Ali Hamza Ahmad al Bahlul v. United States , 767 F.3d 1 ( 2014 )


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  •  United States Court of Appeals
    FOR THE DISTRICT OF COLUMBIA CIRCUIT
    Argued September 30, 2013              Decided July 14, 2014
    No. 11-1324
    ALI HAMZA AHMAD SULIMAN AL BAHLUL,
    PETITIONER
    v.
    UNITED STATES OF AMERICA,
    RESPONDENT
    On Petition for Rehearing En Banc
    Michel Paradis, Counsel, Office of the Chief Defense
    Counsel, argued the cause for the petitioner. Mary R.
    McCormick and Todd E. Pierce, Counsel, were on brief.
    David S. Weissbrodt and William J. Aceves were on brief
    for amicus curiae International Law Scholars in support of the
    petitioner.
    Agnieszka Fryszman was on brief for amicus curiae
    National Institute of Military Justice in support of the
    petitioner.
    McKenzie A. Livingston was on brief for amici curiae
    Robert D. Steele and other Former Members of the
    Intelligence Community in support of the petitioner.
    2
    John S. Summers and Michael J. Newman were on brief
    for amici curiae Professors David Glazier and Gary Solis in
    support of the petitioner.
    Sarah H. Paoletti was on brief for amici curiae
    Historians, Political Scientists and Constitutional Law
    Scholars in support of the petitioner.
    Jeffrey T. Renz was on brief for amici curiae First
    Amendment Scholars and Historians and the Montana Pardon
    Project in support of the petitioner.
    Elizabeth B. Wydra was on brief for amicus curiae
    Constitutional Accountability Center in support of the
    petitioner.
    Ian H. Gershengorn, Attorney, U.S. Department of
    Justice, argued the cause for the respondent. Steven M.
    Dunne, Chief Attorney, and John F. De Pue, Attorney, were
    on brief. Jeffrey M. Smith, Trial Attorney, U.S. Department
    of Justice, and Francis A. Gilligan and Edward S. White,
    Attorneys, Office of Military Commissions, entered
    appearances.
    James A. Schoettler Jr. was on brief for amici curiae
    Former Government Officials, Former Military Lawyers and
    Scholars of National Security Law in support of respondent.
    Cory L. Andrews and Richard A. Samp were on brief for
    amici curiae Washington Legal Foundation et al. in support of
    the respondent.
    Before: GARLAND, Chief Judge, and HENDERSON,
    ROGERS, TATEL, BROWN, GRIFFITH and KAVANAUGH, Circuit
    Judges.
    3
    Opinion for the court filed by Circuit Judge HENDERSON.
    Concurring opinion filed by Circuit Judge HENDERSON.
    Opinion concurring in the judgment in part and
    dissenting filed by Circuit Judge ROGERS.
    Opinion concurring in the judgment in part and
    dissenting in part filed by Circuit Judge BROWN.
    Opinion concurring in the judgment in part and
    dissenting in part filed by Circuit Judge KAVANAUGH.
    KAREN LECRAFT HENDERSON, Circuit Judge: Ali Hamza
    Ahmad Suliman al Bahlul (Bahlul) served as a personal
    assistant to Osama bin Laden, produced propaganda videos
    for al Qaeda and assisted with preparations for the attacks of
    September 11, 2001 that killed thousands of Americans.
    Three months after 9/11, Bahlul was captured in Pakistan and
    transferred to the United States Naval Base at Guantanamo
    Bay, Cuba. Military prosecutors charged him with three
    crimes: conspiracy to commit war crimes, providing material
    support for terrorism and solicitation of others to commit war
    crimes. A military commission convicted him of all three
    crimes and sentenced him to life imprisonment. The United
    States Court of Military Commission Review (CMCR)
    affirmed his conviction and sentence. Bahlul appeals. For the
    reasons that follow, we reject Bahlul’s ex post facto challenge
    to his conspiracy conviction and remand that conviction to the
    original panel of this Court for it to dispose of several
    remaining issues. In addition, we vacate his material support
    and solicitation convictions.
    4
    I. Background
    Bahlul is a native of Yemen. In the late 1990s, he
    traveled to Afghanistan to join al Qaeda. He completed
    military-like training while staying at an al Qaeda guesthouse
    and eventually met and pledged an oath of loyalty (“bayat”) to
    bin Laden. Bin Laden assigned Bahlul to work in al Qaeda’s
    media office.
    On October 12, 2000, al Qaeda suicide bombers attacked
    the U.S.S. Cole, killing 17 American servicemen and
    wounding 39 others. Bin Laden later instructed Bahlul to
    create a video celebrating the attack for use as a recruiting
    tool. The video Bahlul produced (and bin Laden edited)
    includes footage of the attack, calls for jihad against the
    United States and propaganda blaming “Western infidels” and
    complicit Middle Eastern regimes for Muslim suffering.
    Bahlul considered it one of the best propaganda videos al
    Qaeda had produced and it has been translated into several
    languages and widely distributed.
    Bin Laden then appointed Bahlul as his personal assistant
    and secretary for public relations. Bahlul arranged the loyalty
    oaths of two of the 9/11 hijackers, Mohamed Atta and Ziad al
    Jarrah, and prepared their “martyr wills”—propaganda
    declarations documenting al Qaeda’s role in the attacks.
    Bahlul claims he sought to participate in the 9/11 attacks
    himself but bin Laden refused because he considered his
    media man too important to lose. In the days preceding 9/11,
    Bahlul assembled al Qaeda’s media equipment and evacuated
    al Qaeda’s Kandahar headquarters with bin Laden and other
    senior al Qaeda leaders. They traveled to a remote region of
    Afghanistan where, on September 11, 2001, they heard
    reports of the day’s attacks via a radio operated by Bahlul.
    5
    Bin Laden subsequently asked Bahlul to research the
    economic effects of the attacks and report his findings.
    In the following weeks, Bahlul fled to Pakistan. He was
    captured there in December 2001 and turned over to U.S.
    forces. In 2002, he was transferred to the U.S. Naval Base at
    Guantanamo Bay, Cuba, where he has since been detained as
    an enemy combatant pursuant to the 2001 Authorization for
    Use of Military Force (AUMF). See Pub. L. No. 107-40,
    § 2(a), 
    115 Stat. 224
    , 224; Hamdi v. Rumsfeld, 
    542 U.S. 507
    ,
    518, 521 (2004) (plurality). Two months after 9/11, President
    Bush invoked the AUMF and Article 21 of the Uniform Code
    of Military Justice (UCMJ), 
    10 U.S.C. § 821
     (hereinafter
    “section 821”), to establish military commissions to try
    “member[s] of . . . al Qaida” and others who “engaged in,
    aided or abetted, or conspired to commit, acts of international
    terrorism, or acts in preparation therefor.” See Detention,
    Treatment, and Trial of Certain Non-Citizens in the War
    Against Terrorism, 
    66 Fed. Reg. 57,833
     (Nov. 13, 2001). In
    2003, the President designated Bahlul eligible for trial by
    military commission and in 2004 military prosecutors charged
    him with conspiracy to commit war crimes.
    Bahlul’s prosecution was stayed pending the outcome of
    another detainee’s challenge to the lawfulness of his trial by
    military commission. In Hamdan v. Rumsfeld, the United
    States Supreme Court held that the military commission
    procedures then in place contravened certain constraints
    imposed by the UCMJ and the four Geneva Conventions
    signed in 1949. 
    548 U.S. 557
    , 613–35 (2006). In response to
    the Hamdan decision, the Congress enacted the Military
    Commissions Act of 2006 (2006 MCA), Pub. L. No. 109-336,
    
    120 Stat. 2600
    , which amended the statutory procedures
    governing military commissions to cure the flaws identified in
    Hamdan. The 2006 MCA specifically enumerated 30 war
    6
    crimes triable by military commission, see 10 U.S.C. §§ 950t–
    950v (2006),1 and conferred jurisdiction on military
    commissions to try “any offense made punishable by this
    chapter or the law of war when committed by an alien
    unlawful enemy combatant before, on, or after September 11,
    2001,” id. § 948d(a).
    The Supreme Court has long recognized that unlawful
    enemy combatants may be prosecuted by military commission
    for their war crimes. See Hamdan, 
    548 U.S. at
    592–93;
    Hamdi, 
    542 U.S. at 518
    ; In re Yamashita, 
    327 U.S. 1
    , 7–8, 11
    (1946); Ex parte Quirin, 
    317 U.S. 1
    , 28, 31 (1942). There are
    three traditional bases for military commission jurisdiction:
    military government, martial law and the law of war. See
    Hamdan, 
    548 U.S. at
    595–98 (plurality opinion); see also 
    id. at 683
     (Thomas, J., dissenting). First, military commissions
    may try ordinary crimes—e.g., manslaughter or robbery—and
    violations of military orders committed by both soldiers and
    civilians in territories under U.S. military government. 
    Id.
     at
    595–96. Second, military commissions may try ordinary
    crimes and violations of military orders committed by soldiers
    and civilians in territory under martial law—as much of our
    country was during the Civil War. See 
    id. at 595
    ; WILLIAM
    WINTHROP, MILITARY LAW AND PRECEDENTS 832–34 (rev. 2d
    ed. 1920). Third, and “utterly different” from the first two
    categories, military commissions may try offenses against the
    law of war. Hamdan, 
    548 U.S. at 596
     (plurality opinion)
    (citation omitted). It is undisputed that the commission that
    tried Bahlul is of the third type: a law-of-war military
    1
    The Military Commissions Act of 2009 rewrote the 2006
    MCA but left it substantively unaltered as relevant here. See
    National Defense Authorization Act for Fiscal Year 2010, Pub. L.
    No. 111-84, §§ 1801–07, 
    123 Stat. 2190
    , 2574–2614 (codified at 10
    U.S.C. §§ 948a–950t (Supp. III 2010)). Unless otherwise noted, we
    refer to the 2006 MCA.
    7
    commission. A military commission convened pursuant to
    the 2006 MCA must be composed of at least five “members,”
    who are qualified active duty officers of the armed forces and
    play a role similar to a petit jury. 10 U.S.C. §§ 948i, 948m.
    A military judge presides over the trial. Id. § 948j.
    In 2008, military prosecutors amended the charges
    against Bahlul to allege three of the offenses enumerated in
    the 2006 MCA based on the conduct summarized above—
    conspiracy to commit war crimes, providing material support
    for terrorism and solicitation of others to commit war crimes.
    See id. §§ 950u, 950v(b)(25), 950v(b)(28) (2006). The
    conspiracy and solicitation charges alleged seven object
    crimes proscribed by the 2006 MCA: murder of protected
    persons, attacking civilians, attacking civilian objects, murder
    in violation of the law of war, destruction of property in
    violation of the law of war, terrorism and providing material
    support for terrorism. See id. § 950v(b)(1)–(3), (15)–(16),
    (24)–(25). Bahlul admitted all of the factual allegations
    against him, with the exception of the allegation that he had
    armed himself with a suicide belt to protect bin Laden. He
    nevertheless pleaded not guilty to the charged offenses
    because he denied the legitimacy of the military commission
    and sought to absent himself from the proceedings as a
    boycott. He objected to representation by appointed defense
    counsel and expressed a desire to proceed pro se, although his
    attempts to absent himself from the proceedings at times
    complicated matters and forced defense counsel to stand in
    for Bahlul and carry out his instructions not to present a
    defense. Bahlul waived all pretrial motions, asked no
    questions during voir dire, made no objections to prosecution
    evidence, presented no defense and declined to make opening
    and closing arguments.
    8
    The military commission convicted Bahlul of all three
    offenses. Using a detailed findings worksheet, it found that
    Bahlul conspired to commit and solicited each of the seven
    alleged object offenses and that Bahlul committed ten of the
    eleven alleged overt acts. See Petitioner’s Appendix (App.)
    132–33.2      The commission sentenced him to life
    imprisonment and the convening authority, Susan J.
    2
    The military commission specifically found that Bahlul
    committed the following overt acts: (1) traveled to Afghanistan
    with the purpose and intent of joining al Qaeda; (2) met with Saif al
    Adl, the head of the al Qaeda Security Committee, as a step toward
    joining al Qaeda; (3) underwent military-type training at an al
    Qaeda sponsored training camp located in Afghanistan; (4) pledged
    fealty or “bayat” to the leader of al Qaeda, Osama bin Laden, joined
    al Qaeda and provided personal services in support of al Qaeda; (5)
    prepared and assisted in the preparation of various propaganda
    products, including the video “The Destruction of the American
    Destroyer U.S.S. Cole,” to solicit material support for al Qaeda, to
    recruit to and indoctrinate personnel about the organization and
    objectives of al Qaeda and to solicit, incite and advise persons to
    commit terrorism; (6) acted as personal secretary and media
    secretary of bin Laden in support of al Qaeda; (7) arranged for
    Muhammed Atta and Ziad al Jarrah to pledge fealty or “bayat” to
    bin Laden; (8) prepared the propaganda declarations styled as
    martyr wills of Atta and al Jarrah in preparation for the acts of
    terrorism perpetrated by Atta, al Jarrah and others at various
    locations in the United States on September 11, 2001; (9) at the
    direction of bin Laden, researched the economic effect of the 9/11
    attacks on the United States and provided the results of that
    research to bin Laden; and (10) operated and maintained data
    processing equipment and media communications equipment for
    the benefit of bin Laden and other members of the al Qaeda
    leadership. App. 132–33; see also id. at 122–23 (charging
    document).
    9
    Crawford,3 approved the findings and sentence. The CMCR
    affirmed Bahlul’s conviction and sentence in a 112-page
    opinion. See United States v. Bahlul, 
    820 F. Supp. 2d 1141
    (2011). Bahlul then appealed to this Court.
    While Bahlul’s appeal was pending, this Court held that
    the 2006 MCA “does not authorize retroactive prosecution for
    conduct committed before enactment of that Act unless the
    conduct was already prohibited under existing U.S. law as a
    war crime triable by military commission.” Hamdan v.
    United States (Hamdan II), 
    696 F.3d 1238
    , 1248 (D.C. Cir.
    2012) (emphasis in original). The Court declared that
    providing material support for terrorism—the only charge at
    issue in that appeal—was not a pre-existing war crime triable
    by military commission; it therefore vacated Hamdan’s
    conviction on that offense. 
    Id.
     at 1248–53. The Government
    subsequently conceded that Hamdan II’s reasoning required
    vacatur of all three of Bahlul’s convictions. Based on that
    concession, a panel of this Court vacated the convictions.
    Order, Bahlul v. United States, No. 11-1324, 
    2013 WL 297726
     (D.C. Cir. Jan. 25, 2013). We subsequently granted
    the Government’s petition for rehearing en banc.
    3
    Under the 2006 MCA, a military commission “may be
    convened by the Secretary of Defense or by any officer or official
    of the United States designated by the Secretary for that purpose.”
    10 U.S.C. § 948h. Crawford, a former judge of the United States
    Court of Appeals for the Armed Forces, was so designated by the
    Defense Secretary. The convening authority refers the charges
    against the accused for trial by military commission, details the
    members of the commission and approves or disapproves the
    findings and sentence of the commission. Id. §§ 948i(b), 950b; cf.
    Hamdan, 
    548 U.S. at
    647–49 (Kennedy, J., concurring) (explaining
    role of convening authority under UCMJ).
    10
    II. Standard of Review
    Bahlul argues that the 2006 MCA must be construed to
    make triable by military commission only those crimes that
    were recognized under the international law of war when
    committed. He further contends that, if the 2006 MCA
    authorizes retroactive prosecution of new law-of-war offenses
    by military commission, his convictions violate the Ex Post
    Facto Clause. Bahlul made neither of these arguments before
    the military commission.
    “ ‘No procedural principle is more familiar to this Court
    than that a constitutional right,’ or a right of any other sort,
    ‘may be forfeited in criminal as well as civil cases by the
    failure to make timely assertion of the right before a tribunal
    having jurisdiction to determine it.’ ” United States v. Olano,
    
