law
    rulings; Supreme Court decrees; and interstate compacts.
    Collectively, this legal regime is known as the “Law of the
    River.”
    A
    The Law of the River begins with the 1922 Colorado
    River Compact (1922 Compact), which split the Colorado
    River water equally between two groups of states: the
    “Upper Basin” states, consisting of Colorado, New Mexico,
    Utah, and Wyoming, and the “Lower Basin” states: Arizona,
    California, and Nevada. 1922 Compact art. II, reprinted in
    70 Cong. Rec. 324 (Dec. 10, 1928). Each group collectively
    received 7.5 million acre-feet per year (mafy) of water. 
    Id.
    art. III. The 1922 Compact did not, however, apportion the
    7.5 mafy among the individual states in either the Upper or
    Lower Basin. See 
    id.
     art. VIII. Nor did it “affect[] the
    obligations of the United States of America to Indian tribes.”
    
    Id.
     art. VII.
    Six years later, Congress conditionally approved the
    1922 Compact through the Boulder Canyon Project Act
    (BCPA). 
    43 U.S.C. § 617
     et seq. The BCPA allowed
    Interior to construct the Hoover Dam and a reservoir at Lake
    Mead. See 
    id.
     § 617. It empowered the Secretary to contract
    10                NAVAJO NATION V. USDOI
    for the storage and delivery of water in Lake Mead. See id.
    Finally, it authorized the Lower Basin States to negotiate a
    second compact dividing their 7.5 mafy share: 4.4 mafy to
    California, 2.8 to Arizona, and 0.3 to Nevada. See 43 U.S.C.
    § 617c(a).
    The 1922 Compact—including the second compact
    apportionment—was to take effect once all three Lower
    Basin states ratified it. See id. But Arizona, displeased with
    the Compact’s terms, failed to ratify it. So the issue of how
    to share the Lower Basin States’ apportionment went
    unresolved.      See Arizona I, 
    373 U.S. at
    561–62.
    Nonetheless, because six of the seven Basin states ratified
    the BCPA, the Secretary began contracting for water with
    the Lower Basin states. 1 
    Id. at 562
    .
    In 1952, still dissatisfied with its allotment, Arizona sued
    California in the Supreme Court, invoking the Court’s
    original jurisdiction. 
    Id.
     at 550–51. Nevada and other Basin
    States intervened, as did the United States. 
    Id. at 551
    .
    In proceedings before a Special Master, the United States
    asserted claims to various water sources in the Colorado
    River Basin on behalf of twenty-five tribes. But the United
    States only asserted claims to the Colorado River
    mainstream on behalf of five tribes, and the Nation was not
    among them. Instead, the United States at that time limited
    the Nation’s claim to the Little Colorado River, one of the
    tributaries in the Colorado River system. Navajo I, 876 F.3d
    at 1156 n.13. The Nation, along with other tribes, sought the
    1
    The BCPA lowered the 1922 Compact’s ratification threshold: six
    states would suffice for ratification as long as California was among
    them and committed to a ceiling on its apportionment. See 43 U.S.C.
    § 617c(a).
    NAVAJO NATION V. USDOI                    11
    appointment of a Special Assistant Attorney General to
    represent their interests, but their request was denied. The
    Nation also sought to intervene in proceedings before the
    Special Master, but its motion to intervene was denied at the
    United States’ urging. See Response of the United States to
    the Motion on Behalf of the Navajo Tribe of Indians for
    Leave to Intervene, Arizona I, 
    373 U.S. 546
     (No. 8,
    Original).
    The Supreme Court issued its decree in 1964. See 1964
    Decree, 
    376 U.S. 340
    . The Court excluded the Little
    Colorado River—and therefore the Nation’s claim—from
    the adjudication, along with other tributaries in the river
    system. See 
    id.
     art. VIII(B), 
    376 U.S. at
    352–53. It also
    affirmed the apportionment of the first 7.5 mafy among the
    Lower Basin States as specified in the BCPA and the
    accompanying second compact. 
    Id.
     art. II(B), 
    376 U.S. at
    341–42. The Decree stated that in years where there is less
    than 7.5 million acre-feet available in the Lower Basin,
    Interior must first “provide[] for satisfaction of present
    perfected rights in the order of their priority dates without
    regard to state lines.” 
    Id.
     art. II(B)(3), 
    376 U.S. at 342
    .
    Then, “after consultation with the parties to major delivery
    contracts and such representatives as the respective States
    may designate, [the Secretary] may apportion the amount
    remaining available for consumptive use in such manner as
    is consistent with” the BCPA, the 1964 Decree, and other
    applicable federal statutes. 
    Id.
    The 1964 Decree also determined the Winters rights of
    the five tribes for whom the federal government asserted
    federally reserved rights. See 
    id.
     at 344–45. Under the
    Winters doctrine, “when the Federal Government withdraws
    its land from the public domain” for the purpose of
    establishing an Indian reservation, “the Government, by
    12                  NAVAJO NATION V. USDOI
    implication, reserves appurtenant water then unappropriated
    to the extent needed to accomplish the purpose of the
    reservation.” Cappaert v. United States, 
    426 U.S. 128
    , 138
    (1976); see Winters v. United States, 
    207 U.S. 564
    , 576
    (1908).
    Water is essential to life on earth, see Sandra Alters,
    Biology: Understanding Life 39 (3d ed. 2000), and it is
    particularly essential for healthy human societies. 2 Further,
    beyond the general import of water for societies, in the
    specific case of the Navajo Nation, news reports have
    indicated that the Nation’s shortage of water have in part
    caused exacerbation of the risks from COVID-19. Many
    homes on the Reservation lack running water, making it
    difficult for tribal members to wash their hands regularly.
    See Ian Lovett et. al, Covid-19 Stalks Large Families in
    Rural America, Wall St. J. (June 7, 2020),
    https://www.wsj.com/articles/covid-19-households-spread-
    coronavirus-families-navajo-california-second-wave-
    11591553896. The Nation has as a result been particularly
    affected by the current pandemic, with a death rate
    2
    It is by no accident that many of the world’s ancient civilizations
    were born in places such as the Tigris-Euphrates delta, and the valleys
    of the Nile, Indus, and Yellow Rivers. Pierre-Louis Viollet, Water
    Engineering in Ancient Civilizations9 (Forrest M. Holly trans., 2017).