    507 U.S. 725
    , 731 (1993) (quoting Yakus v. United States,
    
    321 U.S. 414
    , 444 (1944)). This fundamental principle of
    appellate review generally bars a party who failed to preserve
    an argument in a lower tribunal from raising it on appeal
    absent plain error or exceptional circumstances. See United
    States v. Atkinson, 
    297 U.S. 157
    , 159 (1936); Salazar ex rel.
    Salazar v. Dist. of Columbia, 
    602 F.3d 431
    , 437 (D.C. Cir.
    2010).
    To preserve error for appellate review, an appellant must
    interpose a “timely” objection, United States v. Simpson, 
    430 F.3d 1177
    , 1183 (D.C. Cir. 2005), and “state the specific
    ground for [the] objection,” United States v. Boyd, 
    54 F.3d 868
    , 872 (D.C. Cir. 1995). Although he need not “cite the
    particular case that supports his position,” United States v.
    Rashad, 
    396 F.3d 398
    , 401 (D.C. Cir. 2005), he must state the
    ground for his objection “with sufficient precision to indicate
    distinctly [his] thesis,” Miller v. Avirom, 
    384 F.2d 319
    , 322
    (D.C. Cir. 1967). Thus, “[a]n objection is not properly raised
    11
    if it is couched in terms too general to have alerted the trial
    court to the substance of the petitioner’s point.” United States
    v. Breedlove, 
    204 F.3d 267
    , 270 (D.C. Cir. 2000); see also
    Noonan v. Caledonia Gold Min. Co., 
    121 U.S. 393
    , 400
    (1887) (“The rule is universal, that where an objection is so
    general as not to indicate the specific grounds upon which it is
    made, it is unavailing on appeal, unless it be of such a
    character that it could not have been obviated at the trial.”).
    The contemporaneous-objection rule is not mere
    “obeisance to ritual.” Miller, 
    384 F.2d at 322
    . It serves two
    purposes. First, the rule promotes judicial efficiency by
    giving the trial tribunal the opportunity to quickly and
    efficiently resolve errors that would otherwise require
    burdensome and unnecessary appellate review and remand.
    See Puckett v. United States, 
    556 U.S. 129
    , 134 (2009).
    Second, the rule discourages the intentional withholding of an
    objection by a party to be raised on appeal only if he loses at
    trial. See id.; see also Wainwright v. Sykes, 
    433 U.S. 72
    , 89
    (1977); Hormel v. Helvering, 
    312 U.S. 552
    , 556 (1941);
    United States v. Socony-Vacuum Oil Co., 
    310 U.S. 150
    , 238–
    39 (1940) (citing Crumpton v. United States, 
    138 U.S. 361
    ,
    364 (1891)).
    To mitigate the sometimes harsh results of the forfeiture
    rule in criminal cases, the Congress authorizes the court of
    appeals to exercise its discretion to notice and correct a
    certain type of forfeited error: “plain error.” FED. R. CRIM. P.
    52(b); see United States v. Young, 
    470 U.S. 1
    , 15 (1985); see
    also 10 U.S.C. § 950a(a) (Supp. III 2010) (Military
    Commissions Act of 2009 review provision specifying that
    only errors that “materially prejudice[] the substantial rights
    12
    of the accused” may be corrected).4 A plain error is “[1] an
    ‘error’ [2] that is ‘plain’ and [3] that ‘affect[s] substantial
    rights.’ ” Olano, 
    507 U.S. at 732
     (quoting FED. R. CRIM P.
    52(b)) (final alteration in original). “If all three conditions are
    met, an appellate court may then exercise its discretion to
    notice a forfeited error, but only if (4) the error seriously
    affects the fairness, integrity, or public reputation of judicial
    proceedings.” Johnson v. United States, 
    520 U.S. 461
    , 467
    (1997) (quotation marks and brackets omitted). Plain-error
    review, however, is “highly circumscribed.” United States v.
    Brinson-Scott, 
    714 F.3d 616
    , 625 (D.C. Cir. 2013); see also
    Puckett, 
    556 U.S. at 134
     (“Meeting all four prongs is difficult,
    as it should be.” (quotation marks omitted)); Young, 
    470 U.S. at 15
     (“[T]he plain-error exception to the contemporaneous-
    objection rule is to be used sparingly, solely in those
    circumstances in which a miscarriage of justice would
    otherwise result.” (quotation marks omitted)). “There is good
    reason for this; anyone familiar with the work of courts
    understands that errors are a constant in the trial process, that
    most do not much matter, and that a reflexive inclination by
    appellate courts to reverse because of unpreserved error
    would be fatal” to the policies furthered by the
    contemporaneous-objection rule. Puckett, 
    556 U.S. at 134
    (quotation marks omitted). We therefore must guard against
    “unwarranted extension of this exacting definition of plain
    error.” Young, 
    470 U.S. at 15
    .5
    4
    We need not decide whether Rule 52(b) applies directly to
    this proceeding because plain-error review is appropriate whether
    or not Rule 52(b) directly governs. See Salazar, 
    602 F.3d at 437
    .
    5
    The Government argued for plain-error review before the
    CMCR, in its original brief to a panel of this Court and in its brief
    to the en banc court. See Bahlul, 
    820 F. Supp. 2d at
    1256–58; Br.
    of the United States 65, Bahlul v. United States, No. 11-1324 (D.C.
    Cir. May 16, 2012) (Panel Br.); Br. of the United States 63, Bahlul
    13
    Applying these principles here, we conclude that Bahlul
    forfeited the arguments he now raises. He flatly refused to
    participate in the military commission proceedings and
    instructed his trial counsel not to present a substantive
    defense. Although he objected to the commission’s authority
    to try him, his objection was couched entirely in political and
    religious terms. He disclaimed guilt and contended that “what
    [he] did was not a crime.” Trial Tr. 175. But context makes
    clear that Bahlul argued that his acts were not criminal
    because they were inspired by religious fervor. See 
    id.
     at
    175–76. After claiming that the United States had “put on the
    side[] the meaningless American laws” and “legislated new
    laws” for “the planet Earth,” he explained that he “believe[s]
    that no one has the right in the land to set laws for the people,
    the right of legislating laws[] is absolutely to Allah, the All
    Mighty.” 
    Id.
     at 23–24. Bahlul did ask a “legal question”
    about whether the “law here by you stems from the action,
    before action, or post action,” id. at 104, but the military
    judge could not ascertain what Bahlul was asking and Bahlul
    did not elaborate. Bahlul’s objection to the commission’s
    authority was unquestionably “too general to have alerted the
    trial court to the substance of [his] point.” United States v.
    Bolla, 
    346 F.3d 1148
    , 1152 (D.C. Cir. 2003) (Roberts, J.)
    v. United States, No. 11-1324 (D.C. Cir. July 10, 2013) (E.B. Br.).
    We reject Bahlul’s contention that the Government abandoned its
    forfeiture argument by conceding in its supplemental brief to the
    panel after Hamdan II that Bahlul’s convictions should be vacated.
    That brief was directed to a panel of this Court, which was bound
    by Hamdan II’s avoidance of the ex post facto issue. See Hamdan
    II, 696 F.3d at 1248 n.7. Only at the en banc stage was it possible
    for the Government to attack Hamdan II’s statutory construction
    and therefore put the Ex Post Facto Clause—and the applicable
    standard of review—back in play.
    14
    (quotation marks omitted); Breedlove, 204 F.3d at 270.
    Accordingly, we review his convictions for plain error.6
    6
    Three of our colleagues cite Rules 905 and 907 of the Rules
    of Military Commissions for the notion that Bahlul’s ex post facto
    argument is “not forfeitable.” Opinion of Judge Kavanaugh
    (Kavanaugh Op.) 31; accord Opinion of Judge Rogers (Rogers Op.)
    26–27; Opinion of Judge Brown (Brown Op.) 2. Bahlul’s briefs do
    not mention these rules or suggest this argument. Moreover, Rules
    905 and 907 both explicitly refer to waiver, see MANUAL FOR
    MILITARY COMMISSIONS, pt. II, at 83–84, 87 (2007), whereas we
    conclude instead that Bahlul forfeited his argument. “Although
    jurists often use the words interchangeably,” Kontrick v. Ryan, 
    540 U.S. 443
    , 458 n.13 (2004), waiver and forfeiture are not the same,
    see Olano, 
    507 U.S. at 733
    ; see also United States v. Weathers, 
    186 F.3d 948
    , 955 (D.C. Cir. 1999) (explaining difference while
    interpreting similar provision in Federal Rules of Criminal
    Procedure regarding waiver of pretrial motions). Nor is Bahlul’s ex
    post facto argument “jurisdictional.” See Rogers Op. 26; Brown
    Op. 2; Kavanaugh Op. 31. As discussed infra pp. 16–17, the 2006
    MCA explicitly confers jurisdiction on military commissions to try
    the charged offenses.        The question whether that Act is
    unconstitutional does not involve “ ‘the courts’ statutory or
    constitutional power to adjudicate the case.’ ” United States v.
    Cotton, 
    535 U.S. 625
    , 630 (2002) (quoting Steel Co. v. Citizens for
    a Better Env’t, 
    523 U.S. 83
    , 89 (1998)); United States v. Williams,
    
    341 U.S. 58
    , 66 (1951) (“Even the unconstitutionality of the statute
    under which the proceeding is brought does not oust a court of
    jurisdiction.”); Lamar v. United States, 
    240 U.S. 60
    , 65 (1916)
    (“The objection that the indictment does not charge a crime against
    the United States goes only to the merits of the case.”); see also
    United States v. Delgado-Garcia, 
    374 F.3d 1337
    , 1342–43 (D.C.
    Cir. 2004) (explaining limits of so-called “Blackledge/Menna”
    exception relied on by Bahlul). Nor are we persuaded that Bahlul’s
    ex post facto argument is non-forfeitable because it amounts to an
    argument that the indictment fails to “allege an offense.” Rogers
    Op. 27; Kavanaugh Op. 32. Failure to state an offense is simply
    another way of saying there is a defect in the indictment—as
    15
    Two of our colleagues contend that, by applying only
    plain-error review, we have provided insufficient clarity in
    this case. They argue that the Executive Branch’s need for
    guidance in this area warrants de novo review. Brown Op. 1,
    24; Kavanaugh Op. 34. But the Government itself has asked
    that we apply plain-error review. E.B. Br. of the United
    States 63. Indeed, at oral argument, it insisted that we do so,
    notwithstanding the potential lack of “clarity” that such
    review might entail. Oral Arg. Tr. 45.
    III. Statutory Analysis
    As noted, Hamdan II held that the 2006 MCA “does not
    authorize retroactive prosecution for conduct committed
    before enactment of that Act unless the conduct was already
    prohibited under existing U.S. law as a war crime triable by
    military commission.” 696 F.3d at 1248. Because we
    conclude, for the reasons that follow, that the 2006 MCA is
    unambiguous in its intent to authorize retroactive prosecution
    for the crimes enumerated in the statute—regardless of their
    pre-existing law-of-war status—we now overrule Hamdan
    II’s statutory holding. See United States v. Burwell, 
    690 F.3d 500
    , 504 (D.C. Cir. 2012) (en banc); Critical Mass Energy
    Project v. NRC, 
    975 F.2d 871
    , 876 (D.C. Cir. 1992) (en banc);
    evidenced by Rule 907’s cross-reference to Rule 307(c), which sets
    forth the criteria for charges and specifications. See MANUAL FOR
    MILITARY COMMISSIONS, pt. II, at 15–16; see also Delgado-
    Garcia, 
    374 F.3d at
    1341–42 (“[T]he question of an indictment’s
    failure to state an offense is an issue that goes to the merits of a
    case . . . .”). As Cotton makes clear, such a claim can be forfeited.
    
    535 U.S. at
    630–31.
    16
    Save Our Cumberland Mountains, Inc. v. Hodel, 
    857 F.2d 1516
    , 1524 (D.C. Cir. 1988) (en banc).7
    A. The 2006 MCA is Unambiguous
    The 2006 MCA confers jurisdiction on military
    commissions to try “any offense made punishable by this
    chapter or the law of war when committed by an alien
    unlawful enemy combatant before, on, or after September 11,
    2001.” 10 U.S.C. § 948d(a) (2006) (emphases added).
    “Any,” in this context, means “all.” See OXFORD ENGLISH
    DICTIONARY 539 (2d ed. 1989) (“indifference as to the
    particular one or ones that may be selected”); see also Dep’t
    of Housing & Urban Dev. v. Rucker, 
    535 U.S. 125
    , 131
    (2002); United States v. Gonzales, 
    520 U.S. 1
    , 5 (1997). The
    “offense[s] made punishable by this chapter” include the
    charges of which Bahlul was convicted: conspiracy to commit
    war crimes, providing material support for terrorism and
    solicitation of others to commit war crimes. 10 U.S.C.
    §§ 950u, 950v(b)(25), 950v(b)(28) (2006). There could
    hardly be a clearer statement of the Congress’s intent to
    confer jurisdiction on military commissions to try the
    enumerated crimes regardless whether they occurred “before,
    on, or after September 11, 2001.” And the provisions of the
    statute enumerating the crimes triable thereunder expressly
    “do not preclude trial for crimes that occurred before the date
    of the enactment of this chapter.” 10 U.S.C. § 950p(b)
    (2006). For good reason: If it were otherwise, section 948d’s
    conferral of jurisdiction to prosecute the enumerated crimes
    occurring on or before September 11, 2001 would be
    7
    Although perhaps uncommon, overruling our precedent on
    plain-error review is within the authority of the en banc court. See,
    e.g., United States v. Padilla, 
    415 F.3d 211
    , 217–18 (1st Cir. 2005)
    (en banc) (recognizing power of en banc court to overrule circuit
    precedent under plain-error review but declining to do so).
    17
    inoperative. See Corley v. United States, 
    556 U.S. 303
    , 314
    (2009) (“A statute should be construed so that effect is given
    to all its provisions, so that no part will be inoperative or
    superfluous, void or insignificant.” (quotation marks, brackets
    and ellipsis omitted)). Although we presume that statutes
    apply only prospectively “absent clear congressional intent”
    to the contrary, that presumption is overcome by the clear
    language of the 2006 MCA. Landgraf v. USI Film Prods.,
    
    511 U.S. 244
    , 280 (1994); see also Johnson v. United States,
    
    529 U.S. 694
    , 701 (2000) (clear statement of intent overcomes
    presumption against retroactivity); Martin v. Hadix, 
    527 U.S. 343
    , 353–54 (1999) (“ ‘unambiguous directive’ or ‘express
    command’ ” overcomes presumption against retroactivity);
    Reynolds v. M’Arthur, 27 U.S. (2 Pet.) 417, 434 (1829)
    (Marshall, C.J.) (“[L]aws by which human action is to be
    regulated . . . are never to be construed retrospectively unless
    the language of the act shall render such construction
    indispensable.”).
    Review of the inter-branch dialogue which brought about
    the 2006 MCA confirms the Congress’s intent to apply all of
    the statute’s enumerated crimes retroactively.            See
    Boumediene v. Bush, 
    553 U.S. 723
    , 738 (2008)
    (“acknowledg[ing] . . . the litigation history that prompted
    Congress to enact the MCA”). In Hamdan v. Rumsfeld, 
    548 U.S. 557
     (2006), the Supreme Court considered the
    President’s order that a military commission try Hamdan, a
    Guantanamo detainee, for one of the very crimes of which
    Bahlul was convicted: conspiracy to commit war crimes.
    Hamdan challenged the President’s authority to convene the
    military commission by petitioning for habeas corpus relief
    and the Supreme Court’s resulting decision initiated two
    games of interpretive ping-pong between the judiciary and the
    legislature. One involves the issue presented here: whether
    conspiracy is triable by a law-of-war military commission. In
    18
    Hamdan, four justices concluded that it was not triable under
    the extant statute (section 821) and three concluded that it
    was. Compare Hamdan, 
    548 U.S. at
    603–13 (plurality
    opinion of Stevens, J.), with 
    id.
     at 697–704 (Thomas, J.,
    dissenting). Four justices also “specifically invited Congress
    to clarify the scope of the President’s statutory authority to
    use military commissions to try unlawful alien enemy
    combatants for war crimes.” Hamdan II, 696 F.3d at 1243;
    see Hamdan, 
    548 U.S. at 636
     (Breyer, J., concurring)
    (“Nothing prevents the President from returning to Congress
    to seek the authority he believes necessary.”); 
    id. at 637
    (Kennedy, J., concurring) (“If Congress, after due
    consideration, deems it appropriate to change the controlling
    statutes, in conformance with the Constitution and other laws,
    it has the power and prerogative to do so.”).
    The Congress answered the Court’s invitation with the
    2006 MCA, which provides the President the very power he
    sought to exercise in Hamdan—the power to try the 9/11
    perpetrators for conspiracy—by including conspiracy as an
    offense triable by military commission, 10 U.S.C.
    § 950v(b)(28) (2006), and by conferring jurisdiction on
    military commissions to try alien unlawful enemy combatants
    for conspiracy based on conduct that occurred “before, on, or
    after September 11, 2001,” id. § 948d(a). We must heed this
    inter-branch dialogue, as Boumediene instructs. 
    553 U.S. at 738
    .
    If this sounds familiar, it does so because it mirrors a
    second game of interpretive ping-pong begun in Hamdan.
    There, the Court also addressed the Government’s contention
    that section 1005(e)(1) of the Detainee Treatment Act of 2005
    (DTA), Pub. L. 109-148, 
    119 Stat. 2739
    , 2741–42—enacted
    after the Court’s grant of certiorari in Hamdan—ousted it of
    jurisdiction to entertain Hamdan’s habeas petition. Hamdan,
    19
    
    548 U.S. at 572
    . After a lengthy statutory analysis, the Court
    construed the DTA to apply only to petitions filed after the
    DTA’s enactment and, because Hamdan’s petition was filed
    before, the statute did not apply. 
    Id.
     at 576–84. In construing
    the DTA as it did, the Court avoided addressing “grave
    questions about Congress’ authority to impinge upon this
    Court’s appellate jurisdiction, particularly in habeas cases”
    and whether the Congress had unconstitutionally suspended
    the writ of habeas corpus. 
    Id. at 575
    . Although the Court
    relied on “[o]rdinary principles of statutory construction” to
    reach its result, 
    id.,
     its practical message to the Congress was
    clear: Stripping the courts of jurisdiction over detainees’
    pending habeas petitions must be done unambiguously. Three
    justices dissented, arguing that the DTA was already
    unambiguous in its intent to repeal the Court’s jurisdiction.
    
    Id.
     at 656–69 (Scalia, J., dissenting).
    The Congress returned serve in the 2006 MCA. Section
    7(b) clarified that the bar to habeas jurisdiction applied to “all
    cases, without exception, pending on or after the date” of the
    statute’s enactment. 2006 MCA, § 7(b), 120 Stat. at 2636.
    Two years later, a detainee whose habeas petition was
    pending at the time of the 2006 MCA’s enactment argued that
    the statute did not apply to his case because section 7(b) was
    not a “sufficiently clear statement of congressional intent to
    strip the federal courts of jurisdiction in pending cases.”
    Boumediene, 
    553 U.S. at 737
    . This time, the Court rejected
    the argument. It explained:
    If the Court invokes a clear statement rule to advise
    that certain statutory interpretations are favored in
    order to avoid constitutional difficulties, Congress
    can make an informed legislative choice either to
    amend the statute or to retain its existing text. If
    Congress amends, its intent must be respected even if
    20
    a difficult constitutional question is presented. The
    usual presumption is that Members of Congress, in
    accord with their oath of office, considered the
    constitutional issue and determined the amended
    statute to be a lawful one; and the Judiciary, in light
    of that determination, proceeds to its own
    independent judgment on the constitutional question
    when required to do so in a proper case.
    If this ongoing dialogue between and among the
    branches of Government is to be respected, we
    cannot ignore that the MCA was a direct response to
    Hamdan’s holding that the DTA’s jurisdiction-
    stripping provision had no application to pending
    cases.
    
    Id. at 738
     (emphases added). Having avoided the Suspension
    Clause issue in Hamdan by virtue of its construction of the
    statute and having been answered by the Congress’s
    reenactment of its retroactive intent, the Court had no choice
    but to resolve the difficult constitutional question presented
    (whether the MCA violated the Suspension Clause).
    The same thing happened here. In enacting the military
    commission provisions of the 2006 MCA, the Congress
    plainly intended to give the President the power which
    Hamdan held it had not previously supplied—just as the 2006
    MCA clarified that in fact the Congress did intend section
    7(b)’s ouster of habeas jurisdiction to apply to pending cases.
    The legislative history confirms this view. See Boumediene,
    
    553 U.S. at 739
     (“The Court of Appeals was correct to take
    note of the legislative history when construing the statute . . .
    .”). Supporters and opponents of the legislation alike agreed
    that the 2006 MCA’s purpose was to authorize the trial by
    21
    military commission of the 9/11 conspirators.8 And because
    the 9/11 conspiracy took place long before 2006, the statute
    could accomplish its explicit purpose only if it applied to pre-
    enactment conduct. As the Court itself made clear, “we
    cannot ignore that the [2006] MCA was a direct response to
    Hamdan’s holding.” Boumediene, 
    553 U.S. at 739
    .
    Reading the MCA in this context and given the
    unequivocal nature of its jurisdictional grant, we conclude the
    8
    The legislative history is overwhelmingly in favor of
    retroactive application of the MCA’s provisions as a response to
    Hamdan. See, e.g., 152 CONG. REC. H7533 (daily ed. Sept. 27,
    2006) (statement of Rep. Hunter) (“I can’t think of a better way to
    honor the fifth anniversary of September 11 than by establishing a
    system to prosecute the terrorists who on that day murdered
    thousands of innocent civilians . . . .”); 
    id.
     (“Without [the 2006
    MCA], the United States has no effective means to try and punish
    the perpetrators of September 11, the attack on the USS Cole and
    the embassy bombings.”); 
    id.
     at H7536 (statement of Rep. Saxton)
    (“We have carefully narrowed and crafted the provisions of this bill
    to enable the United States to prosecute the perpetrators of the 1998
    bombings of the American embassies in Kenya and Tanzania, the
    2000 attack on the USS Cole, and other crimes that have been
    committed.”); 
    id.
     (“Importantly, this bill allows, as all Americans
    believe it should, the criminal prosecutions of those who
    purposefully and materially supported [the 9/11 conspiracy].”); 
    id.
    at H7545 (statement of Rep. Sensenbrenner) (“[The 2006 MCA] is
    about prosecuting the most dangerous terrorists America has ever
    confronted . . . like Khalid Sheik Mohammed, the mastermind of
    the 9/11 attacks, or Ahbd al-Nashiri, who planned the attack on the
    USS Cole.”); 
    id.
     at H7552 (statement of Rep. Boehner); 
    id.
     at
    S10243 (statement of Sen. Frist) (“Until Congress passes [the 2006
    MCA], terrorists such as Khalid Shaikh Mohammed cannot be tried
    for war crimes . . . .”); cf. 
    id.
     at H7536 (statement of Rep. Skelton)
    (opposing 2006 MCA because it “creates” “ex post facto laws”).
    22
    2006 MCA unambiguously authorizes Bahlul’s prosecution
    for the charged offenses based on pre-2006 conduct.
    B. The Avoidance Canon is Inapplicable
    Hamdan II’s contrary conclusion turned on the following
    provision of the 2006 MCA:
    (a) PURPOSE.—The provisions of this subchapter
    codify offenses that have traditionally been triable by
    military commissions. This chapter does not
    establish new crimes that did not exist before its
    enactment, but rather codifies those crimes for trial
    by military commission.
    (b) EFFECT.—Because the provisions of this
    subchapter (including provisions that incorporate
    definitions in other provisions of law) are declarative
    of existing law, they do not preclude trial for crimes
    that occurred before the date of the enactment of this
    chapter.
    10 U.S.C. § 950p (2006). In Hamdan II, the Court read this
    provision to reflect the Congress’s “belie[f] that the Act
    codified no new crimes and thus posed no ex post facto
    problem.” 696 F.3d at 1247. Because the Congress was
    wrong in its textually stated premise—i.e., the Act did codify
    new war crimes—the Court found “at least something of an
    ambiguity” in the statute. Id. at 1248. It then turned to the
    avoidance canon to resolve the ambiguity, concluding that the
    Congress intended to authorize retroactive prosecution only if
    “the conduct was already prohibited under existing U.S. law
    as a war crime triable by military commission.” Id.
    23
    The “avoidance canon” reflects a fundamental principle
    of judicial restraint. See Ashwander v. TVA, 
    297 U.S. 288
    ,
    341–48 (1936) (Brandeis, J., concurring). But “[t]he canon of
    constitutional avoidance comes into play only when, after the
    application of ordinary textual analysis, the statute is found to
    be susceptible of more than one construction; and the canon
    functions as a means of choosing between them.” Clark v.
    Martinez, 
    543 U.S. 371
    , 385 (2005) (emphasis in original);
    see also Milavetz, Gallop & Milavetz, P.A. v. United States,
    
    559 U.S. 229
    , 239 (2010). If, after applying ordinary
    principles of textual analysis, the statute is not genuinely open
    to two constructions, the “canon of constitutional avoidance
    does not apply.” Gonzales v. Carhart, 
    550 U.S. 124
    , 154
    (2007). Because the 2006 MCA unqualifiedly confers
    jurisdiction on military commissions to try “any offense made
    punishable by this chapter or the law of war when committed
    by an alien unlawful enemy combatant before, on, or after
    September 11, 2001,” 10 U.S.C. § 948d(a) (2006) (emphases
    added), it is not “fairly possible” to read the statute to apply
    only prospectively. United States v. Jin Fuey Moy, 
    241 U.S. 394
    , 401 (1916) (Holmes, J.).
    Hamdan II perceived a “tight causal link between (i)
    Congress’s belief that the statute codified only crimes under
    pre-existing law and (ii) Congress’s statement that the new
    statute could therefore apply to conduct before enactment.”
    696 F.3d at 1247–48. We think that link plainly affirms the
    Congress’s intent to apply the statute retroactively. “The
    Congress is a coequal branch of government whose Members
    take the same oath we do to uphold the Constitution of the
    United States.” Rostker v. Goldberg, 
    453 U.S. 57
    , 64 (1981).
    We assume that, in meeting that oath, it “legislates in the light
    of constitutional limitations.” Rust v. Sullivan, 
    500 U.S. 173
    ,
    191 (1991); see also Edward J. DeBartolo Corp. v. Fla. Gulf
    Coast Bldg. & Constr. Trades Council, 
    485 U.S. 568
    , 575
    24
    (1988); FTC v. Am. Tobacco Co., 
    264 U.S. 298
    , 305–06
    (1924); United States v. Harris, 
    106 U.S. 629
    , 635 (1883);
    Joint Anti-Fascist Refugee Comm. v. McGrath, 
    341 U.S. 123
    ,
    164 (1951) (Frankfurter, J., concurring). As section 950p
    makes abundantly clear, the Congress made precisely that
    assessment and, whether right or wrong, concluded that the
    statute fell within the constitutional limits of its legislative
    authority. See City of Boerne v. Flores, 
    521 U.S. 507
    , 535
    (1997) (“When Congress acts within its sphere of power and
    responsibilities, it has not just the right but the duty to make
    its own informed judgment on the meaning and force of the
    Constitution.”); United States v. Nixon, 
    418 U.S. 683
    , 703
    (1974) (“In the performance of assigned constitutional duties
    each branch of the Government must initially interpret the
    Constitution, and the interpretation of its powers by any
    branch is due great respect from the others.”). Indeed, the
    legislative history reveals the breadth of the Congress’s
    debate on the statute’s constitutionality. See, e.g., H.R. Rep.
    No. 109-664, at 25 (“For the reasons stated in Justice
    Thomas’s opinion [in Hamdan], the Committee [on Armed
    Services] views conspiracy as a separate offense punishable
    by military commissions.”).
    The “ambiguity” Hamdan II identified was the
    Congress’s failure to address what it “would . . . have wanted”
    if it “had known that the Act was codifying some new
    crimes.” 696 F.3d at 1247. In other words, Hamdan II found
    the statute ambiguous because the Congress did not include in
    the text of the statute alternative language in case it was
    wrong in its reading of the law on which it premised its
    legislation. But the Congress always legislates on the basis of
    some set of facts or premises it believes to be true. It holds
    hearings and investigates precisely for the purpose of
    acquiring facts and then legislates on the basis of those facts.
    Because it believes to be true the facts on which it bases its
    25
    legislation, the Congress seldom (if ever) includes instructions
    on what to do if those facts are proven incorrect. Here, the
    Congress authorized prosecution for “any offense made
    punishable by” the 2006 MCA, including offenses based on
    pre-enactment conduct, precisely because it believed that all
    of the offenses were already triable by military commission.
    The Congress’s plainly expressed belief about pre-enactment
    law should govern our understanding of the Congress’s intent
    expressed in the text of the statute. If judicial inquiry reveals
    that the Congress was mistaken, it is not our task to rewrite
    the statute to conform with the actual state of the law but
    rather to strike it down insofar as the Congress’s mistake
    renders the statute unconstitutional. See Ass’n of Am.
    Railroads v. U.S. Dep’t of Transp., 
    721 F.3d 666
    , 673 n.7
    (D.C. Cir. 2013) (“The constitutional avoidance canon is an
    interpretive aid, not an invitation to rewrite statutes to satisfy
    constitutional strictures.”), cert. granted (June 23, 2014).
    Moreover, the avoidance canon ordinarily requires no
    speculation into the Congress’s hypothetical intent: If the
    statute’s text is ambiguous, we choose a constitutional
    construction over an unconstitutional one. Here, however, the
    “ambiguity” lies not in the text itself but in the text when read
    in light of Hamdan II’s subsequent finding that the premise on
    which the text is based is wrong. That is, the “ambiguity” lies
    in the existence of matters unknown to the Congress. But
    “[w]e cannot replace the actual text with speculation as to
    Congress’ intent,” Magwood v. Patterson, 
    130 S. Ct. 2788
    ,
    2798 (2010), nor can we “divin[e] what Congress would have
    wanted if it had thought of the situation before the court,”
    Morrison v. Nat’l Australia Bank Ltd., 
    130 S. Ct. 2869
    , 2881
    (2010); see also United States v. Public Utilities Comm’n of
    Cal., 
    345 U.S. 295
    , 319 (1953) (Jackson, J., concurring)
    (“Never having been a Congressman, I am handicapped in
    that weird endeavor. That process seems to me not
    26
    interpretation of a statute but creation of a statute.”). For that
    reason, “our inquiry focuses on an analysis of the textual
    product of Congress’ efforts, not on speculation as to the
    internal thought processes of its Members.” Carter v. United
    States, 
    530 U.S. 255
    , 272 (2000); see also Gardner v. Collins,
    27 U.S. (2 Pet.) 58, 93 (1829) (“What the legislative intention
    was, can be derived only from the words they have used; and
    we cannot speculate beyond the reasonable import of these
    words.”).
    Even if it may raise difficult constitutional questions, the
    statutory text remains the gravamen of our interpretive
    inquiry. See United States v. Raynor, 
    302 U.S. 540
    , 552
    (1938). “Although [we] will often strain to construe
    legislation so as to save it against constitutional attack,”
    Aptheker v. Sec’y of State, 
    378 U.S. 500
    , 515 (1964)
    (quotation marks omitted), a court cannot “rewrite a law to
    conform it to constitutional requirements, for doing so would
    constitute a serious invasion of the legislative domain,”
    United States v. Stevens, 
    559 U.S. 460
    , 481 (2010) (quotation
    marks, ellipsis and citations omitted). “Here the intention of
    the Congress is revealed too distinctly to permit us to ignore it
    because of mere misgivings as to power. The problem must
    be faced and answered.” George Moore Ice Cream Co. v.
    Rose, 
    289 U.S. 373
    , 379 (1933) (Cardozo, J.).
    IV. Bahlul’s Ex Post Facto Challenge
    Because the Congress’s intent to authorize retroactive
    prosecution of the charged offenses is clear, we must address
    Bahlul’s ex post facto argument. See Cohens v. Virginia, 19
    U.S. (6 Wheat.) 264, 404 (1821) (Marshall, C.J.) (“Questions
    may occur which we would gladly avoid; but we cannot avoid
    them. All we can do is, to exercise our best judgment, and
    conscientiously to perform our duty.”). As noted, we may
    27
    overturn Bahlul’s convictions only if they constitute plain
    constitutional error.
    The Constitution prohibits the Congress from enacting
    any “ex post facto Law.” U.S. CONST. art. I, § 9, cl. 3. “The
    phrase ex post facto law was a term of art with an established
    meaning at the time of the framing.” Peugh v. United States,
    
    133 S. Ct. 2072
    , 2081 (2013) (quoting Collins v. Youngblood,
    
    497 U.S. 37
    , 41 (1990)) (quotation marks omitted). In Calder
    v. Bull, Justice Chase set forth his understanding of that
    meaning:
    1st. Every law that makes an action, done before the
    passing of the law, and which was innocent when
    done, criminal; and punishes such action. 2nd. Every
    law that aggravates a crime, or makes it greater than
    it was, when committed. 3rd. Every law that changes
    the punishment, and inflicts a greater punishment,
    than the law annexed to the crime, when committed.
    4th. Every law that alters the legal rules of evidence,
    and receives less, or different, testimony, than the
    law required at the time of the commission of the
    offence, in order to convict the offender.
    3 U.S. (3 Dall.) 386, 390 (1798) (opinion of Chase, J.); see
    Peugh, 
    133 S. Ct. at 2081
     (reciting Justice Chase’s
    formulation); Carmell v. Texas, 
    529 U.S. 513
    , 525 (2000)
    (Supreme Court has “repeatedly endorsed” Justice Chase’s
    formulation); see also 
    id.
     at 537–39 (noting that Collins did
    not eliminate Justice Chase’s fourth category).
    In our order granting en banc review, we asked the
    parties to brief whether the Ex Post Facto Clause applies in
    cases involving aliens detained at Guantanamo.          The
    Government has taken the position that it does. Although we
    28
    are not obligated to accept the Government’s concession, see
    Young v. United States, 
    315 U.S. 257
    , 258–59 (1942); United
    States v. Baldwin, 
    563 F.3d 490
    , 491 (D.C. Cir. 2009), we
    will assume without deciding that the Ex Post Facto Clause
    applies at Guantanamo. In so doing, we are “not to be
    understood as remotely intimating in any degree an opinion
    on the question.” Petite v. United States, 
    361 U.S. 529
    , 531
    (1960) (per curiam); see also Casey v. United States, 
    343 U.S. 808
    , 808 (1952) (per curiam) (“To accept in this case [the
    Solicitor General’s] confession of error would not involve the
    establishment of any precedent.”); United States v. Bell, 
    991 F.2d 1445
    , 1447–48 (8th Cir. 1993).9
    A. Conspiracy
    We reject Bahlul’s ex post facto challenge to his
    conspiracy conviction for two independent and alternative
    reasons. First, the conduct for which he was convicted was
    already criminalized under 
    18 U.S.C. § 2332
    (b) (section
    2332(b)) when Bahlul engaged in it. It is not “plain” that it
    violates the Ex Post Facto Clause to try a pre-existing federal
    criminal offense in a military commission and any difference
    between the elements of that offense and the conspiracy
    charge in the 2006 MCA does not seriously affect the
    fairness, integrity or public reputation of judicial proceedings.
    Second, it is not “plain” that conspiracy was not already
    9
    Were we to decide this issue de novo, Judge Henderson
    would conclude that the Ex Post Facto Clause does not apply in
    cases involving aliens detained at Guantanamo, for the reasons
    stated in her separate concurring opinion. Chief Judge Garland and
    Judges Tatel and Griffith would conclude that the Clause does
    apply in such cases, for the reasons stated in the first two
    paragraphs of Part II.B of Judge Rogers’s opinion and in Note 3 of
    Judge Kavanaugh’s opinion.
    29
    triable by law-of-war military commission under 
    10 U.S.C. § 821
     when Bahlul’s conduct occurred.
    1. Section 2332(b)
    Bahlul was convicted of conspiracy to commit seven war
    crimes enumerated in the 2006 MCA, including the murder of
    protected persons.10 Although the 2006 MCA post-dates
    Bahlul’s conduct, section 2332(b) has long been on the books,
    making it a crime to, “outside the United States,” “engage[] in
    a conspiracy to kill[] a national of the United States.” 
    18 U.S.C. § 2332
    (b); see Omnibus Diplomatic Security and
    Antiterrorism Act of 1986, Pub. L. No. 99-399, § 1202(a),
    
    100 Stat. 853
    , 896. Section 2332(b) is not an offense triable
    by military commission but, the Government argues, “[t]he
    fact that the MCA provides a different forum for adjudicating
    such conduct does not implicate ex post facto concerns.” E.B.
    Br. of United States 67. We agree. See infra p. 53
    (remanding to panel to determine Bahlul’s other constitutional
    challenges).
    The right to be tried in a particular forum is not the sort
    of right the Ex Post Facto Clause protects. See Collins, 
    497 U.S. at 51
    . In Collins, the Supreme Court sifted through its
    Ex Post Facto Clause precedent, noting that some cases had
    10
    Specifically, the 2006 MCA provides: “Any person subject
    to this chapter who conspires to commit one or more substantive
    offenses triable by military commission under this chapter, and who
    knowingly does any overt act to effect the object of the conspiracy,
    shall be punished . . . .” 10 U.S.C. § 950v(b)(28). The murder of
    protected persons is the “intentional[]” killing of one or more
    “protected persons.” Id. § 950v(b)(1). A protected person is “any
    person entitled to protection under one or more of the Geneva
    Conventions, including . . . civilians not taking an active part in
    hostilities.” Id. § 950v(a)(2)(A).
    30
    said that a “procedural” change—i.e., a “change[] in the
    procedures by which a criminal case is adjudicated”—may
    violate the Ex Post Facto Clause if the change “affects
    matters of substance” by “depriving a defendant of substantial
    protections with which the existing law surrounds the person
    accused of crime or arbitrarily infringing upon substantial
    personal rights.” Id. at 45 (citations, brackets and quotation
    marks omitted). The Court observed that such language had
    “imported confusion” into its doctrine and it attempted to
    reconcile that language so as to not enlarge the Ex Post Facto
    Clause’s application beyond laws that “make innocent acts
    criminal, alter the nature of the offense, or increase the
    punishment.” Id. at 46. One case that could not be reconciled
    was Thompson v. Utah, in which the Court had found that a
    change in Utah law reducing the size of criminal juries from
    12 to 8 persons violated the Ex Post Facto Clause by
    depriving the defendant of “a substantial right involved in his
    liberty.” 
    170 U.S. 343
    , 352–53 (1898). The Court overruled
    Thompson in Collins, explaining that the reduced size of the
    jury was not in fact an ex post facto violation because “[t]he
    right to jury trial provided by the Sixth Amendment is
    obviously a ‘substantial’ one, but it is not a right that has
    anything to do with the definition of crimes, defenses, or
    punishments, which is the concern of the Ex Post Facto
    Clause.” Collins, 
    497 U.S. at 51
    .
    Similarly, in Cook v. United States, the Court held that an
    act vesting jurisdiction over a crime in a newly formed
    judicial district does not violate the Ex Post Facto Clause
    because “[i]t only . . . subjects the accused to trial in th[e new]
    district rather than in the court of some other judicial district
    established by the government against whose laws the offense
    was committed. This does not alter the situation of the
    defendants in respect to their offense or its consequences.”
    