    The engineers of classical Rome built a vast network of aqueducts that,
    at its peak, spanned over 250 miles in length. During the Last Gothic
    War, King Vitiges led an army of Ostrogoths to the gates of Rome itself.
    The invaders encircled the city and blocked off the aqueducts, keenly
    aware that the Romans could not survive a prolonged siege without
    access to water. See Peter J. Aicher, Guide to the Aqueducts of Ancient
    Rome 6 (1995). In more recent times, Israel, faced with a paucity of
    water, has developed techniques for managing wastewater and pioneered
    desalinization techniques. In 2011, Israel desalinated 296 million cubic
    meters (MCM) of water out of sea water, and forty-five MCM out of
    brackish water. Water Policy in Israel 5 (Nir Becker ed., 2013).
    NAVAJO NATION V. USDOI                            13
    significantly higher than that of many other parts of the
    country. See 
    id.
     3
    In Winters, the United States, acting as trustee of the Fort
    Belknap Tribe, sought to enjoin upstream diversions on
    Montana’s Milk River from interfering with the Fort
    Belknap Reservation’s downstream diversions. See Winters,
    
    207 U.S. at 565
    . Although the 1888 treaty that established
    the Reservation made no express provision for tribal water
    rights to the Milk River, the United States maintained that
    the water had been impliedly reserved to fulfill the purpose
    of the reservation as a “permanent home and abiding place”
    for the Fort Belknap Tribe. 
    Id.
     The Court agreed, noting
    that the Reservation lands “were arid, and, without
    irrigation, were practically valueless.” 
    Id. at 576
    . The Court
    applied the Indian canons of construction, under which
    ambiguities in agreements and treaties with tribes “will be
    resolved from the standpoint of the Indians,” and held that
    the Tribe was entitled to federally reserved rights to the Milk
    River. Id.; see 
    id.
     at 576–77.
    Winters set a “solid foundation” for later decisions that
    reaffirmed the scope of Indian reserved water rights. Robert
    T. Anderson, Indian Water Rights and the Federal Trust
    Responsibility, 46 Nat. Res. J. 399, 414 (2006). Subsequent
    decisions have established that these rights are determined
    by federal, not state law. See 1 Cohen’s Handbook of
    Federal Indian Law § 19.03 (Nell Jessup Newton ed., 2019)
    3
    The vast majority of deaths on the Reservation due to COVID-19
    are among people aged sixty and older, including the hataałii, traditional
    medicine men and women entrusted with preserving the Nation’s
    cultural heritage. Jack Healy, Tribal Elders Are Dying From the
    Pandemic, Causing a Cultural Crisis for American Indians, N.Y. Times
    (Jan. 12, 2021), https://www.nytimes.com/2021/01/12/us/tribal-elders-
    native-americans-coronavirus.html.
    14               NAVAJO NATION V. USDOI
    (Cohen’s Handbook). Moreover, tribal water rights may
    trump water rights of state users, even when those users have
    been drawing from the water source for a longer time. See
    id.
    In awarding five tribes federally reserved water rights,
    the Arizona Court reaffirmed the Winters doctrine, noting
    that “most of the [reservation] lands were of the desert
    kind—hot, scorching sands—and . . . water from the
    [Colorado] river would be essential to the life of the Indian
    people and to the animals they hunted and the crops they
    raised.” Arizona I, 
    373 U.S. at 599
    . These five tribes
    received rights to water commensurate with the “practically
    irrigable acreage” within each tribe’s reservation. 
    Id. at 600
    ;
    see 1964 Decree art. II(D), 
    376 U.S. at
    343–45. However,
    the Supreme Court declined to adjudicate the claims of the
    twenty other tribes for whom the United States asserted
    claims—including the Nation’s. Arizona I, 
    373 U.S. at 595
    (“While the [Special] Master passed upon some of these
    claims, he declined to reach others, particularly those
    relating to tributaries. We approve his decision as to which
    claims required adjudication . . . .”).
    B
    Federal Appellees, through Interior and its Secretary,
    exercise pervasive control over the Colorado River pursuant
    to the BCPA, the 1964 Decree, and other components of the
    Law of the River. See 
    id. at 593
    . The Secretary has
    discretion to apportion shortfalls in years of shortage, see 
    id.
    at 593–94, and also has the authority to determine whether
    there is a surplus or shortage of water each year, see 1964
    Decree, art. II(B)(2)–(3), 
    376 U.S. at 342
    .
    In 1968, Congress enacted the Colorado River Basin
    Project Act (the “Basin Act”), which requires Interior to
    NAVAJO NATION V. USDOI                     15
    manage Lake Mead, Lake Powell, and related facilities in
    coordination and under long-range operating criteria.
    
    43 U.S.C. § 1552
    (a). Each year, Interior must determine
    whether there will be enough water to satisfy the 7.5 mafy
    budgeted among the Lower Basin states, and whether and
    how much “surplus” water will be available. See 
    73 Fed. Reg. 19,873
    , 19,875 (Apr. 11, 2008). In 2001 and 2007,
    Interior adopted “surplus” and “shortage” guidelines to
    clarify how it determines whether a particular year was a
    “shortage” or “surplus” year. See 
    66 Fed. Reg. 7772
     (Jan.
    25, 2001); 
    73 Fed. Reg. 19,873
     (Apr. 11, 2008).
    Before adopting the shortage guidelines, the Secretary
    published a draft environmental impact statement (EIS)
    discussing Indian Trust Assets, which are defined as legal
    interests in assets held in trust by the federal government for
    federally recognized tribes. See Final Environmental Impact
    Statement, Colorado River Interim Guidelines for Lower
    Basin Shortages and Coordinated Operations for Lake
    Powell and Lake Mead (Shortage Guidelines FEIS) 3-87
    (Oct. 2007). The EIS acknowledges that under the Winters
    doctrine, the federal government impliedly “reserved water
    in an amount necessary to fulfill the purposes of an Indian
    reservation” for the Navajo Reservation. Id. at 3-96. The
    EIS also states that while “[t]he existence of a federally
    reserved right for the Navajo Nation to mainstream
    Colorado River has not been judicially determined at this
    time[, u]nquantified water rights of the Navajo Nation are
    considered an [Indian Trust Asset].” Id.
    II
    The Nation filed a complaint against Federal Appellees
    under the Administrative Procedure Act (APA), 
    5 U.S.C. §§ 701
    –706, challenging the 2001 Surplus Guidelines.