    138 U.S. 157
    , 183 (1891); accord Gut v. Minnesota, 
    76 U.S. 31
    35, 38 (1869) (“An ex post facto law does not involve, in any
    of its definitions, a change of the place of trial of an alleged
    offence after its commission.”); see also Duncan v. Missouri,
    
    152 U.S. 377
    , 382–83 (1894) (suggesting no ex post facto
    violation where defendant’s appeal was heard by smaller
    appellate panel than provided for at time of his offense).
    It is therefore not a plain ex post facto violation to
    transfer jurisdiction over a crime from an Article III court to a
    military commission because such a transfer does not have
    anything to do with the definition of the crime, the defenses or
    the punishment. That is so regardless of the different
    evidentiary rules that apply under the 2006 MCA. See
    Carmell, 
    529 U.S. at
    533 n.23 (change in “[o]rdinary rules of
    evidence . . . do[es] not violate the [Ex Post Facto] Clause”);
    
    id.
     at 542–47; Collins, 
    497 U.S. at
    43 n.3; Beazell v. Ohio,
    
    269 U.S. 167
    , 171 (1925); Thompson v. Missouri, 
    171 U.S. 380
    , 386–88 (1898); Hopt v. Utah, 
    110 U.S. 574
    , 589–90
    (1884). Nor is this a case like Carmell, where a law
    retroactively reduced the “quantum of evidence necessary to
    sustain a conviction,” 529 U.S. at 530; the 2006 MCA
    requires the Government to prove guilt beyond a reasonable
    doubt, see 10 U.S.C. § 949l(c); see also Trial Tr. 233, 878
    (military judge’s instructions to commission).11
    11
    Likewise, the greater maximum sentence provided in the
    2006 MCA—the death penalty, as opposed to a maximum of life
    imprisonment under section 2332(b)—does not present an ex post
    facto problem. The Government did not seek the death penalty, see
    Trial Tr. 958, and the military judge’s instructions to the
    commission before sentencing specifically declared that “[t]he
    maximum punishment that may be adjudged in this case is
    confinement for life,” id. at 949. Further, the 2006 MCA requires a
    12-member military commission if the death penalty is sought, see
    10 U.S.C. § 949m(c), and Bahlul’s commission had only nine
    members, see Trial Tr. 285. There was therefore no risk that the
    32
    Our inquiry is not ended, however, because the 2006
    MCA conspiracy-to-murder-protected-persons charge and
    section 2332(b) do not have identical elements.           The
    difference is a potential problem because the Ex Post Facto
    Clause prohibits “retrospectively eliminating an element of
    the offense” and thus “subvert[ing] the presumption of
    innocence by reducing the number of elements [the
    government] must prove to overcome that presumption.”
    Carmell, 529 U.S. at 532. Both statutes require the existence
    of a conspiracy and an overt act in furtherance thereof. See
    
    18 U.S.C. § 2332
    (b)(2); 10 U.S.C. § 950v(b)(28) (2006); see
    also Trial Tr. 846, 849–50 (military judge’s instructions to
    commission). The 2006 MCA conspiracy charge is in one
    sense more difficult to prove than section 2332(b) because it
    applies only to alien unlawful enemy combatants engaged in
    hostilities against the United States.       See 10 U.S.C.
    §§ 948b(a), 948c, 948d; see also Trial Tr. 843–45
    (instructions). But the 2006 MCA charge is in two ways
    easier to prove than a section 2332(b) charge. It does not
    require that the conspiracy occur “outside the United States”
    or that the conspiracy be to kill a “national of the United
    States,” as section 2332(b) does. It simply requires a
    conspiracy to murder “one or more protected persons.” Trial
    Tr. 850–51 (instructions); see supra n.10 (providing MCA’s
    definition of “protected person”). Although the two statutes
    are quite similar, then, the 2006 MCA conspiracy charge
    greater sentence included in the 2006 MCA affected Bahlul’s
    sentence. See Peugh, 
    133 S. Ct. at 2082
     (“The touchstone of this
    Court’s inquiry is whether a given change in law presents a
    sufficient risk of increasing the measure of punishment attached to
    the covered crimes.” (quotation marks omitted)).
    33
    eliminates two elements required to convict a defendant under
    section 2332(b).12
    Nevertheless, Bahlul cannot bear his burden of
    establishing that the elimination of the two elements
    “seriously affect[ed] the fairness, integrity or public
    reputation of judicial proceedings.” Olano, 
    507 U.S. at 732
    (quotation marks omitted); see United States v. Vonn, 
    535 U.S. 55
    , 62–63 (2002) (defendant bears burden of proving
    Olano’s fourth prong); see also United States v. Johnson, 
    331 F.3d 962
    , 967 (D.C. Cir. 2003) (proceeding directly to fourth
    prong if it can resolve appeal). He cannot satisfy the fourth
    prong because the charges against him and the commission’s
    findings necessarily included those elements and the evidence
    supporting them was undisputed. To explain why requires
    that we first discuss the most on-point Supreme Court
    precedent.
    In Johnson v. United States, the Supreme Court reviewed
    a defendant’s conviction for perjury where the district court
    had decided the issue of materiality itself rather than submit
    that issue to the jury, as the Court’s precedent requires. 
    520 U.S. 461
    , 463 (1997). The defendant did not object, however,
    so the Court reviewed his conviction for plain error. Because
    the evidence of the missing materiality element was
    12
    To be clear, Bahlul was convicted of conspiracy as a stand-
    alone offense that does not depend upon the completion of an
    object offense. See Trial Tr. 848. He was not charged with
    conspiracy as a theory of liability for a completed crime. See Trial
    Tr. 109–12 (Government amended charge by striking allegation
    that Bahlul joined “an enterprise of persons who share the common
    criminal purpose that involved . . . the commission . . . of one or
    more substantive offenses”); see also United States v. Ali, 
    718 F.3d 929
    , 941 (D.C. Cir. 2013) (noting difference between conspiracy as
    stand-alone offense and conspiracy as theory of liability).
    34
    “overwhelming” and “essentially uncontroverted at trial,” the
    Court concluded that the error, although plain, did not
    seriously affect the fairness, integrity or public reputation of
    judicial proceedings. Id. at 470; cf. Neder v. United States,
    
    527 U.S. 1
    , 19 (1999) (failure to submit element to jury was
    harmless error “where [the] defendant did not, and apparently
    could not, bring forth facts contesting the omitted element”).
    Similarly, in United States v. Cotton, the indictment failed to
    charge the drug quantity involved in the offense, as the
    Court’s precedent requires for any fact that enhances the
    otherwise applicable statutory maximum sentence. 
    535 U.S. 625
    , 627–28 (2002). After the jury found the defendants
    guilty of a narcotics conspiracy, the district court made drug
    quantity findings that enhanced the defendants’ statutory
    maximums. 
    Id. at 628
    . This was “error” and it was “plain”
    but the Court nevertheless upheld the convictions under
    Olano’s fourth prong. Because the evidence of the requisite
    drug quantity was “overwhelming” and “essentially
    uncontroverted,” the Court concluded that “[t]he real threat
    . . . to the fairness, integrity, and public reputation of judicial
    proceedings would be if [the defendants] . . . were to receive a
    sentence prescribed for those committing less substantial drug
    offenses because of an error that was never objected to at
    trial.” 
    Id.
     at 633–34 (quotation marks omitted); accord
    Johnson, 
    331 F.3d at
    966–70; United States v. Webb, 
    255 F.3d 890
    , 899–902 (D.C. Cir. 2001).
    Here, the evidence of the two missing elements was not
    simply “overwhelming” and “essentially uncontroverted”—it
    was entirely uncontroverted. Bahlul was charged with
    committing numerous overt acts “in Afghanistan, Pakistan
    and elsewhere” that furthered the conspiracy’s unlawful
    objects; those objects included the murder of protected
    persons. App. 122–25. He did not dispute that his conduct
    occurred outside the United States nor did he dispute that the
    35
    purpose of the conspiracy was to murder United States
    nationals. See Trial Tr. 167 (Bahlul: “And what I did . . . is to
    kill Americans . . . .”); 
    id.
     at 511–12 (“[Bahlul] does not
    consider anybody protected person[s] or civilians. . . . [A]s
    long as you’re a[n] American, you are a target.”). Indeed,
    several witnesses testified that Bahlul considered all
    Americans to be targets. Id. at 503, 512, 596, 653. The
    commission was instructed on the overt acts allegedly
    undertaken by Bahlul in furtherance of the conspiracy, see id.
    at 846–47, and was instructed that one of the conspiracy’s
    object offenses was the murder of protected persons, id. at
    850.      The commission specifically found that Bahlul
    committed ten overt acts, all of which took place outside the
    United States and several of which directly relate to the 9/11
    attacks that killed thousands of United States nationals. App.
    132–33. And it found that all seven of the alleged object
    offenses, including murder of protected persons, were objects
    of the conspiracy. App. 131. There is no scenario in which
    the commission could have found that Bahlul committed these
    overt acts yet rationally found that the conspiracy did not take
    place outside the United States and did not have as an object
    the murder of United States nationals. Accord Webb, 
    255 F.3d at 901
    . Although the commission was not specifically
    instructed that it had to find these two elements, the overt acts
    it did find Bahlul had committed necessarily included the two
    elements and Bahlul did not, and does not, dispute either.
    Therefore, although the 2006 MCA conspiracy offense, as
    charged here, does “eliminat[e] an element of the offense,”
    Carmell, 529 U.S. at 532, the omission did not seriously
    affect the fairness, integrity, or public reputation of the
    proceedings.
    36
    2. Section 821
    When Bahlul committed the crimes of which he was
    convicted, section 821 granted—and still grants—military
    commissions jurisdiction “with respect to offenders or
    offenses that by statute or by the law of war may be tried by
    military commissions.” 
    10 U.S.C. § 821
    . Section 821 and its
    predecessor statute have been on the books for nearly a
    century. See Pub. L. No. 64-242, 
    39 Stat. 619
    , 653 (1916);
    Pub. L. No. 66-242, 
    41 Stat. 759
    , 790 (1920); Pub. L. No. 81-
    506, 
    64 Stat. 107
    , 115 (1950); Madsen v. Kinsella, 
    343 U.S. 341
    , 350–51 & n.17 (1952). We must therefore ascertain
    whether conspiracy to commit war crimes was a “law of war”
    offense triable by military commission under section 821
    when Bahlul’s conduct occurred because, if so, Bahlul’s ex
    post facto argument fails.
    In answering this question, we do not write on a clean
    slate. In Hamdan, seven justices of the Supreme Court
    debated the question at length. Four justices concluded that
    conspiracy is not triable by military commission under section
    821. 
    548 U.S. at
    603–13 (plurality opinion of Stevens, J.).
    Three justices opined that it is. 
    Id.
     at 697–704 (Thomas, J.,
    dissenting). Both opinions scoured relevant international and
    domestic authorities but neither position garnered a majority.
    The case was resolved on other grounds and the eighth vote—
    one justice was recused—left the conspiracy question for
    another day, noting that the Congress may “provide further
    guidance in this area.” See 
    id. at 655
     (Kennedy, J.,
    concurring). In light of the uncertainty left by the split, it was
    not “plain” error to try Bahlul for conspiracy by military
    commission pursuant to section 821. See United States v.
    Terrell, 
    696 F.3d 1257
    , 1260 (D.C. Cir. 2012) (plain error met
    only if “its erroneous character” is established by “a clear
    precedent in the Supreme Court or this circuit”).
    37
    The reason for the uncertainty is not only the divided
    result in Hamdan but also the High Court’s failure to clearly
    resolve a subsidiary question:        What body of law is
    encompassed by section 821’s reference to the “law of war”?
    That dispute takes center stage here. Bahlul contends that
    “law of war” means the international law of war, full stop.
    The Government contends that we must look not only to
    international precedent but also “the common law of war
    developed in U.S. military tribunals.” E.B. Br. of United
    States 28; see also Oral Arg. Tr. 15 (“[W]e believe the law of
    war is the international law of war as supplemented by the
    experience and practice of our wars and our wartime
    tribunals.”). The answer is critical because the Government
    asserts that conspiracy is not an international law-of-war
    offense. See E.B. Br. of United States 34; Oral Arg. Tr. 15.
    In Hamdan II, the Court said that “law of war” as used in
    section 821 is a term of art that refers to the international law
    of war. 696 F.3d at 1248; see also id. at 1252 (noting that
    “U.S. precedents may inform the content of international
    law”); cf. Kavanaugh Op. 11 n.5 (stating that Hamdan II’s
    interpretation of section 821 “was not necessary to the
    result”). Language in several Supreme Court opinions
    supports that proposition. See, e.g., Quirin, 
    317 U.S. at
    27–28
    (“[T]his Court has recognized and applied the law of war as
    including that part of the law of nations which prescribes, for
    the conduct of war, the status, rights and duties of enemy
    nations as well as of enemy individuals.”); 
    id. at 29
    (describing law of war as “branch of international law”); see
    also Hamdan, 
    548 U.S. at 603
     (plurality) (citing Quirin and
    describing offense alleged therein as being “recognized as an
    offense against the law of war” both “in this country and
    internationally”); 
    id.
     at 610–11 (analyzing international law
    sources); 
    id. at 641
     (Kennedy, J., concurring) (“[T]he law of
    38
    war . . . is the body of international law governing armed
    conflict.” (citing Quirin, 
    317 U.S. at 28
    )); Madsen, 
    343 U.S. at
    354–55 (“The ‘law of war’ . . . includes at least that part of
    the law of nations which defines the powers and duties of
    belligerent powers occupying enemy territory pending the
    establishment of civil government.”); Yamashita, 
    327 U.S. at
    12–16 (analyzing international precedent in determining
    whether offense was violation of law of war); Rogers Op. 6–7
    (concluding on de novo review that section 821 refers to
    international law of war).         Several Executive Branch
    interpretations and scholarly articles also support that reading.
    See Hamdan II, 696 F.3d at 1248–49 & n.9 (collecting
    citations).
    On the other hand, section 821 might not be so limited
    (as two of our colleagues would hold on de novo review). See
    Brown Op. 3; Kavanaugh Op. 7–11; see also Hamdan, 
    548 U.S. at 689
     (Thomas, J., dissenting) (“[W]hether an offense is
    a violation of the law of war cognizable before a military
    commission must be determined pursuant to the system of
    common law applied by military tribunals . . . [which] is
    derived from the experience of our wars and our wartime
    tribunals and the laws and usages of war as understood and
    practiced by the civilized nations of the world.” (citations and
    quotation marks omitted)). Significantly, both the Hamdan
    plurality and dissent relied primarily on domestic precedent to
    ascertain whether conspiracy could be tried under section 821.
    See Hamdan, 
    548 U.S. at
    603–09 (plurality); 
    id.
     at 689–704
    (Thomas, J., dissenting).13      There is also language in
    Yamashita and Quirin that domestic precedent is an important
    13
    The Hamdan plurality did not expressly decide whether
    section 821’s reference to the “law of war” is limited to the
    international law of war. See Hamdan, 
    548 U.S. at
    604–13
    (plurality).
    39
    part of our inquiry. See Yamashita, 
    327 U.S. at 8
     (“[The
    Congress] adopted the system of military common law
    applied by military tribunals so far as it should be recognized
    and deemed applicable by the courts, and as further defined
    and supplemented by the Hague Convention . . . .”); Quirin,
    
    317 U.S. at
    31–35, 42 n.14 (evaluating domestic precedent to
    determine whether offense charged was law-of-war offense);
    see also Madsen, 
    343 U.S. at
    347–48. Moreover, as the
    Supreme Court has explained, when the Congress enacted
    section 821 and its predecessors, it intended to preserve, not
    limit, the pre-existing jurisdiction of military commissions.
    See Madsen, 
    343 U.S. at
    352–53; Yamashita, 
    327 U.S. at
    19–
    20; see also Hamdan, 
    548 U.S. at 593
     (majority) (“[T]he
    Quirin Court recognized that Congress had simply preserved
    what power, under the Constitution and the common law of
    war, the President had had before 1916 to convene military
    commissions—with the express condition that the President
    and those under his command comply with the law of war.”).
    It is therefore arguable that the Congress also intended to
    incorporate military commission precedents predating section
    821’s enactment. See Sekhar v. United States, 
    133 S. Ct. 2720
    , 2724 (2013) (“[I]f a word is obviously transplanted
    from another legal source, whether the common law or other
    legislation, it brings the old soil with it.” (quoting Felix
    Frankfurter, Some Reflections on the Reading of Statutes, 47
    COLUM. L. REV. 527, 537 (1947))); Lorillard v. Pons, 
    434 U.S. 575
    , 581 (1978) (“[W]here, as here, Congress adopts a
    new law incorporating sections of a prior law, Congress
    normally can be presumed to have had knowledge of the
    interpretation given to the incorporated law, at least insofar as
    it affects the new statute.”).
    Ultimately, we need not resolve de novo whether section
    821 is limited to the international law of war. It is sufficient
    for our purpose to say that, at the time of this appeal, the
    40
    answer to that question is not “obvious.” Olano, 
    507 U.S. at 734
    ; see Henderson v. United States, 
    133 S. Ct. 1121
    , 1130–
    31 (2013) (plainness of error determined at time of appeal).
    As seven justices did in Hamdan, we look to domestic
    wartime precedent to determine whether conspiracy has been
    traditionally triable by military commission. That precedent
    provides sufficient historical pedigree to sustain Bahlul’s
    conviction on plain-error review.
    Most notably, the individuals responsible for the
    assassination of President Abraham Lincoln were charged
    with a single offense—“combining, confederating, and
    conspiring . . . to kill and murder . . . Abraham Lincoln”—and
    were convicted of that offense by military commission.
    General Court-Martial Order No. 356, War Dep’t (July 5,
    1865), reprinted in H.R. DOC. NO. 55-314, at 696 (1899).14
    The specification of the offense includes several paragraphs,
    each of which sets forth a separate overt act done “in further
    prosecution of the unlawful and traitorous conspiracy.” 
    Id.
     at
    697–98; see also THE ASSASSINATION OF PRESIDENT LINCOLN
    AND THE TRIAL OF THE CONSPIRATORS 18–21 (New York,
    Moore, Wilstach & Baldwin 1865). A federal district court
    later denied three of the conspirators’ habeas petitions raising
    jurisdictional objections to the commission. Ex Parte Mudd,
    
    17 F. Cas. 954
     (S.D. Fla. 1868).
    President Andrew Johnson personally approved the
    convictions. In doing so, he considered the jurisdictional
    limits of military commissions: He asked Attorney General
    James Speed whether the accused could be tried for
    14
    The Hamdan plurality interpreted this precedent as
    convicting the conspirators only of the completed offense of
    assassination, not inchoate conspiracy. Hamdan, 
    548 U.S. at
    604
    n.35 (plurality). But see 
    id.
     at 699 n.12 (Thomas, J., dissenting)
    (finding it clear that inchoate conspiracy was tried).
    41
    conspiracy in a military commission. In a lengthy opinion,
    Attorney General Speed said they could. See Military
    Commissions, 11 Op. Att’y Gen. 297 (1865). We think this
    highest-level Executive Branch deliberation is worthy of
    respect in construing the law of war. Cf. Sosa v. Alvarez-
    Machain, 
    542 U.S. 692
    , 733–34 (2004) (looking “albeit
    cautiously” to sources like “controlling executive . . . act[s]”
    to ascertain current state of international law (quoting The
    Paquete Habana, 
    175 U.S. 677
    , 700 (1900)); Tel-Oren v.
    Libyan Arab Republic, 
    726 F.2d 774
    , 780 n.6 (D.C. Cir. 1984)
    (Edwards, J., concurring) (Attorney General opinions not
    binding but “entitled to some deference, especially where
    judicial decisions construing a statute are lacking”). Granted,
    the Attorney General’s framing of the question presented—
    “whether the persons charged with the offence of having
    assassinated the President can be tried before a military
    tribunal”—casts some doubt on whether he was addressing
    inchoate conspiracy or the offense of assassination. 11 Op.
    Att’y Gen. at 297; see Hamdan, 
    548 U.S. at
    604 n.35
    (plurality). But the Attorney General’s opinion was written
    after the commission had been convened and the convictions
    had been approved; he would therefore have been aware that
    the sole offense alleged was conspiracy.15 On the other hand,
    15
    Some doubt about the precise nature of the charge also
    appears in the transcript of the conspirators’ trial. Thomas Ewing,
    counsel for several of the defendants, objected to the ambiguity of
    the charge, stating that “[t]here is but one charge, in form, against
    the accused; but, in fact, there seem to be four charges, each
    alleging the commission of a separate and distinct offense.” THE
    ASSASSINATION OF PRESIDENT LINCOLN AND THE TRIAL OF THE
    CONSPIRATORS, supra, at 244. He listed what he perceived to be
    the four offenses charged: conspiracy, traitorously murdering
    President Lincoln, traitorously assaulting with intent to kill
    Secretary of State William Seward and lying in wait with intent to
    traitorously murder then-Vice President Johnson. Id. at 244–45.
    42
    that the Attorney General’s opinion was written after the
    convictions were approved may undermine its persuasive
    value, as it could be viewed as a post hoc rationalization for a
    decision already made.
    Either way, the Lincoln conspirators’ trial was a matter of
    paramount national importance and attracted intense public
    scrutiny. Thus, when the Congress enacted section 821’s
    predecessor—and “preserved what power, under the
    Constitution and the common law of war, the President had
    had before 1916 to convene military commissions,” Hamdan,
    
    548 U.S. at 593
     (majority)—it was no doubt familiar with at
    least one high-profile example of a conspiracy charge tried by
    a military commission. Because of the national prominence
    of the case and the highest-level Executive Branch
    involvement, we view the Lincoln conspirators’ trial as a
    particularly significant precedent.16
    The Judge Advocate responded that “[t]he general allegation is a
    conspiracy” and that “[t]he pleadings proceed, after averring this
    conspiracy, . . . to set forth clearly and specifically the part which it
    is believed and alleged each one of them took in the execution of
    that conspiracy.” Id. at 245; see also id. at 246–47 (further
    discussion of the charge).
    16
    William Winthrop—the Blackstone of military law—also
    concluded that conspiracy is an offense that is “both a crime against
    society and a violation of the laws of war.” WINTHROP, MILITARY
    LAW AND PRECEDENTS, supra, at 842; accord WILLIAM
    WINTHROP, A DIGEST OF OPINIONS OF THE JUDGE ADVOCATE
    GENERAL OF THE ARMY 328–29 (1880) (“[c]onspiracy by two or
    more to violate the laws of war by destroying life or property in aid
    of the enemy” is an “offence[] against the laws and usages of war”).
    That said, although Winthrop based that conclusion in part on the
    Lincoln conspirators’ case, he also relied on Civil War-era field
    orders. WINTHROP, MILITARY LAW AND PRECEDENTS, supra, at
    839 & n.5 (explaining different bases of military jurisdiction and
    43
    Also noteworthy is the World War II-era military
    commission trial of several Nazi saboteurs who entered the
    United States intending to destroy industrial facilities; they
    were convicted of, inter alia, conspiracy to commit violations
    of the law of war. See Quirin, 
    317 U.S. at
    21–23. Although
    the Supreme Court resolved the case on other grounds and
    therefore did not review the validity of the conspiracy
    conviction, the case remains another prominent example of a
    conspiracy charge tried in a law-of-war military commission.
    President Franklin D. Roosevelt, like President Johnson
    before him, approved the charges. See 
    7 Fed. Reg. 5103
    -02
    (July 7, 1942). Moreover, Quirin is not the sole example
    from that era. See Colepaugh v. Looney, 
    235 F.2d 429
    , 431–
    32 (10th Cir. 1956) (upholding conviction by military
    commission of Nazi saboteur of conspiracy to commit offense
    against law of war); General Order (G.O.) No. 52, War Dep’t
    (July 7, 1945) (President Truman approves convictions of
    Colepaugh conspirators), reprinted in Supp. Auth. 149–50;
    Memo. of Law from Tom C. Clark, Assistant Att’y Gen., to
    Major General Myron C. Kramer, Judge Advocate Gen., at 6
    (Mar. 12, 1945), reprinted in Supp. Auth. 139 (opining, with
    regard to Colepaugh case, that “it may be said to be well
    established that a conspiracy to commit an offense against the
    laws of war is itself an offense cognizable by a commission
    administering military justice”). Finally, during the Korean
    War, General Douglas MacArthur ordered that persons
    accused of “conspiracies and agreements to commit . . .
    violations of the laws and customs of war of general
    citing cases of Henry Wirz, William Murphy, G. St. Leger Grenfel
    and others as examples of criminal conspiracies tried by military
    commission on combination of jurisdictional bases). The field
    orders lack the high-level Executive Branch consultation of the
    Lincoln conspirators’ case, however, and give us pause for
    additional reasons discussed infra p. 46.
    44
    application” be tried by military commission. See Letter
    Order, Gen. HQ, United Nations Command, Tokyo, Japan,
    Trial of Accused War Criminals (Oct. 28, 1950) (Rules of
    Criminal Procedure for Military Commissions, Rule 4).
    We do not hold that these precedents conclusively
    establish conspiracy as an offense triable by military
    commission under section 821. After all, four justices
    examined the same precedents and found them insufficiently
    clear. Hamdan, 
    548 U.S. at
    603–09 (plurality);17 cf. Marks v.
    United States, 
    430 U.S. 188
    , 193 (1977). But there are two
    differences between Hamdan and this case. First, the
    elements of the conspiracy charge were not defined by statute
    in Hamdan and therefore the plurality sought precedent that
    was “plain and unambiguous.” 
    548 U.S. at 602
    . Here, the
    Congress has positively identified conspiracy as a war crime.
    We need not decide the effect of the Congress’s action,
    however, because we rely on the second difference: The
    Hamdan plurality’s review was de novo; our review is for
    plain error. We think the historical practice of our wartime
    tribunals is sufficient to make it not “obvious” that conspiracy
    was not traditionally triable by law-of-war military
    commission under section 821. Olano, 
    507 U.S. at 734
    . We
    therefore conclude that any Ex Post Facto Clause error in
    trying Bahlul on conspiracy to commit war crimes is not
    plain. See United States v. Vizcaino, 
    202 F.3d 345
    , 348 (D.C.
    Cir. 2000) (assuming error to decide it was not plain).
    17
    The Hamdan plurality thought Quirin suggested “that
    conspiracy is not a violation of the law of war” because the Court’s
    “analysis . . . placed special emphasis on the completion of [another
    charged] offense; it took seriously the saboteurs’ argument that
    there can be no violation of a law of war—at least not one triable by
    military commission—without the actual commission of . . . a
    ‘hostile and warlike act.’ ” 
    548 U.S. at
    606–07 (plurality).
    45
    B. Material Support
    A different result obtains, however, regarding Bahlul’s
    conviction of providing material support for terrorism.18 The
    Government concedes that material support is not an
    international law-of-war offense, see Oral Arg. Tr. 15; Panel
    Br. of United States 50, 57, and we so held in Hamdan II, 696
    F.3d at 1249–53. But, in contrast to conspiracy, the
    Government offers little domestic precedent to support the
    notion that material support or a sufficiently analogous
    offense has historically been triable by military commission.
    Although Bahlul carries the burden to establish plain error,
    see United States v. Brown, 
    508 F.3d 1066
    , 1071 (D.C. Cir.
    2007), we presume that in the unique context of the “domestic
    common law of war”—wherein the Executive Branch shapes
    the relevant precedent and individuals in its employ serve as
    prosecutor, judge and jury—the Government can be expected
    to direct us to the strongest historical precedents. What the
    Government puts forth is inadequate.
    18
    The 2006 MCA provides: “Any person subject to this
    chapter who provides material support or resources, knowing or
    intending that they are to be used in preparation for, or in carrying
    out, an act of terrorism . . . , or who intentionally provides material
    support or resources to an international terrorist organization
    engaged in hostilities against the United States, knowing that such
    organization has engaged or engages in terrorism . . . , shall be
    punished . . . .” 10 U.S.C. § 950v(b)(25). The provision cross-
    references the Act’s prohibition of “terrorism,” which is defined as
    an act that “kills or inflicts great bodily harm on one or more
    protected persons, or . . . that evinces a wanton disregard for human
    life, in a manner calculated to influence or affect the conduct of
    government or civilian population by intimidation or coercion, or to
    retaliate against government conduct.” Id. § 950v(b)(24).
    46
    The Government relies solely on a number of Civil War-
    era field orders approving military commission convictions of
    various offenses that, the Government contends, are
    analogous to material support. Before delving into the
    specifics of the orders, we note our skepticism that such
    informal field precedent can serve as the sole basis for
    concluding that a particular offense is triable by a law-of-war
    military commission. Unlike the Lincoln conspirators’ and
    Nazi saboteurs’ cases, which attracted national attention and
    reflected the deliberations of highest-level Executive Branch
    officials, the field precedents are terse recordings of
    drumhead justice executed on or near the battlefield. Indeed,
    several precedents cited by the Government for trying
    material support and solicitation under the “law of war” were
    issued by the same 1862 military commission that tried one
    Henry Willing for the offense of “[b]eing a bad and dangerous
    man.” G.O. No. 19, HQ, Dep’t of the Mississippi (Apr. 24,
    1862), 1 THE WAR OF THE REBELLION, OFFICIAL RECORDS OF
    THE UNION AND CONFEDERATE ARMIES (OR) ser. II, at 480–
    81. In addition, the military commissions these orders
    memorialize were not always models of due process.19 And,
    as the Hamdan plurality explained, the Civil War
    commissions “operated as both martial law or military
    government tribunals and law-of-war commissions,” obliging
    us to treat the precedents “with caution” because of their
    unclear jurisdictional basis. 
    548 U.S. at
    596 n.27 (plurality);
    see also 
    id. at 608
    .20
    19
    See Frank J. Williams & Nicole J. Benjamin, Military Trials
    of Terrorists: From the Lincoln Conspirators to the Guantanamo
    Inmates, 39 N. KY. L. REV. 609, 625 (2012); David Glazier,
    Precedents Lost: The Neglected History of the Military
    Commission, 46 VA. J. INT’L L. 5, 39–40 (2005).
    20
    See also Hamdan, 
    548 U.S. at
    602 n.34 (plurality)
    (explaining that because of “vagueness” concerns, “caution . . .
    47
    In any event, even if the law of war can be derived from
    field precedents alone, none of the cited orders charges the
    precise offense alleged here—providing material support for
    terrorism. The Government nonetheless contends that the
    material support charge “prohibits the same conduct, under a
    modern label, as the traditional offense of joining with or
    providing aid to guerrillas and other unlawful belligerents.”
    E.B. Br. of United States 48. But we do not think the cited
    field orders establish that such conduct was tried by law-of-
    war military commissions during the Civil War.21
    First, every precedent cited by the Government involves
    offenses committed in Missouri, a border state; none is from a
    state that seceded. See Dow v. Johnson, 
    100 U.S. 158
    , 164–
    65 (1879) (observing that, during the Civil War, “[t]he people
    of the loyal States . . . and the people of the Confederate
    States . . . became enemies to each other, and . . .
    [c]ommercial intercourse and correspondence between them
    were prohibited . . . by the accepted doctrines of public law”);
    McKinzie v. Hill, 
    51 Mo. 303
    , 307 (1873) (“[T]he principles
    [regarding the duty of “total non-intercourse between the
    belligerents”] have no application to the present case.
    Missouri was not one of the States that joined in the
    rebellion.”). The difference between a border state—whose
    citizens owed a duty of loyalty to the United States—and a
    state that seceded—whose citizens did not—is significant.
    The crime of “aiding the enemy,” which includes as an
    element the breach of a duty of loyalty owed to the United
    States, had long been triable by military commission. See
    must be exercised in the incremental development of common-law
    crimes”); Hamdan II, 696 F.3d at 1250 n.10 (similar).
    21
    In reviewing this Civil War precedent, we hold only that it
    does not sanction trying material support by military commission.
    48
    Hamdan II, 696 F.3d at 1245 n.4 (citing Hamdan, 
    548 U.S. at
    600–01 n.32 (plurality)); WINTHROP, MILITARY LAW AND
    PRECEDENTS, supra, at 839–40 (“offences in violation of the
    laws and usages of war” subject to trial by law-of-war
    military commission include “breaches of the law of non-
    intercourse with the enemy, such as . . . furnishing them with
    money, arms, provisions, medicines, &c”); see also 10 U.S.C.
    § 950v(b)(26) (2006) (codifying offense of aiding enemy to
    include element of “breach of an allegiance or duty to the
    United States”). The orders cited by the Government
    frequently refer to the treasonous nature of the conduct,
    implying a breach of loyalty. See, e.g., G.O. No. 9, HQ,
    Dep’t of the Mississippi (Mar. 25, 1862), 1 OR ser. II, at 465–
    66 (case of John Montgomery); id. at 467 (case of Joseph
    Bollinger); G.O. No. 1, HQ, Dep’t of the Missouri (Jan. 1,
    1862), 1 OR ser. II, at 248 (“[C]ertain acts of a treasonable
    character such as conveying information to the enemy, acting
    as spies, &c., are military offenses triable by military tribunals
    and punishable by military authority.”); see also Young v.
    United States, 
    97 U.S. 39
    , 62 (1877) (“[T]reason is a breach
    of allegiance, and can be committed by him only who owes
    allegiance . . . .” (quotation marks omitted)). The material
    support offense charged here, which lacks a breach of loyalty
    requirement, is plainly distinguishable from the “aiding the
    enemy” precedent.
    Second, several of the cited field orders appear to involve
    offenses more akin to aiding and abetting a law-of-war
    violation. See, e.g., G.O. No. 19, HQ, Dep’t of the
    Mississippi (Apr. 24, 1862), 1 OR ser. II, at 478 (Matthew
    Thompson convicted of “joining with, aiding and assisting [a]
    band [of desperadoes] in the commission of acts of plunder,
    robbery and abuse of the citizens of the State of Missouri”).
    Aiding and abetting is a theory of criminal liability, not a
    stand-alone offense like material support. See Ali, 718 F.3d at
    49
    936. As the Court said in Hamdan II, “aiding and abetting
    terrorism prohibits different conduct, imposes different mens
    rea requirements, and entails different causation standards
    than material support for terrorism.” 696 F.3d at 1252. Thus,
    “[i]f the Government wanted to charge [Bahlul] with aiding
    and abetting terrorism . . . it should have done so.” Id.; see 10
    U.S.C. § 950q(1) (2006) (one who “aids [or] abets” offense
    proscribed by 2006 MCA is punishable as principal).
    Third, other orders appear to involve the offense of
    unlawful belligerency—that is, directly waging guerrilla
    warfare. See, e.g., G.O. No. 15, HQ, Dep’t of the Mississippi
    (Apr. 3, 1862), 1 OR ser. II, at 472–476 (approving
    convictions of several men who each, not “being a soldier
    belonging to any lawfully authorized and organized military
    forces at war with the United States,” “t[ook] up arms as an
    insurgent and commit[ted] acts of hostility against” United
    States military forces); G.O. No. 9, HQ, Dep’t of the
    Mississippi (Mar. 25, 1862), 1 OR ser. II, at 464–65 (William
    Kirk convicted of “belong[ing] to a marauding or guerrilla
    band” that “did unlawfully plunder and take away a certain
    yoke of oxen, wagon and other property”); see also
    Instructions for the Government of Armies of the United
    States in the Field, G.O. No. 100, art. 82 (Apr. 24, 1863);
    WINTHROP, MILITARY LAW AND PRECEDENTS, supra, at 840.
    The upshot is that the Civil War field precedent is too
    distinguishable and imprecise to provide the sole basis for
    concluding that providing material support for terrorism was
    triable by law-of-war military commission at the time of
    Bahlul’s conduct.22 We therefore think it was a plain ex post
    22
    Even the Government is dubious of its argument: Executive
    Branch officials previously acknowledged in prepared
    congressional testimony that “there are serious questions as to
    50
    facto violation—again, assuming without deciding that the
    protection of the Ex Post Facto Clause extends to Bahlul, see
    supra pp. 26–27—to try Bahlul by military commission for
    that new offense. See Collins, 
    497 U.S. at
    42–43. The error
    is prejudicial and we exercise our discretion to correct it by
    vacating Bahlul’s material support conviction. Olano, 
    507 U.S. at
    734–36; see also Casey, 
    343 U.S. at 808
     (vacating
    conviction based on Government’s confession of error);
    United States v. Law, 
    528 F.3d 888
    , 909 (D.C. Cir. 2008)
    (same); cf. Petite, 
    361 U.S. at 531
     (vacating conviction based
    on Government’s motion).23
    whether material support for terrorism or terrorist groups is a
    traditional violation of the law of war.” Legal Issues Regarding
    Military Commissions and the Trial of Detainees for Violations of
    the Law of War: Hearing Before the S. Comm. on Armed Services,
    111th Cong. 12 (2009) (statement of David Kris, Assistant Attorney
    General, National Security Division, Department of Justice); see
    also id. at 9 (statement of Jeh Johnson, General Counsel,
    Department of Defense) (“After careful study, the administration
    has concluded that appellate courts may find that ‘material support
    for terrorism’—an offense that is also found in Title 18—is not a
    traditional violation of the law of war.”).
    23
    Unlike with conspiracy, the Government has not identified a
    pre-existing federal criminal statute that might cure any ex post
    facto aspect of Bahlul’s material support conviction.          The
    Government cites 18 U.S.C. § 2339A, which criminalizes providing
    material support or resources knowing they are to be used in a
    violation of section 2332, but that offense was not made
    extraterritorial until October 26, 2001. See Pub. L. No. 107-56,
    § 805(a)(1)(A), 
    115 Stat. 272
    , 377. Although Bahlul was not
    captured until December 2001, nearly all of the conduct of which
    he was convicted took place before September 11, 2001. The only
    overt act that necessarily occurred after September 11 was Bahlul’s
    research on the economic effects of the attack. The record does not
    reflect, however, whether Bahlul committed that or any other act of
    51
    C. Solicitation
    We also conclude that solicitation of others to commit
    war crimes is plainly not an offense traditionally triable by
    military commission.24 The Government concedes it is not an
    international law-of-war offense. See Oral Arg. Tr. 15; Panel
    Br. of United States 50, 57. The Government contends that
    solicitation “possesses a venerable lineage as an offense
    triable by military commission,” E.B. Br. of United States 50,
    but it cites only two Civil War-era field orders involving three
    defendants in support thereof. It mischaracterizes one of the
    orders, asserting that “a military commission convicted
    Francis Skinner of ‘counsel[ing]’ and ‘invit[ing]’ others to
    destroy a railroad in violation of the law of war,” 
    id.,
     when in
    fact Skinner was acquitted of that offense. See G.O. No. 19,
    HQ, Dep’t of the Mississippi (Apr. 24, 1862), 1 OR ser. II, at
    476–77. And although the other two defendants in the cited
    cases were convicted on charges that resemble the 2006 MCA
    solicitation offense, they were also convicted of personal
    involvement in the crimes they solicited. See id. at 478
    (James Barnes convicted of both “attack[ing] the dwelling-
    house of one Thomas H. Keene . . . and with guns and pistols
    attempt[ing] to murder the occupants of said house” and
    “incit[ing] certain persons unknown to make” that attack);
    G.O. No. 15, HQ, Dep’t of the Mississippi (Apr. 3, 1862), 1
    material support constituting a violation of section 2339A after
    October 26, 2001. This charge, then, is unlike the conspiracy
    charge, where Bahlul expressly conceded and the jury necessarily
    found the two omitted elements.
    24
    The 2006 MCA provides: “Any person subject to this
    chapter who solicits or advises another or others to commit one or
    more substantive offenses triable by military commission under this
    chapter shall . . . be punished . . . .” 10 U.S.C. § 950u.
    52
    OR ser. II, at 475 (Edward Wingfield convicted of both
    “assist[ing] and abet[ting] the said persons in the destruction
    of the track, bridges and buildings of the [North Missouri
    Railroad]” and “incit[ing], induc[ing] and procur[ing] the said
    persons to take up arms and to commit acts of hostility against
    the property of the United States”); cf. Hamdan, 
    548 U.S. at 609
     (plurality).
    As noted, we are skeptical that field orders can be the
    sole basis for military commission jurisdiction over a
    particular offense. See supra p. 46. Moreover, the two field
    orders discussed fall far short of meeting any showing we
    would require. Because solicitation to commit war crimes
    was not an offense triable by law-of-war military commission
    when Bahlul’s conduct occurred, it is a plain ex post facto
    violation—again, assuming without deciding that the
    protection of the Ex Post Facto Clause extends to Bahlul, see
    supra pp. 26–27—to try him by military commission for that
    new offense. See Collins, 
    497 U.S. at
    42–43. The error is
    prejudicial and we exercise our discretion to correct it by
    vacating Bahlul’s solicitation conviction. Olano, 
    507 U.S. at
    734–736; see also Casey, 
    343 U.S. at 808
    ; Law, 
    528 F.3d at 909
    ; cf. Petite, 
    361 U.S. at 531
    .25
    25
    As with material support, we cannot conclude that a pre-
    existing federal statute might cure any ex post facto aspect of
    Bahlul’s solicitation conviction. The Government notes that, when
    Bahlul’s conduct occurred, 
    18 U.S.C. § 373
     criminalized
    solicitation of another person to “engage in conduct constituting a
    felony that has as an element the use, attempted use, or threatened
    use of physical force against property or against the person of
    another.” The Government’s brief does not identify an offense that
    Bahlul solicited, however, which it must do for us to compare the
    elements of a pre-existing criminal offense with the elements of the
    charge under the MCA.
    53
    V. Remaining Issues
    In his brief to the panel, Bahlul raised four challenges to
    his convictions that we have not addressed here. He argued
    that (1) the Congress exceeded its Article I, § 8 authority by
    defining crimes triable by military commission that are not
    offenses under the international law of war, see Br. for Bahlul
    38, Bahlul v. United States, No. 11-1324 (D.C. Cir. Mar. 9,
    2012); (2) the Congress violated Article III by vesting
    military commissions with jurisdiction to try crimes that are
    not offenses under the international law of war, see id. at 39–
    40; (3) his convictions violate the First Amendment, see id. at
    43; and (4) the 2006 MCA discriminates against aliens in
    violation of the equal protection component of the Due
    Process Clause, see id. at 54. We intended neither the en
    banc briefing nor argument to address these four issues. See
    Order, Bahlul v. United States, No. 11-1324 (D.C. Cir. May 2,
    2013) (notifying parties that Equal Protection and First
    Amendment issues are not “within the scope of the rehearing
    en banc”). And with the exception of a few passages
    regarding the first two, we received none from the parties.
    We therefore remand the case to the original panel of this
    Court to dispose of Bahlul’s remaining challenges to his
    conspiracy conviction. See United States v. McCoy, 
    313 F.3d 561
    , 562 (D.C. Cir. 2002) (en banc) (remanding outstanding
    issue to panel).
    For the foregoing reasons, we reject Bahlul’s ex post
    facto challenge to his conspiracy conviction and remand that
    conviction to the panel to consider his alternative challenges
    thereto. In addition, we vacate Bahlul’s convictions of
    providing material support for terrorism and solicitation of
    others to commit war crimes, and, after panel consideration,
    remand to the CMCR to determine the effect, if any, of the
    two vacaturs on sentencing.
    So ordered.
    KAREN LECRAFT HENDERSON, Circuit Judge, concurring:
    I write separately to emphasize, for me, the critical nature of
    the Government’s concession that the Ex Post Facto Clause
    protects Bahlul. Had the Government not conceded the point
    and the Court not decided to act on the concession, cf. Young
    v. United States, 
    315 U.S. 257
    , 258–59 (1942), I would have
    reached a different conclusion. I briefly explain why.
    I. It Is Not “Plain” That the Ex Post Facto Clause
    Protects Bahlul
    “ ‘Plain’ is synonymous with ‘clear’ or, equivalently,
    ‘obvious.’ ” United States v. Olano, 
    507 U.S. 725
    , 734
    (1993). Put another way, “the error must be ‘so plain the trial
    judge and prosecutor were derelict in countenancing it, even
    absent the defendant’s timely assistance in detecting it.’ ”
    United States v. Saro, 
    24 F.3d 283
    , 286 (D.C. Cir. 1994)
    (quoting United States v. Frady, 
    456 U.S. 152
    , 163 (1982)).
    An error meets this high standard only if “its erroneous
    character” is established by “a clear precedent in the Supreme
    Court or this circuit.” United States v. Terrell, 
    696 F.3d 1257
    ,
    1260 (D.C. Cir. 2012). Indeed, “[r]arely do we find an error
    to be plain where ‘this court has not ruled on the question.’ ”
    United States v. Laureys, 
    653 F.3d 27
    , 32–33 (D.C. Cir. 2011)
    (per curiam) (quoting United States v. Thomas, 
    896 F.2d 589
    ,
    591 (D.C. Cir. 1990)); see also United States v. Merlos, 
    8 F.3d 48
    , 51 (D.C. Cir. 1993) (error may be plain even in
    absence of controlling precedent if trial court failed to follow
    “legal norm[ that is] absolutely clear (for example, because of
    the clarity of a statutory provision or court rule)”). To be
    “plain,” the error must be clear or obvious at the time of
    appeal. Henderson v. United States, 
    133 S. Ct. 1121
    , 1130–
    31 (2013); United States v. Miller, 
    738 F.3d 361
    , 372 (D.C.
    Cir. 2013).
    Bahlul contends that his convictions are unconstitutional
    because the 2006 MCA, as applied to him, is an ex post facto
    2
    law. Even assuming that Bahlul is correct, the error is not
    plain because there is no holding by any court that an
    unlawful alien enemy combatant detained abroad is entitled to
    the protections of the Ex Post Facto Clause. Before
    Boumediene, Johnson v. Eisentrager, 
    339 U.S. 763
     (1950),
    and United States v. Verdugo-Urquidez, 
    494 U.S. 259
     (1990),
    “were thought to be the controlling Supreme Court cases on
    the Constitution’s application to aliens abroad.” Rasul v.
    Myers, 
    563 F.3d 527
    , 531 (D.C. Cir. 2009) (per curiam). In
    Eisentrager, the Supreme Court held that the Fifth
    Amendment did not apply to aliens with neither property nor
    presence in the United States. 
    339 U.S. at 784
    . Verdugo-
    Urquidez, relying on Eisentrager, held that the Fourth
    Amendment did not apply to such aliens. 
    494 U.S. at 269
    ,
    273–75. Other Supreme Court opinions similarly suggested
    that the Constitution did not apply outside the sovereign
    United States. Zadyvas v. Davis, 
    533 U.S. 678
    , 693 (2001);
    Kwong Hai Chew v. Colding, 
    344 U.S. 590
    , 597 n.5 (1953);
    United States v. Belmont, 
    301 U.S. 324
    , 332 (1937); United
    States v. Curtiss-Wright Export Corp., 
    299 U.S. 304
    , 318
    (1936). We have followed those precedents consistently,
    recognizing that the Fifth Amendment did not extend beyond
    the boundaries of the United States. See, e.g., Jifry v. FAA,
    