    Navajo I, 876 F.3d at 1159. The Nation alleged that Federal
    16              NAVAJO NATION V. USDOI
    Appellees violated the National Environmental Policy Act
    (NEPA), 
    42 U.S.C. § 4321
     et seq., and breached its trust
    obligations based on the Federal Appellees’ management of
    the Colorado River without considering or meeting the
    Nation’s unquantified federal reserved water rights and
    unmet water needs, Navajo I, 876 F.3d at 1159. Several
    parties—Arizona, Nevada, and various state water,
    irrigation, and agricultural districts and authorities
    (collectively, “Intervenors”)—intervened to protect their
    interests in the Colorado’s waters. Id. The district court
    dismissed the complaint, holding that the Nation lacked
    standing to bring its NEPA claims and that its breach of trust
    claim was barred by sovereign immunity.
    On appeal, we agreed with the district court that the
    Nation lacked standing to bring its NEPA claims but
    reversed and remanded on the breach of trust claim. Id.
    at 1174. We held that the waiver of sovereign immunity in
    § 702 of the APA “applie[d] squarely to the Nation’s breach
    of trust claim.” Id. at 1173. Because the breach of trust
    claim was not barred by sovereign immunity, we instructed
    the district court to fully consider the claim on its merits,
    “after entertaining any request to amend the claim more fully
    to flesh it out.” Id.
    On remand, the Nation twice moved for leave to file an
    amended complaint.        The Proposed Third Amended
    Complaint (TAC) alleged that the Federal Appellees have
    failed to (1) “determine the quantities and sources of water
    required to make the Navajo Nation a permanent homeland
    for the Navajo People,” and (2) “protect the sovereign
    interests of the Navajo Nation by securing an adequate water
    supply to meet those homeland purposes.” The Intervenors
    opposed both motions to amend, arguing that because the
    United States could have asserted the Nation’s claim to the
    NAVAJO NATION V. USDOI                       17
    mainstream of the Colorado River in the Arizona v.
    California litigation and the rights to the River were fully
    adjudicated in that action, the Nation’s claim was barred by
    res judicata.
    The district court denied both motions to amend and
    dismissed the Nation’s complaint with prejudice. The
    district court held that although a general trust relationship
    exists between the United States and the tribes, the Nation
    failed to identify a specific trust-creating statute, regulation,
    or other form of positive law that the federal government
    violated. And though the Nation argued that such a specific
    trust obligation is created under the Winters doctrine, the
    district court held that a determination of whether Winters
    rights attached to the mainstream of the Colorado River was
    jurisdictionally barred by the Supreme Court’s reservation
    of jurisdiction in Arizona v. California. We conclude that
    the Nation’s claim does not implicate the Court’s reservation
    of jurisdiction, and that it therefore was error for the district
    court not to grapple with the scope of Winters rights
    available to the Nation in connection with its current
    requests.
    The district court further reasoned that even if it could
    decide the breach of trust claim, Winters rights alone do not
    give rise to specific and enforceable trust duties on the
    federal government. The district court also held that none of
    the treaties, statutes, and regulations that the Nation cited in
    support of its trust claim were “specific . . . trust-creating
    statute[s] or regulation[s] that the Government violated.”
    Finally, the district court held that the Nation could not
    allege a common law cause of action for breach of trust that
    is “wholly separate from any statutorily granted right.”
    We disagree with the district court as to the role of
    Winters rights in establishing enforceable trust duties.
    18               NAVAJO NATION V. USDOI
    Winters rights are necessarily implied in each treaty in which
    the government took land from Native Americans and
    established reservations that were to be permanent homes for
    them. That was the case with the Nation’s reservation.
    Federal Appellees have an irreversible and dramatically
    important trust duty requiring them to ensure adequate water
    for the health and safety of the Navajo Nation’s inhabitants
    in their permanent home reservation.
    Because the district court concluded that the Nation’s
    attempts to amend its complaint were futile, the district court
    denied the motion to amend and dismissed the complaint.
    The Nation timely appealed. Although the district court did
    not decide the res judicata issue in dismissing the Nation’s
    complaint, Intervenors assert that res judicata defense on
    appeal.
    This appeal presents three issues. First, we determine
    whether the Nation’s breach of trust claim falls within the
    Supreme Court’s reserved jurisdiction in Arizona v.
    California. If it does, we decide whether that jurisdiction is
    not only reserved, but also exclusive. Second, we determine
    whether the Nation’s claim is barred by res judicata. Third,
    we decide whether the Nation could properly state a claim
    for breach of trust such that amendment was not futile.
    III
    We review a district court’s denial of a motion to amend
    a complaint for abuse of discretion. Wheeler v. City of Santa
    Clara, 
    894 F.3d 1046
    , 1051 (9th Cir. 2018). “A district
    court’s exercise of discretion based on an erroneous
    interpretation of the law constitutes an abuse of discretion.”
    Ahlmeyer v. Nev. Sys. of Higher Educ., 
    555 F.3d 1051
    , 1055
    (9th Cir. 2009). Moreover, “[d]ismissal without leave to
    amend is improper unless it is clear, upon de novo review,
    NAVAJO NATION V. USDOI                     19
    that the complaint could not be saved by any amendment.”
    Polich v. Burlington N., Inc., 
    942 F.2d 1467
    , 1472 (9th Cir.
    1991). Finally, we review a district court’s decision to
    dismiss for lack of subject matter jurisdiction de novo.
    DaVinci Aircraft, Inc. v. United States, 
    926 F.3d 1117
    , 1122
    (9th Cir. 2019).
    IV
    A
    We begin with the jurisdictional question. The district
    court determined it could not decide the Nation’s breach of
    trust claim because it falls within the Supreme Court’s
    reserved jurisdiction under Article IX of the 1964 Decree.
    Article IX provides that:
    Any of the parties may apply at the foot of
    this decree for its amendment or for further
    relief. The Court retains jurisdiction of this
    suit for the purpose of any order, direction, or
    modification of the decree, or any
    supplementary decree, that may at any time
    be deemed proper in relation to the subject
    matter in controversy.