    370 F.3d 1174
    , 1182–83 (D.C. Cir. 2004); 32 Cnty.
    Sovereignty Comm. v. Dep’t of State, 
    292 F.3d 797
    , 799 (D.C.
    Cir. 2002); Harbury v. Deutch, 
    233 F.3d 596
    , 603–04 (D.C.
    Cir. 2000), rev’d on other grounds sub nom. Christopher v.
    Harbury, 
    536 U.S. 403
     (2002); People’s Mojahedin Org. of
    Iran v. U.S. Dep’t of State, 
    182 F.3d 17
    , 22 (D.C. Cir. 1999).
    In Boumediene, the Supreme Court for the first time in
    our history extended a constitutional protection to an alien
    located outside the sovereign territory of the United States.
    
    553 U.S. at 770
    . But the Supreme Court “explicitly confined
    its constitutional holding ‘only’ to the extraterritorial reach of
    3
    the Suspension Clause” and “disclaimed any intention to
    disturb existing law governing the extraterritorial reach of any
    constitutional provisions, other than the Suspension Clause.”
    Rasul, 
    563 F.3d at 529
     (quoting Boumediene, 
    553 U.S. at 795
    ). Indeed, it remains the law of this circuit that, after
    Boumediene, aliens detained at Guantanamo may not invoke
    the protections of the Due Process Clause of the Fifth
    Amendment. See Kiyemba v. Obama, 
    555 F.3d 1022
    , 1026 &
    n.9 (D.C. Cir. 2009) (“due process clause does not apply to
    aliens without property or presence in the sovereign territory
    of the United States” and Guantanamo “is not part of the
    sovereign territory of the United States”), vacated and
    remanded, 
    559 U.S. 131
     (2010), reinstated in relevant part,
    
    605 F.3d 1046
     (D.C. Cir. 2010), cert. denied, 
    131 S. Ct. 1631
    (2011); see also Al-Madhwani v. Obama, 
    642 F.3d 1071
    ,
    1077 (D.C. Cir. 2011); Kiyemba v. Obama, 
    561 F.3d 509
    , 518
    n.4 (D.C. Cir. 2009) (Kavanaugh, J., concurring); Cuban Am.
    Bar Ass’n, Inc. v. Christopher, 
    43 F.3d 1412
    , 1428 (11th Cir.
    1995) (Fifth Amendment does not apply to Cubans and
    Haitians temporarily housed at Guantanamo). Whether
    Boumediene in fact portends a sea change in the
    extraterritorial application of the Constitution writ large, we
    are bound to take the Supreme Court at its word when it limits
    its holding to the Suspension Clause. See Rodriguez de
    Quijas v. Shearson/Am. Express, Inc., 
    490 U.S. 477
    , 480–81
    (1989). Thus, the extraterritorial inapplicability of the Ex
    Post Facto Clause remains as it was before Boumediene.
    Bahlul points to no case from the Supreme Court or any
    court of appeals, nor to any other “absolutely clear” legal
    norm, opining that the Ex Post Facto Clause applies beyond
    the sovereign territory of the United States. Finding such a
    precedent would be a remarkable feat inasmuch as
    Boumediene expressly recognized that it was the first case to
    apply any constitutional provision to aliens located beyond
    4
    our sovereign territory: “It is true that before today the Court
    has never held that noncitizens detained by our Government
    in territory over which another country maintains de jure
    sovereignty have any rights under our Constitution.” 
    553 U.S. at 770
    . Because there is no clear precedent establishing
    that the Ex Post Facto Clause applies to aliens held at
    Guantanamo, prosecuting Bahlul under the 2006 MCA cannot
    constitute plain constitutional error.
    II. The Ex Post Facto Clause Does Not Protect Bahlul
    Even if our review were de novo, I would conclude that
    the Ex Post Facto Clause does not apply to aliens detained at
    Guantanamo. As discussed above, only one constitutional
    protection applies to Guantanamo even after Boumediene.
    
    553 U.S. at 795
     (“Our decision today holds only that
    petitioners before us are entitled to seek the writ.”); see Rasul,
    
    563 F.3d at 529
    . Boumediene is the law and therefore it must
    be followed. But before 2008, the Constitution did not apply
    to aliens without property or presence in the United States.
    After 2008, the Suspension Clause—and only the Suspension
    Clause—protects only those aliens detained on the
    southeastern tip of an island outside the sovereign United
    States.    We have previously said that, “[a]s a novel
    constitutional development, we are loath to expand
    Boumediene’s reach without specific guidance from the
    Supreme Court, particularly where expansion would carry us
    further into the realm of war and foreign policy.” Maqaleh v.
    Hagel, 
    738 F.3d 312
    , 336 n.16 (D.C. Cir. 2013). I see no
    reason to abandon that caution.
    Finally, we must remember the who, what and where of
    this case. Bahlul is an alien unlawful enemy combatant
    who—like Hitler’s Goebbels—led Osama bin Laden’s
    propaganda operation and freely admitted his role in the 9/11
    5
    atrocities. He was tried outside the sovereign United States
    for war crimes. During the post-World War II Nuremberg
    trials several defendants raised ex post facto objections but
    they were rejected as “sheer absurdity” under international
    law. 3 Trials of War Criminals Before the Nuremberg
    Military Tribunals: “The Justice Case” 975 (1951). I cannot
    agree that Bahlul is entitled to domestic constitutional
    protections—to which he would not be entitled under
    international law—simply because his war crimes trial was
    held at an American naval base located in Cuba.
    Accordingly, were it not for the Government’s
    concession that the Ex Post Facto Clause protects Bahlul, I
    would reach the issue and conclude that it does not.1
    1
    Responding briefly to Judge Kavanaugh’s concurrence, and
    with respect, I believe he is a solo source of confusion. He persists
    in reading the majority opinion to resuscitate Hamdan II. Cf.
    Kavanaugh Op. 1. He is wrong. I leave it to the careful reader to
    discern, not surprisingly, that the majority expressly overrules
    Hamdan II’s statutory holding. See Majority Op. 15. Judge
    Kavanaugh then pivots, calling the majority’s decision to
    “ ‘overrule[]’ ” Hamdan II’s “statement” “a meaningless exercise.”
    Kavanaugh Op. 27. Despite his best efforts at revisionism, the fact
    of the matter is that Hamdan II was wrongly decided and today the
    majority so holds.
    ROGERS, Circuit Judge, concurring in the judgment in part
    and dissenting. Ali Hamza Ahmad Suliman al Bahlul, a self-
    avowed member of al Qaeda who has been held in the Naval
    Base at Guantanamo Bay, Cuba since 2002, was convicted and
    sentenced to life imprisonment by a military commission for
    three offenses under the Military Commissions Act of 2006.
    The question before the en banc court is whether these charges
    support the jurisdiction of the military commission. See Order,
    Apr. 23, 2013. Because Bahlul’s conduct occurred prior to the
    enactment of the 2006 Act, and the military commission lacked
    jurisdiction to try these non-law-of-war offenses, Bahlul’s
    convictions must be vacated. The court is vacating Bahlul’s
    convictions for material support and solicitation. For the
    following reasons, I would also vacate Bahlul’s conviction for
    inchoate conspiracy.
    I.
    In Hamdan v. Rumsfeld, 
    548 U.S. 557
    , 590 (2006), the
    Supreme Court observed that “[t]he military commission, a
    tribunal neither mentioned in the Constitution nor created by
    statute, was born of military necessity.” Historically, such
    commissions have been used in three situations. 
    Id. at 595
    (plurality op.); 
    id. at 683
     (Thomas, J., dissenting). First, they
    have substituted for civilian courts where martial law has been
    declared. Second, they have tried civilians in occupied enemy
    territory or territory regained from an enemy where civilian
    government cannot function. Third, military commissions have
    been convened to try “enemies who in their attempt to thwart or
    impede our military effort have violated the law of war.” Ex
    Parte Quirin, 
    317 U.S. 1
    , 28–29 (1942). This third type of
    military commission is designed “to determine, typically on the
    battlefield itself, whether the defendant has violated the law of
    war.” Hamdan, 
    548 U.S. at
    596–97 (plurality op.); cf. 
    id. at 641
    (Kennedy, J., concurring in part). Its jurisdiction is thus limited
    2
    to “offenses cognizable during time of war.” 
    Id. at 596
    (plurality op.); see 
    id. at 641
     (Kennedy, J., concurring in part).
    “Trial by military commission raises separation-of-powers
    concerns of the highest order.” 
    Id. at 638
     (Kennedy, J.,
    concurring in part). “Every extension of military jurisdiction is
    an encroachment on the jurisdiction of the civil courts, and,
    more important, acts as a deprivation of the right to jury trial and
    of other treasured constitutional protections.” Reid v. Covert,
    
    354 U.S. 1
    , 21 (1957) (plurality op.); see 
    id. at 41
     (Frankfurter,
    J., concurring in result); see also THE FEDERALIST NO. 47, at 324
    (James Madison) (J. Cooke ed., 1961) (warning against the
    “tyranny” created through the “accumulation of all powers
    legislative, executive and judiciary in the same hands”). A
    statute conferring judicial power outside the Article III courts
    “may no more lawfully chip away at the authority of the Judicial
    Branch than it may eliminate it entirely. ‘Slight encroachments
    create new boundaries from which legions of power can seek
    new territory to capture.’” Stern v. Marshall, 
    131 S. Ct. 2594
    ,
    2620 (2011) (quoting Reid, 
    354 U.S. at 39
     (plurality op.)). Even
    when confronted with the exigencies of war, “[the Court] cannot
    compromise the integrity of the system of separated powers and
    the role of the Judiciary in that system.” 
    Id.
    The question presented by Bahlul’s appeal is the effect of
    the 2006 Act on these settled principles. Given “the duty which
    rests on the courts, in time of war as well as in time of peace, to
    preserve unimpaired the constitutional safeguards of civil
    liberty,” Quirin, 
    317 U.S. at 19
    , this court must assure itself that
    the military commission had jurisdiction over the charged
    offenses of which Bahlul was convicted. See Hamdan, 
    548 U.S. at
    611–12 (plurality op.); 
    id. at 683
     (Thomas, J., dissenting);
    Application of Yamashita, 
    327 U.S. 1
    , 17–18 (1946); Quirin,
    