    1964 Decree, art. IX, 
    376 U.S. at 353
    . The parties and the
    district court assumed that this provision reserves the
    Supreme Court’s exclusive jurisdiction over—and strips
    lower courts of jurisdiction to determine—whether the
    Nation has water rights to a specific allocation from the
    mainstream of the Colorado River. But in attempting to
    avoid Article IX’s jurisdictional bar, the Nation represents
    that it does not seek a judicial determination of its rights to
    the Colorado. The Nation argues that it merely seeks an
    injunction ordering the Federal Appellees to investigate the
    20               NAVAJO NATION V. USDOI
    Nation’s needs for water, to develop a plan to meet those
    needs, and to exercise its authority over the management of
    the Colorado River consistent with that plan. Under this
    reading of the Nation’s claim, the district court only had to
    consider whether the Nation needs water to fulfill the
    promise of establishing the Navajo Reservation as a
    homeland for the Nation’s people.
    We agree with the Nation’s characterization of its claim.
    A plain reading of the Nation’s complaint makes clear that it
    does not seek a quantification of its rights in the Colorado
    River. The Nation seeks an injunction “[r]equiring the
    Federal Appellees . . . (1) to determine the extent to which
    the Navajo Nation requires water . . . (2) to develop a plan to
    secure the water needed; (3) to exercise their authorities,
    including those for the management of the Colorado River,
    in a manner that does not interfere with the plan to secure the
    water needed . . . and (4) to require the Federal Appellees to
    analyze their actions . . . and adopt appropriate mitigation
    measures to offset any adverse effects from those actions.”
    Granting this scope of relief would not require a judicial
    quantification of the Nation’s rights to water from the River.
    Nor would it require any modification of the Arizona Decree.
    Furthermore, Article VIII(C) of the Decree provides that the
    Decree does not affect “[t]he rights or priorities, except as
    specific provision is made herein, of any Indian
    Reservation.” 1964 Decree, 
    376 U.S. at 353
    . As discussed
    infra, the Nation’s claim is not determined by any specific
    provision in the 1964 Decree, as none addresses the Navajo
    Nation’s water rights. The Nation’s breach of trust claim
    thus falls outside the scope of the Decree, and our
    jurisdiction is proper.
    Because the Nation does not seek a judicial
    determination of its rights to the waters of the Colorado
    NAVAJO NATION V. USDOI                      21
    River, we need not resolve the scope of the Supreme Court’s
    reserved jurisdiction under Article IX. But we note that the
    Supreme Court’s own interpretation of the Decree does not
    expressly state whether Article IX’s reserved jurisdiction is
    exclusive. In the sequel to Arizona I, the federal government
    sought to increase the water allotments for the five tribes that
    were awarded federally reserved water rights in the original
    litigation, arguing that the earlier calculations of the
    practicably irrigable acreage within the reservations were
    inaccurate. Arizona v. California (Arizona II), 
    460 U.S. 605
    ,
    608 (1983). The Court denied the request, and stated that if
    not for Article IX, the Court would have been barred by res
    judicata from re-opening the matter. 
    Id.
     at 617–18. The
    Court explained that Article IX was “mainly a safety net
    added to retain jurisdiction and to ensure that we had not, by
    virtue of res judicata, precluded ourselves from adjusting the
    Decree in light of unforeseeable changes in circumstances.”
    
    Id. at 622
    . Because the Supreme Court is best positioned to
    interpret its own Decree, we defer to the interpretation it laid
    out in Arizona II and understand Article IX primarily as an
    authorization of jurisdiction, rather than a limitation on it.
    Because the Nation neither seeks modification of the
    Decree nor seeks to relitigate any issues resolved in the
    Arizona cases, see infra, however, we need not resolve the
    scope of the Supreme Court’s jurisdiction under Article IX.
    We have jurisdiction to consider the Nation’s claim, and the
    district court erred in holding otherwise.
    B
    Having established that we have jurisdiction, we turn to
    the Intervenors’ argument that res judicata bars the Nation’s
    claim. Intervenors argue that the Nation’s breach of trust
    claim is barred by res judicata because the Nation
    effectively seeks a judicial determination of its rights to the
    22               NAVAJO NATION V. USDOI
    Colorado River, which is a claim that the federal government
    could have asserted on the Nation’s behalf in Arizona I, but
    did not. We reject the Intervenors’ argument because the
    Nation’s claim is not barred by res judicata.
    In Nevada v. United States, 
    463 U.S. 110
     (1982), the
    Supreme Court held that res judicata barred the federal
    government from seeking additional water rights for the
    Pyramid Lake Tribe beyond the rights the tribe obtained in
    previous water rights litigation, id. at 113, 145. The Nevada
    Court considered “first if the cause of action which the
    Government now seeks to assert is the same cause of action
    that was asserted” in previous litigation, and then “whether
    the parties in the instant proceeding are identical to or in
    privity with” the parties in the previous litigation. Id. at 130
    (internal quotation marks omitted). The Court held that the
    federal government, in a decades-long adjudication that
    began in 1913, sought to “assert . . . the Reservation’s full
    water rights.” Id. at 132. Because Nevada involved the same
    parties “asserting the same reserved right” as that
    adjudicated by the previous litigation, id. at 134, the later
    claim was barred.
    In this case, by contrast, the Nation asserts a different
    claim than the water rights claim the federal government
    could have asserted on the Nation’s behalf in Arizona I. The
    Nation’s claim, properly understood, is an action for breach
    of trust—not a claim seeking judicial quantification of its
    water rights. The federal government’s fiduciary duty to the
    Navajo Nation was never at issue in Arizona v. California,
    and no final judgment was ever entered on the merits of any
    question concerning that subject. Cf. Nevada, 463 U.S.
    at 129–30. As the Decree does not affect “[t]he rights or
    priorities” of Indian Reservation beyond those specifically
    enumerated, 1964 Decree, 
    376 U.S. at 353
    , the federal
    NAVAJO NATION V. USDOI                     23
    government’s fiduciary duty to the Nation remains unaltered
    by the Arizona litigation.
    The Nation’s breach of trust claim is not barred by res
    judicata.
    C
    1
    Finally, we address whether the Nation’s attempts to
    amend its complaint to plead their substantive breach of trust
    claim were futile. The Federal Appellees and the Intervenors
    argue that the district court correctly denied the Nation’s
    motion for leave to amend its complaint, because it could not
    point to any specific treaty provision, statute, or regulation
    that imposed a trust obligation on the Federal Appellees. We
    disagree and hold that the district court should have allowed
    the Nation to amend its complaint.
    This circuit first considered the requirements a tribe must
    meet to bring a breach of trust action for non-monetary relief
    in Morongo Band of Mission Indians v. F.A.A., 
    161 F.3d 569
    (9th Cir. 1998). There, the Morongo Tribe challenged a
    Federal Aviation Administration (FAA) proposal that would
    have increased air traffic over reservation lands. 
    Id.
     at 572–
    73. The Tribe sought non-monetary relief under the APA,
    alleging violations of various statutes and FAA regulations.
    
    Id. at 572
    . We held that “unless there is a specific duty that
    has been placed on the government with respect to Indians,
    this responsibility is discharged by the agency’s compliance
    with general regulations and statutes not specifically aimed
    at protecting Indian tribes.” 
    Id. at 574
    .
    We addressed this issue again in Gros Ventre Tribe v.
    United States, 
    469 F.3d 801
     (9th Cir. 2006). There, the Gros
    24               NAVAJO NATION V. USDOI
    Ventre Tribe alleged that the federal government breached
    its trust obligations “by approving, permitting, and failing to
    reclaim” two cyanide heap-leach gold mines upriver from
    the Tribe’s reservation. 
    Id. at 806
    . The panel explained that
    “an Indian tribe cannot force the government to take a
    specific action unless a treaty, statute or agreement imposes,
    expressly or by implication, that duty.” 
    Id. at 810
     (emphasis
    added) (quoting Shoshone-Bannock Tribes v. Reno, 
    56 F.3d 1476
    , 1482 (D.C. Cir. 1995)). In holding that the Tribe
    failed to identify a treaty, statute, or regulation that would
    create an enforceable trust duty, we observed that the Tribe’s
    treaties with the federal government “at most . . . merely
    recognize[d] a general or limited trust obligation to protect
    the Indians against depredations on Reservation lands.” Id.
    at 812 (emphasis added). Because the Tribe sought an
    injunction requiring the federal government to “manage
    resources that exist off of the Reservation,” we held that no
    treaty provision imposed an enforceable trust duty that could
    be vindicated through injunctive relief. Id. at 812–13
    (emphasis added).
    Morongo and Gros Ventre establish the governing
    standard here. Although Federal Appellees rely on another
    strain of cases concerning the need to identify specific
    statutory bases for obtaining monetary relief under the
    Tucker Act, 
    28 U.S.C. § 1491
    , those cases are not apposite.
    The fiduciary claim in this case is one for injunctive
    relief under § 702 of the APA. In United States v. Mitchell
    (Mitchell I), 
    445 U.S. 535
     (1980), individual members of the
    Quinault Tribe sued the federal government through the
    Tucker Act, 
    28 U.S.C. § 1491
    , over alleged mismanagement
    of timber resources on their allotted reservation lands,
    
    445 U.S. at 537, 539
    . The timber was managed by the
    Secretary of Interior under the General Allotment Act
    NAVAJO NATION V. USDOI                   25
    (GAA). 
    Id. at 537
    . The Supreme Court rejected the tribal
    allottees’ argument that the GAA imposed enforceable trust
    duties on the federal government to manage tribal timber
    resources in a fiduciary capacity. 
    Id. at 546
    . The Court
    explained that when Congress enacted the GAA, it intended
    that the federal government hold the land in trust “not
    because it wished the Government to control use of the land
    and be subject to money damages for breaches of fiduciary
    duty, but simply because it wished to prevent alienation of
    the land and to ensure that allottees would be immune from
    the state taxation.” 
    Id. at 544
    . The Court remanded the case
    to the Court of Claims to consider whether the federal
    government could be held liable for breach of trust based on
    any other statutes. 
    Id. at 546
    .
    On remand, the Court of Claims held that the
    government was subject to suit for money damages based on
    various statutes and regulations detailing the federal
    government’s responsibilities in managing the tribal timber
    resources. United States v. Mitchell (Mitchell II), 
    463 U.S. 206
    , 211 (1983). The Supreme Court affirmed, holding that
    the regulations and statutes created an enforceable trust
    obligation because they accorded the Secretary a “pervasive
    role in the sales of timber from Indian lands.” 
    Id. at 219
    .
    The Court observed that a substantive right to sue under the
    Tucker Act “must be found in some other source of law, such
    as ‘the Constitution, or any Act of Congress, or any
    regulation of an executive department.’” 
    Id. at 216
     (quoting
    
    28 U.S.C. § 1491
    ). “[T]he claimant must demonstrate that
    the source of substantive law he relies upon ‘can fairly be
    interpreted as mandating compensation by the Federal
    Government for the damages sustained.’” 
    Id.
     at 216–17
    (quoting United States v. Testan, 
    424 U.S. 392
    , 400 (1976)).
    26               NAVAJO NATION V. USDOI
    These Supreme Court decisions concerned suits brought
    for money damages under the Tucker Act, 
    28 U.S.C. § 1491
    ,
    and the Indian Tucker Act, 
    28 U.S.C. § 1505
    . But this case
    involves a claim for injunctive relief brought under § 702 of
    the APA, so we are not bound by those decisions.
    A more recent decision, United States v. Jicarilla,
    
    564 U.S. 162
     (2011), concerned a breach of trust claim in a
    discovery context and imported requirements similar to
    those stated in the Tucker Act and Indian Tucker Act cases.
    In Jicarilla, the Court decided whether the Jicarilla Apache
    Nation (the “Tribe”) could assert the “fiduciary exception”
    to the attorney-client privilege in a suit against the federal
    government, 
    id. at 165
    . At first, the Tribe sued the
    government for breach of trust, seeking monetary damages
    for alleged mismanagement of tribal funds. 
    Id. at 166
    . Then
    the parties participated in alternative dispute resolution,
    wherein the government refused to produce certain
    documents, claiming the attorney-client privilege. 
    Id.
     So
    the Tribe moved to compel production of those documents.
    
    Id. at 167
    . It asserted the “fiduciary exception” to the
    attorney-client privilege, which states that a trustee cannot
    assert the privilege against a beneficiary after obtaining legal
    advice on how to execute its fiduciary obligations. 
    Id.
    The Court held that the Tribe could not compel the
    federal government to produce privileged documents in
    discovery based on the fiduciary exception, because it failed
    to “point to a right conferred by statute or regulation in order
    to obtain otherwise privileged information from the
    Government against its wishes.” 
    Id. at 178
    . In doing so, the
    Court observed that it had previously “found that particular
    ‘statutes and regulations . . . clearly establish fiduciary
    obligations of the Government’ in some areas.” 
    Id. at 177
    (ellipsis in original) (quoting Mitchell II, 
    463 U.S. at 226
    ).