    317 U.S. at 25
    ; 10 U.S.C. § 950g(d). The court properly
    considers a challenge to the jurisdiction of a military
    3
    commission at any time it is raised. See R.M.C. 907(b)(1), THE
    MANUAL FOR MILITARY COMMISSIONS, at II-87 (2007) (“A
    charge or specification shall be dismissed at any stage of the
    proceedings if: (A) The military commission lacks jurisdiction
    to try the accused for the offense”); cf. FED. R. CIV. P. 12(h)(3)
    (“If the court determines at any time that it lacks subject-matter
    jurisdiction, the court must dismiss the action”); Arbaugh v.
    Y&H Corp., 
    546 U.S. 500
    , 506 (2006) (“The objection that a
    federal court lacks subject-matter jurisdiction, see FED. R. CIV.
    P. 12(b)(1), may be raised by a party, or by a court on its own
    initiative, at any stage in the litigation, even after trial and the
    entry of judgment.”).
    A.
    Congress enacted the Military Commissions Act of 2006,
    Pub. L. No. 109-366, 
    120 Stat. 2600
    , to authorize the
    establishment of law-of-war military commissions and to
    establish procedures governing their use. The 2006 Act
    specifies the “[c]rimes triable by military commissions,” 10
    U.S.C. § 950v, including offenses such as attacking civilians, id.
    § 950v(b)(2), taking hostages, id. § 950v(b)(7), and torture, id.
    § 950(b)(11). Congress included an unequivocal statement of
    the purpose and effect of its enactment:
    (a) PURPOSE. — The provisions of this subchapter
    codify offenses that have traditionally been triable by
    military commissions. This chapter does not establish
    new crimes that did not exist before its enactment, but
    rather codifies those crimes for trial by military
    commission.
    (b) EFFECT. — Because the provisions of this
    subchapter (including provisions that incorporate
    definitions in other provisions of law) are declarative
    of existing law, they do not preclude trial for crimes
    4
    that occurred before the date of the enactment of this
    chapter.
    Id. § 950p (emphases added). The court must “presume that
    [the] legislature says in a statute what it means and means in a
    statute what it says there.” Conn. Nat’l Bank v. Germain, 
    503 U.S. 249
    , 253–54 (1992). The words used by Congress are to be
    understood in their ordinary, normal meaning, absent a contrary
    indication. See Freeman v. Quicken Loans, Inc., 
    132 S. Ct. 2034
    , 2042 (2012).
    The reference in Congress’s plain and unequivocal
    statement of purpose to “offenses that have traditionally been
    triable by military commissions,” 10 U.S.C. § 950p(a) (emphasis
    added), clearly indicates its intent to confine military
    commissions to their traditional role and jurisdiction, not to
    overturn settled principles. “Traditionally” is the adverbial form
    of the word “traditional,” which means “long-established” or
    “habitually done, used, or found.” THE NEW OXFORD
    AMERICAN DICTIONARY 1785 (2d ed. 2005). A “tradition[]” is
    readily identified and found in established practices; it is not
    based on a “few scattered . . . anomalies.” NLRB v. Noel
    Canning, No. 12-1281, slip op. at 21 (U.S. June 26, 2014). To
    quote Henry James: “[I]t takes an endless amount of history to
    make even a little tradition.” THE AMERICAN SCENE 164 (1907).
    Thus sang Tevye in “Fiddler on the Roof” of “Tradition” that
    has lasted for generations. Jerry Bock & Sheldon Harnick,
    Prologue – Tradition, on FIDDLER ON THE ROOF (RCA Victor
    1964).
    Congress’s unusual “effect” statement, that the 2006 Act’s
    provisions are “declarative of existing law,” 10 U.S.C.
    § 950p(b), amplifies its instruction in the statement of purpose
    to look to offenses traditionally triable by military commissions.
    Here, Congress expresses sensitivity to the implicit
    5
    constitutional concerns arising from authorizing military
    commissions to try persons for conduct predating the 2006 Act.
    Its statement that the 2006 Act permits retroactive application
    only for offenses previously triable by military commission
    accords with the established “presumption against statutory
    retroactivity,” and is the very antithesis of a contrary
    “unambiguous directive” or “express command” requiring
    retroactivity. Landgraf v. USI Film Products, 
    511 U.S. 244
    ,
    263, 270, 280 (1994); see also Calder v. Bull, 
    3 Dall. 386
    , 390
    (1798) (opinion of Chase, J.); Martin v. Hadix, 
    527 U.S. 343
    ,
    354 (1999); Lindh v. Murphy, 
    521 U.S. 320
    , 325 (1997). This
    presumption is “deeply rooted in our jurisprudence, and
    embodies a legal doctrine centuries older than our Republic.”
    Landgraf, 
    511 U.S. at 265
    .
    Ambiguity, if any, would arise, therefore, only in
    identifying the offenses that “have traditionally been triable by
    military commissions,” 10 U.S.C. § 950p(a), and the Supreme
    Court has provided clear guidance on the resolution of this
    question. Congress’s statement that the offenses it has listed are
    “declarative of existing law,” id. § 950p(b), is a legal conclusion
    that is subject to a judicial declaration of what the law is. See
    Marbury v. Madison, 
    5 U.S. 137
    , 177 (1803); see also Noel
    Canning, No. 12-1281, slip op. at 7. “[A] mistaken opinion of
    the legislature concerning the law[] does not make law.”
    Postmaster-General v. Early, 
    25 U.S. 136
    , 148 (1827); see also
    United States v. Stafoff, 
    260 U.S. 477
    , 480 (1923) (Holmes, J).
    Determining what offenses were “traditionally” tried by military
    commissions according to “existing law” at the time of the
    conduct underlying Bahlul’s convictions carries out Congress’s
    expressly stated purpose, and is not an attempt to rewrite the
    2006 Act’s listing of offenses because Congress was mistaken,
    see Op. at 25.
    At the time of Bahlul’s charged conduct, the relevant statute
    6
    was Article 21 of the Uniform Code of Military Justice, 
    10 U.S.C. § 821
     (2000). See Hamdan, 
    548 U.S. at
    592–93; see also
    Yamashita, 
    327 U.S. at 7
    ; Quirin, 
    317 U.S. at 28
    . It confers
    jurisdiction on military commissions over “offenders or offenses
    that by statute or by the law of war may be tried by military
    commissions.” 
    10 U.S.C. § 821
     (2000). The only offenses then
    listed by statute were spying and aiding the enemy, 
    10 U.S.C. §§ 904
    , 906 (2000). Because Bahlul was not charged with either
    of these offenses, the military commission trying him had
    jurisdiction only over violations triable by military commission
    under “the law of war.” See Hamdan, 
    548 U.S. at 613
    ;
    Yamashita, 
    327 U.S. at 17
    ; Quirin, 
    317 U.S. at 29
    .
    For more than seventy years, the Supreme Court has
    interpreted the “law of war” to mean the international law of
    war. In Quirin, examining the predecessor statute to 
    10 U.S.C. § 821
     — Article 15 of the Articles of War, which similarly
    referenced “offenders or offenses that by statute or by the law of
    war may be triable by such military commissions” — the Court
    stated that in Article 15 Congress had “sanction[ed], within
    constitutional limitations, the jurisdiction of military
    commissions to try persons and offenses which, according to the
    rules and precepts of the law of nations, and more particularly
    the law of war, are cognizable by such tribunals.” 
    317 U.S. at
    27–28 (emphasis added).            The Court reaffirmed its
    understanding that the law of war is a “branch of international
    law,” 
    id. at 29
    , four years later in Yamashita. Discussing the
    jurisdiction of the military commission, the Court looked to the
    violations of the law of war “recognized in international law”
    and consulted the Hague Conventions and the Geneva
    Conventions. Yamashita, 
    327 U.S. at
    14–16. “[W]hen a new
    legal regime develops out of an identifiable predecessor, it is
    reasonable to look to the precursor in fathoming the new law.”
    Johnson v. United States, 
    529 U.S. 694
    , 710 (2000); see also
    Hamilton v. Rathbone, 
    175 U.S. 414
    , 421 (1899). More
    7
    recently, in addressing Section 821 in Hamdan, the Court
    adhered to Quirin and Yamashita by looking to the body of
    international law governing armed conflict. See Hamdan, 
    548 U.S. at
    602–03 (plurality op.); 
    id. at 641
     (Kennedy, J.,
    concurring in part); see also Memorandum from the Office of
    Legal Counsel to the Attorney General 28, 30 (July 16, 2010),
    printed in New York Times v. United States, No. 13-422-cv, slip
    op. app. A (2d Cir. June 23, 2014) (describing the law of war as
    international law).
    B.
    To demonstrate that the offenses of which Bahlul was
    convicted are violations of the international law of war and
    within the jurisdiction of his military commission, Supreme
    Court precedent indicates that the “Government must make a
    substantial showing that the crime for which it seeks to try a
    defendant by military commission is acknowledged to be an
    offense against the law of war.” Hamdan, 
    548 U.S. at 603
    (plurality op.). For instance, in Quirin, the Court concluded that
    a military commission had jurisdiction to try “unlawful
    combatants” who surreptitiously entered the United States,
    discarding their uniforms on arrival, for the purpose of
    committing hostile acts involving destruction of life or property.
    
    317 U.S. at
    35–36. This charge, the Court explained, “has been
    so recognized in practice both here and abroad, and has so
    generally been accepted as valid by authorities on international
    law that we think it must be regarded as a rule or principle of the
    law of war.” 
    Id.
     Similarly, in Yamashita, the Supreme Court
    held that a military commission had jurisdiction to try an
    invading Commanding General of the Imperial Japanese Army
    for breach of his duty to control the members of his command,
    by permitting them to commit atrocities against civilian
    populations and prisoners of war, because the charge “plainly”
    alleged a violation of the law of war, the purpose of which is “to
    protect civilian populations and prisoners of war from brutality.”
    8
    
    327 U.S. at
    13–18.
    The government has repeatedly conceded that the three
    offenses of which Bahlul was convicted are not, and were not at
    the time of Bahlul’s conduct, law-of-war offenses under
    international law. See Resp’t’s Br. 34 (regarding conspiracy
    only); Resp’t’s Pet. for Reh’g En Banc 1–2 (“the charges are not
    sustainable under Hamdan II because they have not attained
    recognition at this time as offenses under customary international
    law”); Resp’t’s pre-Hamdan II Panel Br. 57 (“the offenses of
    conspiracy, solicitation, and providing material support to
    terrorism have not attained international recognition at this time
    as offenses under customary international law”); Oral Argument
    Tr. 15 (Sept. 30, 2013) (“we have conceded that [all three
    offenses] are not violations of the international law of war”).
    This should end the matter given Congress’s stated purpose and
    effect in the 2006 Act, 10 U.S.C. § 950p. Instead, departing
    from the instruction of more than half a century of Supreme
    Court precedent, the government contends that the en banc court
    can affirm Bahlul’s convictions on the basis of a U.S. common
    (or U.S. domestic) law of war. Because the court is vacating
    Bahlul’s convictions for material support for terrorism and
    solicitation but not for inchoate conspiracy, see Op. at 3, I need
    address only Bahlul’s jurisdictional challenges to his conviction
    for inchoate conspiracy. It bears noting, however, that the
    court’s analysis of the infirmities of the government’s U.S.
    common law theory, based on Civil War military commissions
    and field orders, in vacating two of Bahlul’s convictions applies
    no less to his conviction for inchoate conspiracy. See Op. at 46,
    49, 52.
    1. The trial record of the law-of-war military commission
    makes clear Bahlul was charged and convicted of inchoate
    conspiracy; his stand-alone conspiracy conviction did not depend
    upon proof of the completion of any object offense (such as
    9
    murder) or proof that the overt acts in furtherance of the
    conspiratorial agreement of which he was convicted (such as
    preparing a propaganda video) were law-of-war offenses.
    First, the government elected not to charge Bahlul under the
    Pinkerton doctrine under which he could have been found
    vicariously liable for reasonably foreseeable substantive crimes
    committed by his co-conspirators in furtherance of the
    conspiracy. See Resp’t’s Br. 47; Pinkerton v. United States, 
    328 U.S. 640
     (1946). The government also did not pursue the theory
    that Bahlul had joined a joint criminal enterprise. At the
    beginning of Bahlul’s trial, the prosecutor moved to strike the
    charge that Bahlul had “join[ed] al Qaeda, an enterprise of
    persons who share the common criminal purpose that involved,
    at least in part, the commission or intended commission of one
    or more substantive offenses triable by military commission.”
    Trial Tr. 110.
    Second, the trial evidence allowed for conviction of no more
    than inchoate conspiracy. The government’s evidence consisted
    of Bahlul’s agreement with Usama bin Laden and other members
    of al Qaeda to commit law-of-war offenses and his commission
    of non-law-of-war, non-criminal overt acts in furtherance of the
    agreement. (The government’s focus at trial was on Bahlul’s
    role as an al Qaeda propagandist, in particular, his preparation of
    a recruitment video entitled “The Destruction of the American
    Destroyer U.S.S. Cole.”) None of the overt acts committed in
    furtherance of the charged conspiracy — including traveling to
    Afghanistan with the intent to join al Qaeda, undergoing
    military-type training at a training camp sponsored by al Qaeda,
    pledging fealty (or “bayat”) to Usama bin Laden, or transcribing
    the martyr wills of two of the September 11th hijackers — is a
    law-of-war offense. Even assuming being armed would have
    sufficed, the military commission found Bahlul not guilty of the
    overt act that he had “armed himself with an explosive belt, rifle,
    10
    and grenades to protect and prevent the capture of Usama bin
    Laden.”
    Third, the presiding military judge instructed the members
    of the military commission that to find Bahlul guilty of
    conspiracy, they must find beyond a reasonable doubt that he
    knowingly entered into an agreement to commit one or more
    substantive offenses triable by military commission and that he
    knowingly committed at least one overt act in furtherance of that
    agreement. Trial Tr. 845–46. The judge further instructed that
    proof the object of the conspiratorial agreement, the substantive
    law-of-war offense, “actually occurred is not required” and
    “[t]he overt act required for this offense does not have to be a
    criminal act.” 
    Id.
     at 848–49. The presiding judge also confirmed
    that Bahlul was not being tried on the basis of a joint criminal
    enterprise; when he discovered that his written instructions
    included the word “enterprise,” the judge instructed the military
    commission members to strike the words “or enterprise,”
    explaining “that’s not before you,” id. at 881.
    2. The international law of war does not recognize inchoate
    conspiracy as a law-of-war offense. Although there are two
    exceptions — conspiracy to commit genocide and conspiracy to
    wage aggressive war (also known as the commission of crimes
    against peace), see Hamdan, 
    548 U.S. at 610
     (plurality op.); 22
    TRIAL OF THE MAJOR WAR CRIMINALS BEFORE THE
    INTERNATIONAL MILITARY TRIBUNAL: NUREMBERG, 14
    NOVEMBER 1945 – 1 OCTOBER 1946, at 469 (1948) (“TRIAL OF
    MAJOR WAR CRIMINALS AT NUREMBERG”); Antonio Cassese,
    International Criminal Law 191 (2003); see also Br. of Amici
    Curiae Int’l Law Scholars 12–14 — the government does not
    argue that either applies to Bahlul.
    Treaty law and international courts and tribunals have
    refused to recognize inchoate conspiracy as a war crime because
    11
    of its potential for conflict with the international law-of-war
    principle “that criminal guilt is personal, and that mass
    punishments should be avoided.” TRIAL OF MAJOR WAR
    CRIMINALS AT NUREMBERG at 500. Morever, the Anglo-
    American concept of conspiracy is not known to some European
    legal systems. See Telford Taylor, THE ANATOMY OF THE
    NUREMBERG TRIALS: A PERSONAL MEMOIR 36 (1992)
    (“Taylor”). Neither the Hague Conventions nor the Geneva
    Conventions, which are the “major treaties on the law of war,”
    includes inchoate conspiracy as an international law-of-war
    offense. Hamdan, 
    548 U.S. at
    603–04 (plurality op.); see
    Convention with Respect to the Laws and Customs of War on
    Land, July 29, 1899, 
    32 Stat. 1803
    , 1 Bevans 247; Convention
    Respecting the Laws and Customs of War on Land, Oct. 18,
    1907, 
    36 Stat. 2277
    , 1 Bevans 631; Geneva Convention for the
    Amelioration of the Condition of the Wounded and Sick in
    Armed Forces in the Field, Aug. 12, 1949, 6 U.S.T. 3114, 75
    U.N.T.S. 31; Geneva Convention for the Amelioration of the
    Condition of Wounded, Sick and Shipwrecked Members of
    Armed Forces at Sea, Aug. 12, 1949, 6 U.S.T. 3217, 75 U.N.T.S.
    85; Geneva Convention Relative to the Treatment of Prisoners of
    War, Aug. 12, 1949, 6 U.S.T. 3316, 75 U.N.T.S. 135; Geneva
    Convention Relative to the Protection of Civilian Persons in
    Time of War, Aug. 12, 1949, 6 U.S.T. 3516, 75 U.N.T.S. 287;
    Protocol Additional to the Geneva Conventions of 12 August
    1949, and Relating to the Protection of Victims of International
    Armed Conflicts, June 8, 1977, 1125 U.N.T.S. 3; Protocol
    Additional to the Geneva Conventions of 12 August 1949, and
    Relating to the Protection of Victims of Non-International
    Armed Conflicts, June 8, 1977, 1125 U.N.T.S. 609.
    The International Military Tribunal convened at Nuremberg
    “pointedly refused to recognize as a violation of the law of war
    conspiracy to commit war crimes,” Hamdan, 
    548 U.S. at 610
    (plurality op.), concluding that its charter “does not define as a
    12
    separate crime any conspiracy except the one to commit acts of
    aggressive war.” TRIAL OF MAJOR WAR CRIMINALS AT
    NUREMBERG at 469; see also Charter of the International
    Military Tribunal, in Agreement for the Prosecution and
    Punishment of the Major War Criminals of the European Axis,
    Aug. 8, 1945, 
    59 Stat. 1544
    , 82 U.N.T.S. 280; Taylor at 550–53.
    The Charter addressed the personal responsibility of the major
    war criminals of the European Axis. See Charter arts. 1, 6–8.
    The Tribunal was concerned that “overbroad application of the
    conspiracy principle may drag innocent people into the
    prosecution’s net.” Taylor at 553. The United States Military
    Tribunals convened to try additional defendants also concluded
    that they “ha[d] no jurisdiction to try any defendant upon a
    charge of conspiracy considered as a separate substantive
    offense.” 15 UNITED NATIONS WAR CRIMES COMMISSION, LAW
    REPORTS OF TRIALS OF WAR CRIMINALS 90 (1949) (“LAW
    REPORTS OF TRIALS OF WAR CRIMINALS”). In addition, the
    Charter of the International Military Tribunal for the Far East did
    not confer jurisdiction over inchoate conspiracies to commit war
    crimes or crimes against humanity, only conspiracy to commit
    crimes against peace. See Charter of the International Military
    Tribunal for the Far East art. 5, Jan. 19, 1946, T.I.A.S. No. 1589,
    4 Bevans 20.
    Modern statutes defining international law-of-war offenses
    do not refer to conspiracy to commit such offenses (other than
    genocide). See Rome Statute of the International Criminal
    Court, July 17, 1998, 2187 U.N.T.S. 90; Statute of the
    International Tribunal for the Former Yugoslavia, adopted by
    S.C. Res. 827, U.N. Doc. S/RES/827 (1993), reprinted in 32
    I.L.M. 1159, 1192; Statute of the International Tribunal for
    Rwanda, adopted by S.C. Res. 955, U.N. Doc. S/RES/955
    (1994), reprinted in 33 I.L.M. 1598, 1602; Statute of the Special
    Court for Sierra Leone, Jan. 16, 2002, 2178 U.N.T.S. 138.
    Additionally, international tribunals recognizing “joint criminal
    13
    enterprise” as a theory of liability for completed law-of-war
    offenses have rejected a separate inchoate offense based on
    “mere membership” or “conspiring to commit crimes,” and
    instead recognize liability only for “participation in the
    commission of the crime.” Prosecutor v. Milutinovic, Case No.
    IT-99-37-AR72, Decision on Dragoljub Ojdanic’s Motion
    Challenging Jurisdiction – Joint Criminal Enterprise, ¶ 26 (Int’l
    Crim. Trib. for the Former Yugoslavia, Appeals Chamber, May
    21, 2003); Rwamakuba v. Prosecutor, Case No. ICTR-98-44-
    AR72.4, Decision on Interlocutory Appeal Regarding
    Application of Joint Criminal Enterprise to the Crime of
    Genocide, ¶ 30 (Oct. 22, 2004); see also Br. of Amici Curiae
    Int’l Law Scholars 8–10.
    3. Given this historical background, the government has a
    heavy burden to show that Congress’s purpose in enacting the
    2006 Act extended to inchoate conspiracy as an “offense[] that
    ha[s] traditionally been triable by military commissions,” 10
    U.S.C. § 950p(a). The government begins by suggesting that “a
    systemized body of international law establishing individual
    criminal responsibility for specific acts during warfare”
    commenced with the Hague Conventions of 1899 and 1907 and
    “is a relatively modern innovation.” Resp’t’s Br. 28 (citing
    Timothy L.H. McCormack, From Sun Tzu to the Sixth
    Committee: The Evolution of an International Criminal Law
    Regime, in THE LAW OF WAR CRIMES: NATIONAL AND
    INTERNATIONAL APPROACHES 31, 43 (Timothy L.H. McCormack
    & Gerry J. Simpson eds., 1997)). It continues by citing Colonel
    William Winthrop, referred to by the Supreme Court as the
    “Blackstone of Military Law,” Hamdan, 
    548 U.S. at 597
    (plurality op.) (quoting Reid, 
    354 U.S. at
    19 n.38 (plurality op.)),
    for the proposition that prior to the adoption of these and later
    treaties, the “offenses in violation of the laws and usages of war
    [consisted of] those principally, in the experience of our wars,
    made the subject of charges and trial.” Resp’t’s Br. 29 (quoting
    14
    William Winthrop, MILITARY LAW AND PRECEDENTS 839 (1920)
    (“Winthrop PRECEDENTS”)). It also points to the reference in
    Hamdan to “the American common law of war,” 
    548 U.S. at 613
    . Resp’t’s Br. 32. Neither Winthrop nor Hamdan advance
    the government’s case for sustaining Bahlul’s conspiracy
    conviction.
    First, in discussing the Civil War military commissions
    relied upon by the government, Winthrop “excludes conspiracy
    of any kind from his own list of offenses against the law of war.”
    Hamdan, 
    548 U.S. at 608
     (plurality op.) (citing Winthrop
    PRECEDENTS at 839–40). Instead, Winthrop classifies the
    relevant Civil War conspiracy cases either as “[c]rimes and
    statutory offenses cognizable by State or U.S. courts, and which
    would properly be tried by such courts if open and acting,” or as
    a “combin[ation]” of such civilian crimes and “violations of the
    laws and usages of war cognizable by military tribunals.”
    Winthrop PRECEDENTS at 839 & n.5. Winthrop rejected the idea
    that inchoate conspiracy could be triable by law-of-war military
    commission, emphasizing that “the jurisdiction of the military
    commission should be restricted to cases of offence consisting in
    overt acts, i.e. in unlawful commissions or actual attempts to
    commit, and not in intentions merely.” Id. at 841. In other
    words, “‘overt acts’ constituting war crimes are the only proper
    subject at least of those military tribunals not convened to stand
    in for local courts,” Hamdan, 
    548 U.S. at 608
     (plurality op.)
    (citing Winthrop PRECEDENTS at 841 & nn.22, 23). The cases
    cited by the government reveal that this is the manner in which
    the Civil War military commissions proceeded. See infra pt.
    I.C.1.
    Second, the Supreme Court’s reference to “the American
    common law of war” in Hamdan, 
    548 U.S. at 613
    , is to U.S.
    military commission tradition and practice as an additional
    constraint on, not an alternative basis for, military commission
    15
    jurisdiction under Section 821. The Court stated that the
    Uniform Code of Military Justice, which includes Section 821,
    “conditions the President’s use of military commissions on
    compliance not only with the American common law of war, but
    also with the rest of the [Uniform Code of Military Justice] itself,
    insofar as applicable, and with the ‘rules and precepts of the law
    of nations.’” 
    Id.
     (quoting Quirin, 
    317 U.S. at 28
    ). To come
    within the “law of war” under Section 821, an offense must
    constitute both a violation of the international law of war and a
    violation of the law of war as traditionally recognized in U.S.
    military commissions. This is necessary because, as the Court
    explained in Quirin, there may be
    acts regarded in other countries, or by some writers on
    international law, as offenses against the law of war
    which would not be triable by military tribunal here,
    either because they are not recognized by our courts as
    violations of the law of war or because they are of that
    class of offenses constitutionally triable only by a jury.
    