    NAVAJO NATION V. USDOI                       27
    But the Court also explained that “[o]nce federal law
    imposes such duties, the common law ‘could play a role’” in
    defining the scope of those duties. 
    Id.
     (quoting United States
    v. Navajo Nation, 
    556 U.S. 287
    , 301 (2009)). Again,
    Jicarilla was at bottom a suit for monetary relief. Its ruling
    must be understood against that background.
    2
    Federal Appellees contend that under these precedents,
    the Nation has failed to state a breach of trust claim because
    it cannot point to any treaty, statute, or regulation that
    imposes an affirmative trust duty on the federal government
    to ensure that the Nation has an adequate water supply. We
    disagree.
    Here, the injunctive relief the Nation seeks would not
    require the federal government to manage off-reservation
    resources.    Instead, the Nation seeks an injunction
    compelling the Secretary to determine the extent to which
    the Reservation requires water from sources other than the
    Little Colorado River to fulfill the Reservation’s purpose of
    establishing a permanent homeland for the Nation. The
    mainstream of the Colorado River is appurtenant to the
    Nation and defines a significant segment of the
    Reservation’s western boundary.
    Moreover, neither Morongo nor Gros Ventre nor
    Jicarilla involved claims to vindicate Winters rights, which
    provide the foundation of the Nation’s claim here. Unlike
    the plaintiffs in those cases, the Nation, in pointing to its
    reserved water rights, has identified specific treaty, statutory,
    and regulatory provisions that impose fiduciary obligations
    on Federal Appellees—namely, those provisions of the
    Nation’s various treaties and related statutes and executive
    orders that establish the Navajo Reservation and, under the
    28              NAVAJO NATION V. USDOI
    long-established Winters doctrine, give rise to implied water
    rights to make the reservation viable.
    Under Winters, the federal government “reserve[d]
    appurtenant water then unappropriated to the extent needed
    to accomplish” the purpose of establishing the Reservation
    as a permanent homeland for the Navajo people. Navajo I,
    876 F.3d at 1155 (quoting Cappaert, 
    426 U.S. at 138
    ). In
    Colville Confederated Tribes v. Walton, 
    647 F.2d 42
     (9th
    Cir. 1981), we noted that while “[t]he specific purposes of
    an Indian reservation . . . were often unarticulated,” “[t]he
    general purpose, to provide a home for the Indians, is a broad
    one and must be liberally construed,” 
    id. at 47
    . It is clear
    that the Reservation cannot exist as a viable homeland for
    the Nation without an adequate water supply. As the Court
    observed in Arizona I:
    Most of the land in [the reservations
    appurtenant to the Colorado River] is and
    always has been arid. If the water necessary
    to sustain life is to be had, it must come from
    the Colorado River or its tributaries. It can
    be said without overstatement that when the
    Indians were put on these reservations they
    were not considered to be located in the most
    desirable area of the Nation. It is impossible
    to believe that when Congress created the
    great Colorado River Indian Reservation and
    when the Executive Department of this
    Nation created the other reservations they
    were unaware that most of the lands were of
    the desert kind—hot, scorching sands—and
    that water from the river would be essential
    to the life of the Indian people and to the
    NAVAJO NATION V. USDOI                             29
    animals they hunted and the crops they
    raised.
    
    373 U.S. at
    598–99.
    We stress that Winters rights are long-established and
    clearly qualify as rights “by implication” under a treaty.
    Gros Ventre, 
    469 F.3d at 810
     (quoting Shoshone-Bannock,
    
    56 F.3d at 1482
    ). Those necessarily implied rights are just
    as important as express ones. It is not our province to modify
    the Supreme Court’s definitive law establishing water rights
    as contained in treaties establishing Native American
    reservations, whether express or not. None of the twists and
    turns in the responsible federal agencies’ and courts’
    historical treatment of Indian law has brought the Winters
    declaration of necessarily implied water rights into question.
    We hold in particular that, under Winters, Federal
    Appellees have a duty to protect the Nation’s water supply
    that arises, in part, from specific provisions in the 1868
    Treaty that contemplated farming by the members of the
    Reservation. The Treaty provides that individual members
    of the Nation may select plots of land if they “desire to
    commence farming.” 1868 Treaty, art. V. Tribal members
    who took up farming would be entitled to “seeds and
    agricultural implements” to help make this transition. 
    Id.
     art.
    VII. The Treaty’s farming-related provisions, which sought
    to encourage the Nation’s transition to an agrarian lifestyle,
    would have been meaningless unless the Nation had
    sufficient access to water. 4 Indeed, in Winters itself, the
    4
    In the Nation’s first motion for leave to file a third amended
    complaint, the Nation sought to add, in addition to its breach of fiduciary
    duty claim, a claim for breach of the 1849 and 1868 Treaties, but later
    omitted that claim from its renewed motion. On remand, the district
    30                NAVAJO NATION V. USDOI
    Court explained that at the time the Fort Belknap Tribe
    signed its treaty with the federal government, it was the
    government’s policy to change the Tribe’s “habits and
    wants” to those of “a pastoral and civilized people.”
    Winters, 
    207 U.S. at 576
    . We do not pass judgment on the
    wisdom of such a policy, nor on the merits of particular
    allegations that may be offered relating to agrarian rights, but
    it is clear that the Winters Court based its holding in large
    part on the fact that without water, the reservation lands
    could not support an agrarian lifestyle in accordance with
    government policy. See 
    id.
     (“The lands were arid, and,
    without irrigation, were practically valueless.”).
    That the farming provisions in the 1868 Treaty may
    serve as the “specific statute” that satisfies Jicarilla,
    Morongo, and Gros Ventre is consistent with more general
    principles concerning the interpretation of treaties between
    the United States and Indian tribes. The Supreme Court has
    explained: “A treaty, including one between the United
    States and an Indian tribe, is essentially a contract between
    two sovereign nations.” Washington v. Wash. State Com.
    Passenger Fishing Vessel Ass’n, 
    443 U.S. 658
    , 675,
    modified sub nom. Washington v. United States, 
    444 U.S. 816
     (1979) (citing Lone Wolf v. Hitchcock, 
    187 U.S. 553
    (1979)). We have inferred a promise of water rights into
    treaties that contained no explicit reservation of those rights.
    See, e.g., Arizona I, 
    373 U.S. at 599
    ; Agua Caliente Band of
    Cahuilla Indians v. Coachella Valley Water Dist., 
    849 F.3d 1262
    , 1268 (9th Cir. 2017).
    We did so in United States v. Adair, 
    723 F.2d 1394
     (9th
    Cir. 1983), for example, where the Klamath Tribe’s treaty
    court is instructed that the Nation should be permitted to amend its
    complaint in this respect if it seeks to do so.
    NAVAJO NATION V. USDOI                     31
    with the United States merely preserved the right to “hunt,
    fish, and gather on their reservation,” Id. at 1398. We
    recognized that a main purpose of the treaty was to “secure
    to the Tribe a continuation of its traditional hunting and
    fishing lifestyle.” Id. at 1409. We reasoned that this purpose
    would have been defeated unless the Klamath Tribe had the
    right to enjoy and use water sufficient to ensure an adequate
    supply of game and fish. See id. at 1411. Although the
    claimed water rights at issue in that case were “essentially
    nonconsumptive in nature,” id. at 1418, Adair stands for the
    broader proposition that we may read water rights into a
    treaty where those rights are necessary to fulfill the treaty’s
    primary purpose. See United States v. Washington, 
    853 F.3d 946
    , 965 (9th Cir. 2017) (“Thus, even if Governor Stevens
    had made no explicit promise, we would infer, as in Winters
    and Adair, a promise to ‘support the purpose’ of the
    Treaties.”).
    Interior’s documents also demonstrate that the Federal
    Appellees have acknowledged their trust responsibilities to
    protect the Nation’s Winters rights. For example, the final
    EIS relating to Interior’s shortage guidelines acknowledges
    that the federal government impliedly “reserved water in an
    amount necessary to fulfill the purposes of” the Navajo
    Reservation. Shortage Guidelines FEIS, 3-96. The EIS also
    states that the Nation’s unquantified water rights are
    considered an Indian Trust Asset, which Interior recognizes
    as interests that the federal government holds in trust for
    recognized Indian tribes, and that the federal government
    must protect. 
    Id.
    The Nation’s breach of trust claim is also strengthened
    and reinforced by the Secretary’s pervasive control over the
    Colorado River. The BCPA, which requires the United
    States and all Colorado River users to “observe and be
    32               NAVAJO NATION V. USDOI
    subject to and controlled by” the 1922 Compact, apportioned
    the Colorado River’s waters among the Lower Basin states.
    43 U.S.C. § 617g(a). But within the general allocation of
    water that the 1922 Compact entails, the Secretary has
    pervasive authority “both to carry out the allocation of the
    waters of the main Colorado River among the Lower Basin
    States and to decide which users within each State would get
    water.” Arizona I, 
    373 U.S. at 580
    .
    In this respect, the Supreme Court’s reasoning in
    Mitchell II is pertinent: just as the statutes and regulations in
    that case gave the Secretary a “pervasive role in the sales of
    timber from Indian lands,” 
    463 U.S. at 219
    , so too do the
    BCPA and other components of the Law of the River confer
    broad authority upon the Secretary to manage and contract
    for Colorado River water, see, e.g., BCPA, 43 U.S.C. § 617d
    (“No person shall have or be entitled to have the use for any
    purpose of the water stored as aforesaid except by contract
    made as herein stated.”). This pervasive control over the
    Colorado River, coupled with the Nation’s Winters rights,
    outlines the scope of Federal Appellees’ trust duties.
    Our holding is consistent with the Supreme Court’s
    decision in United States v. Navajo Nation. Although the
    Court there held that “[t]he Federal Government’s liability
    cannot be premised on control alone,” 
    556 U.S. at 301
    , the
    Court also explained that once a plaintiff identifies a specific
    duty-imposing treaty, statute, or regulation, “then trust
    principles (including any such principles premised on
    ‘control’) could play a role in ‘inferring that the trust
    obligation [is] enforceable by damages.’” 
    Id.
     (quoting
    United States v. White Mountain Apache Tribe, 
    537 U.S. 465
    , 473 (2003)). The Nation—which in any case does not
    here seek money damages—has identified a specific duty-
    imposing treaty, as we have explained.
    NAVAJO NATION V. USDOI                     33
    To summarize: We hold that the Nation has successfully
    identified specific treaty, statutory, and regulatory
    provisions that, taken together, anchor its breach of trust
    claim. First, we have the implied treaty rights recognized in
    Winters, which in itself gives the Tribe the right to proceed
    on a breach of trust claim here; second, the 1868 Treaty,
    which recognizes the Nation’s right to farm Reservation
    lands and, under Adair, gives rise to an implied right to the
    water necessary to do so; third, the BCPA and other statutes
    that grant the Secretary authority to exercise pervasive
    control over the Colorado River; and fourth and finally, the
    Nation has pointed to Interior regulations and documents in
    which Federal Appellees have undertaken to protect Indian
    Trust Assets, including the Nation’s as-yet-unquantified
    Winters rights.
    Having established that a fiduciary duty exists, we hold
    that common-law sources of the trust doctrine and the
    control the Secretary exercises over the Colorado River
    firmly establish the Federal Appellees’ duty to protect and
    preserve the Nation’s right to water. Under Winters, when
    the federal government took the Reservation into trust, it
    “reserve[d] appurtenant water then unappropriated to the
    extent needed to accomplish” that purpose. Navajo I,
    876 F.3d at 1155 (quoting Cappaert, 
    426 U.S. at 138
    ).
    These rights are recognized as reserved by treaty, applying
    the canon that in “agreements and treaties with the Indians,
    ambiguities occurring will be resolved from the standpoint
    of the Indians.” Winters, 
    207 U.S. at 576
    ; see Washington,
    853 F.3d at 965. Though water rights are not expressly
    stated in the Nation’s treaties with the United States, the
    Winters rights that attach to the Reservation are sufficiently
    well-established to create an implied fiduciary obligation on
    the Federal Appellees. See Gros Ventre, 
    469 F.3d at 810
    (noting that a specific duty can be imposed by “a treaty,
    34                 NAVAJO NATION V. USDOI
    statute or agreement . . . expressly or by implication.”)
    (quoting Shoshone-Bannock, 56 F.2d at 1482).
    We recognize that no court has yet quantified the
    Nation’s Winters rights. But the fault for the exceedingly
    long delay in that respect, if any, lies with Federal Appellees.
    As trustee, the federal government has the power to not only
    bring water rights claims on behalf of the tribes, but also to
    bind them in litigation. See Nevada, 
    463 U.S. at 135
    . When
    the Nation tried to intervene in Arizona v. California, the
    federal government opposed the Nation’s motion. And in
    the more than half of a century since the Supreme Court
    issued its 1964 Decree, the Nation has never had its Winters
    rights adjudicated or quantified by any court. 5 This result is
    but one example of what a commentator has described as the
    federal government’s failure “to secure, protect, and develop
    adequate water supplies for many Indian tribes.” Cohen's
    Handbook § 19.06. Indeed, “[i]n the history of the United
    States Government’s treatment of Indian tribes, its failure to
    protect Indian water rights for use on the reservations it set
    aside for them is one of the sorrier chapters.” 6 Id. (citing
    National Water Comm’n, Water Policies for the Future:
    Final Report to the President and to the Congress of the
    United States, 474–75 (1973)); see also Anderson, supra, at
    400.
    5
    The Nation is actively seeking water from various sources in other
    litigation. See generally Navajo I, 876 F.3d at 1156 n.14.
    6
    Perhaps recognizing this failure, some members of Congress have
    proposed legislation that would empower the Administrator of the
    Environmental Protection Agency to “give priority to projects that
    respond to emergency situations where a lack of access to clean drinking
    water threatens the health of Tribal populations” in the Columbia River
    Basin. S. 421, 117th Cong. § 2 (2021).
    NAVAJO NATION V. USDOI                     35
    The Supreme Court could not have intended to hamstring
    the Winters doctrine—which has remained good law for
    more than one hundred years—by preventing tribes from
    seeking vindication of their water rights by the federal
    government when the government has failed to discharge its
    duties as trustee. Such a perverse reading of the Court’s
    precedents would render ineffectual the federal
    government’s promise to “charge[] itself with moral
    obligations of the highest responsibility and trust,” Seminole
    Nation v. United States, 
    316 U.S. 286
    , 297 (1942), by
    ensuring that the tribes of this country can make their
    reservation lands livable. This principle takes on even more
    importance in an era in which the COVID-19 pandemic
    renders reservation lands more dangerous to tribal
    members—particularly when they lack adequate water for
    health and safety purposes.
    The Nation’s attempts to amend its complaint were not
    futile. The Nation can state a cognizable claim for breach of
    trust because it has identified specific regulations and treaty
    provisions that can “fairly be interpreted,” Mitchell II,
    
    463 U.S. at 218
    , as establishing Federal Appellees’ fiduciary
    obligations to ensure that the Nation’s Reservation has the
    water it needs to exist as a viable homeland for the Navajo
    people.
    At this early stage of litigation, we decline to address
    whether the Nation’s Winters rights include rights to the
    mainstream of the Colorado River or to any other specific
    water sources. We hold only that the Nation may properly
    base its breach of trust claim on water rights derived from its
    treaties with the United States under Winters, and so may
    amend its complaint to so allege.
    36                 NAVAJO NATION V. USDOI
    V
    Because the district court’s denial of the Nation’s motion
    for leave to amend and subsequent dismissal of the Nation’s
    complaint were based on legal errors, the court abused its
    discretion. Applying the correct legal principles, we hold
    that the Nation’s attempts to amend its complaint were not
    futile. We reverse the district court’s dismissal of the
    Nation’s complaint and remand to the district court with
    instructions to permit amendment to the complaint
    consistent with this opinion. 7
    REVERSED AND REMANDED.
    LEE, Circuit Judge, concurring:
    I write separately to emphasize that the Nation’s
    proposed injunctive relief should not and does not implicate
    the Supreme Court’s retained jurisdiction in Arizona v.
    California (1964 Decree), 
    376 U.S. 340
    , 353 (1964).
    When the Supreme Court first adjudicated the rights to
    the Colorado River, it issued a Decree listing the Indian
    tribes and other entities holding present perfected rights to
    the mainstream. 
    Id.
     at 344–46. Article IX of the Decree
    7
    As the concurrence recognizes, we need not and do not decide
    whether the Supreme Court’s retained jurisdiction in the 1964 Decree is
    exclusive. That is because the Nation’s claim does not seek a
    quantification of any rights it may have to the Colorado River
    mainstream. If, however, Federal Appellees later determine that they
    cannot meet their trust obligation to provide adequate water for the
    Nation unless the jurisdictional question is resolved, then they can
    petition the Supreme Court for modification of the 1964 Decree.
    NAVAJO NATION V. USDOI                      37
    “retain[ed] jurisdiction . . . for the purpose of any order,
    direction, or modification of the decree, or any
    supplementary decree . . .” 
    Id. at 353
    . Since then, there have
    been several iterations of the Arizona v. California litigation,
    but none has explicitly addressed whether Article IX
    reserves exclusive jurisdiction for adjudication of rights to
    the mainstream. See, e.g., Arizona v. California (Arizona II),
    
    460 U.S. 605
    , 622 (1983).
    In this case, the Nation seeks additional water for its
    Reservation, and both the parties and the district court
    considered whether the Supreme Court’s retained
    jurisdiction applied. But our decision does not answer that
    question, as the Nation’s Proposed Third Amended
    Complaint (“TAC”) does not, on its face, actually seek rights
    to the mainstream.
    The Nation’s TAC seeks injunctive relief requiring, in
    part, that the Federal Defendants “determine the extent to
    which the Navajo Nation requires water from sources other
    than the Little Colorado River to enable its Reservation to
    serve as a permanent homeland for the Navajo Nation and
    its members” and “develop a plan to secure the water
    needed.” The Nation asserts, and our decision affirms, that
    this proposed injunction does not ask the district court to
    quantify any rights that the Nation may have to the Colorado
    River mainstream. This narrow construction of the proposed
    relief is imperative, as it allows the Nation to pursue its
    claims without raising the separate and more complex issue
    of the Supreme Court’s retained jurisdiction.
    Thus, on remand and in all future proceedings, the
    TAC’s proposed injunctive relief should not be construed as
    implicitly authorizing a reassessment of the rights to the
    Colorado River mainstream. In other words, the requested
    relief that the Federal Defendants develop a plan to meet the
    38               NAVAJO NATION V. USDOI
    Nation’s water needs cannot be used as a backdoor attempt
    to allocate the rights to the mainstream. If such rights are to
    be reassessed, that action may be taken only after resolving
    the jurisdictional question raised by Article IX of the 1964
    Decree.