    317 U.S. at 29
    . Consequently, in Quirin, Yamashita, and
    Hamdan the Supreme Court sought to establish that the relevant
    offense was a violation of the law of war under international law
    and was recognized in U.S. military commissions. See Quirin,
    
    317 U.S. at 35
    ; Yamashita, 
    327 U.S. at
    15–16; Hamdan, 
    548 U.S. at 603
     (plurality op.). Under these precedents, the practice of
    U.S. domestic military commissions is irrelevant as long as
    inchoate conspiracy is not an international law-of-war offense,
    and the government conceded that it is not. Of course, to the
    extent the government relies on the Military Commissions Act
    of 2009, which refers to offenses that have “traditionally been
    triable under the law of war or otherwise triable by military
    commission” to support its argument that the statute embraces “a
    class of offenses — lawfully triable in U.S. military commission
    practice — that is broader than the group of offenses that are
    16
    currently prohibited by the international law of war,” Resp’t’s
    Br. 28 (quoting 10 U.S.C. § 950p(d) (2009) (emphasis added)),
    this cannot advance its position since Bahlul was tried under the
    2006 Act.
    The legislative history of the 2006 Act also does not
    advance the government’s position. The Report of the House
    Armed Services Committee on H.R. 6054 states “[f]or the
    reasons stated in Justice Thomas’s opinion [in Hamdan], the
    Committee views conspiracy [to commit a war crime] as a
    separate offense punishable by military commissions.” H.R.
    REP. NO. 109-664, pt. 1, at 25 (2006). But Justice Thomas
    expressly acknowledged that “conspiracy” was understood as a
    law-of-war offense only when it went “beyond ‘intentions
    merely,’” and involved “unlawful” overt acts, 
    548 U.S. at 703
    (Thomas, J., dissenting). There was no occasion in Hamdan for
    Justice Thomas to address the validity of a conspiracy charge
    where, as in Bahlul’s case, “the overt act required . . . does not
    have to be a criminal act,” Trial Tr. 849; Justice Thomas
    observed that Hamdan was “charged with the overt acts of
    providing protection, transportation, weapons, and other services
    to the enemy, acts which in and of themselves are violations of
    the laws of war,” 
    548 U.S. at 704
     (citation omitted).
    C.
    Even assuming, contrary to Supreme Court precedent, that
    a U.S. common law of war tradition could serve as an
    independent basis for sustaining convictions by law-of-war
    military commissions for offenses that are not recognized under
    the international law of war or by then-existing statute, the
    government fails to establish a domestic tradition to sustain
    Bahlul’s inchoate conspiracy conviction. It not only fails to
    point to evidence comparable to the abundance of evidence “both
    here and abroad” relied upon by the Supreme Court in Quirin,
    
    317 U.S. at
    31–35 & nn.10, 12, the government has not identified
    17
    a single case where military commission jurisdiction has been
    sustained on the basis of a charge of inchoate conspiracy, much
    less a charge of conspiracy with instructions defining the limits
    of the government’s burden of proof that are comparable to those
    in Bahlul’s case.
    1. The Civil War cases to which the government points are,
    in fact, consistent with Winthrop’s position. Further, as the
    Supreme Court cautioned, “[t]he Civil War precedents must . . .
    be considered with caution” because military commissions
    “operated as both martial law or military government tribunals
    and law-of-war commissions” and thus “often charged hybrid
    crimes mixing elements of crimes ordinarily triable in civilian
    courts (like treason) and violations of the law of war.” Hamdan,
    
    548 U.S. at
    596 n.27, 609 n.37 (plurality op.); see also Winthrop
    PRECEDENTS at 839 & n.5. For example, William Murphy, who
    was tried by military commission in 1865, was charged with
    “[c]onspiracy to burn and destroy steamboats and other property”
    and also with “[v]iolati[ng] the laws and customs of war,” by in
    fact burning and destroying a steamboat and by secretly crossing
    enemy lines and attempting to destroy a second boat. G.C.M.O.
    No. 107 (1866). These separate charges suggest that Murphy
    was tried by a tribunal serving as both a martial law court and a
    law-of-war military commission, and that the military
    commission classified the conspiracy charge as a civil crime, not
    as a “violation of the laws and customs of war.” 
    Id.
     Only this
    understanding is consistent with the fact that Murphy’s
    conspiracy conviction was vacated because the civil courts were
    open and therefore the military commission “had no jurisdiction
    of his person or of his offence.” In re Murphy, 
    17 F. Cas. 1030
    ,
    1031, 1032 (1867). And because Murphy did in fact destroy a
    steamboat during wartime, his case provides no support for the
    government’s theory that a Civil War military tribunal had
    jurisdiction over conspiracy absent proof, much less absent any
    allegation, of a completed substantive law-of-war offense.
    18
    Similarly, the case of Henry Wirz, also cited by the
    government, does not provide evidence of a tradition on which
    to base affirmance of Bahlul’s inchoate conspiracy conviction.
    Confederate Army Captain Wirz was charged with conspiring to
    injure the health and destroy the lives of soldiers in the military
    service of the United States and “alleged to have personally
    committed a number of atrocities against his victims, including
    torture, injection of prisoners with poison, and use of ‘ferocious
    and bloodthirsty dogs’ to ‘seize, tear, mangle, and maim the
    bodies and limbs’ of prisoners, many of whom died as a result.”
    Hamdan, 
    548 U.S. at 609
     (plurality op.) (citing H.R. Doc. No.
    314, 55th Cong., 3d Sess., 785, 789–90 (1899)). Notably, as the
    Hamdan plurality explained, the Judge Advocate General
    determined that one of Wirz’s alleged co-conspirators, R.B.
    Winder, should not be tried by military commission because
    “while the evidence at the trial of Wirz was deemed by the court
    to implicate him in the conspiracy against the lives of all Federal
    prisoners in rebel hands, no such specific overt acts of violation
    of the laws of war are as yet fixed upon [Winder].” 
    Id.
     (quoting
    H.R. Doc. No. 314, 55th Cong., 3d Sess., 783 (1899)) (emphasis
    in original opinion). In other words, had Wirz not committed
    overt acts that were violations of the law of war, he could not
    have been tried by military commission for conspiracy.
    The 1865 trial of the Lincoln assassins, “even if properly
    classified as a trial by law-of-war commission,” Hamdan, 
    548 U.S. at
    604 n.35 (plurality op.), likewise does not support the
    government’s theory of a U.S. common law-of-war tradition.
    The defendants were charged with both “conspiring” to murder
    President Lincoln and the completed offense of “maliciously,
    unlawfully, and traitorously murdering the said Abraham
    Lincoln,” G.C.M.O. No. 356 (1865); see Hamdan, 
    548 U.S. at
    604 n.35 (plurality op.) (quoting H.R. Doc. 314, 55th Cong., 3d
    Sess., 696 (1899)); see also THE TRIAL: THE ASSASSINATION OF
    PRESIDENT LINCOLN AND THE TRIAL OF THE CONSPIRATORS
    19
    246–47 (Edward Steers, Jr. ed., 2003). Of utmost significance,
    surely, the then-Attorney General, in defending the use of a
    military tribunal, treated the charge as alleging the substantive,
    completed “offence of having assassinated the President.” 11
    Op. Atty. Gen. 297, 297 (1865). Furthermore, the district court,
    in rejecting petitions for a writ of habeas corpus filed by three of
    the assassins, described the charge of conviction as “a conspiracy
    to commit the military crime [of the assassination of the
    Commander in Chief] which one of their number did commit.”
    Ex Parte Mudd, 
    17 F. Cas. 954
     (S.D. Fla. 1868) (emphasis
    added). Recall that in Bahlul’s case the prosecution dismissed
    charges and theories of vicarious liability.
    In sum, the Civil War conspiracy cases, including the trial
    of the Lincoln assassins, each, in fact, involved a completed law-
    of-war offense, not an inchoate conspiracy. These cases are
    consistent with Winthrop’s description of such conspiracies as
    among the “[c]rimes and statutory offenses . . . which would
    properly be tried by [State or U.S.] courts if open and acting,” or
    alternatively, as hybrid crimes combining elements of crimes
    ordinarily triable in civilian courts and law-of-war offenses.
    Winthrop PRECEDENTS at 839 & n.5. They offer no reason to
    depart from Winthrop’s contemporary rejection of inchoate
    conspiracy as a law-of-war offense.
    2. The World War II cases cited by the government also do
    not establish historical support for the jurisdiction of law-of-war
    military commissions over inchoate conspiracy. Although the
    Nazi saboteurs in Quirin were charged with conspiracy, the
    Supreme Court affirmed their convictions based on the
    independent charge that they had violated the law of war by
    crossing behind enemy lines having removed their uniforms,
    with the purpose of committing sabotage. See Quirin, 
    317 U.S. at 48
    . “The offense was complete when with [hostile] purpose
    they entered — or, having so entered, they remained upon — our
    20
    territory in time of war without uniform or other appropriate
    means of identification.” 
    Id. at 38
    . Like the case of the Lincoln
    conspirators, Quirin involved a completed law-of-war offense,
    not an inchoate conspiracy conviction like Bahlul’s. “If
    anything, Quirin supports [the] argument that conspiracy is not
    a violation of the law of war,” because “[t]he Court was careful
    in its decision to identify an overt, ‘complete’ act” and “took
    seriously the saboteurs’ argument that there can be no violation
    of law of war — at least not one triable by military commission
    — without the actual commission or attempt to commit a ‘hostile
    and warlike act.’” Hamdan, 
    548 U.S. at
    606–07 (plurality op.)
    (quoting Quirin, 
    317 U.S. at
    37–38). Brigadier General Mark
    Martins, the Chief Prosecutor of Military Commissions in the
    Department of Defense since June 2011, likewise characterized
    Quirin as an authority “supporting [the] rationale” that
    conspiracy may be tried under the law of war in conjunction with
    a completed offense that appears on the charge sheet, but not as
    an inchoate offense. Memorandum from Mark S. Martins, Chief
    Prosecutor of Military Commissions, Dep’t of Defense, to the
    Convening Authority 4 (Jan. 6, 2013).
    The government’s reliance on Colepaugh v. Looney, 
    235 F.2d 429
     (10th Cir. 1956), is misplaced. The Tenth Circuit
    followed Quirin in affirming the denial of a habeas petition filed
    by another World War II saboteur. Colepaugh had been
    convicted on three charges: (1) he “secretly passed through, in
    civilian dress, contrary to the law of war, the military and naval
    lines of the United States for the purpose of committing
    espionage, sabotage and other hostile acts;” (2) he “appeared and
    remained in civil dress, contrary to the law of war behind the
    military lines of the United States for the purpose of committing
    espionage, sabotage and other hostile acts;” and (3) “conspiracy
    to commit the above substantive offenses.” 
    Id. at 431
    . Like the
    Supreme Court in Quirin, the Tenth Circuit looked to the “body
    of international common law known as the law of war,” 
    id.
     at
    21
    431–32, and concluded that Colepaugh was not entitled to relief
    because he had committed the same substantive law-of-war
    offense as the saboteurs in Quirin when he entered this country
    and discarded his uniform for the purpose of committing hostile
    acts involving the destruction of life or property, 
    id. at 432
    (quoting Quirin, 
    317 U.S. at 35
    ). The court also followed the
    Supreme Court in not confirming the validity of the separate
    conspiracy charge. Consequently, this case, like Quirin,
    provides no support for the government’s theory that Bahlul
    could be tried by military commission for inchoate conspiracy
    absent any charge that he committed a substantive law-of-war
    offense.
    3. In sum, “[f]ar from making the requisite substantial
    showing, the Government has failed even to offer a ‘merely
    colorable’ case for inclusion of conspiracy among those offenses
    cognizable by law-of-war military commission,” Hamdan, 
    548 U.S. at 611
     (plurality op.) (citation omitted). As the plurality in
    Hamdan explained:
    The crime of ‘conspiracy’ has rarely if ever been tried
    as such in this country by any law-of-war military
    commission not exercising some other form of
    jurisdiction, and does not appear in either the Geneva
    Conventions or the Hague Conventions — the major
    treaties on the law of war. Winthrop explains that
    under the common law governing military
    commissions, it is not enough to intend to violate the
    law of war and commit overt acts in furtherance of that
    intention unless the overt acts either are themselves
    offenses against the law of war or constitute steps
    sufficiently substantial to qualify as an attempt.
    
    Id.
     at 603–04 (citing Winthrop PRECEDENTS at 841).
    22
    Insofar as the government proposes, contrary to Supreme
    Court precedent, a U.S. common law of war basis for sustaining
    Bahlul’s conspiracy conviction, the government’s proposal is
    also “unmoored from any enumerated power and has no rational
    stopping place.” Pet’r’s Br. 32. Such a theory suggests that
    modern military commissions could try defendants for any
    offense that approximates a charge previously brought before
    any type of military tribunal, including Civil War era military
    commissions convened to try ordinary civilian crimes. See 
    id.
    The government’s interpretation of Congress’s intent in
    enacting the 2006 Act, additionally, leaves no room for
    consideration of the reasons the international community has
    rejected inchoate crimes as law-of-war offenses: for example,
    their dragnet effect could sweep in and condemn as war
    criminals the line soldier who merely pledged allegiance to the
    enemy as well as the errant but innocent delivery boy or
    shepherd who was on the wrong street at the wrong time. See
    Taylor at 553; Br. of Amicus Curiae Int’l Law Scholars 7, 15–18.
    The Supreme Court has long understood the role of military
    commissions to arise from the military necessity in the midst of
    war “to seize and subject to disciplinary measures those enemies
    who in their attempt to thwart or impede our military effort have
    violated the law of war,” Quirin, 
    317 U.S. at
    28–29; Hamdan,
    
    548 U.S. at 596
     (plurality op.), not to try and convict (as distinct
    from holding as prisoners of war) anyone who is a member of the
    opposing forces. The law of war governing the use of military
    commissions is a product of the costly lessons learned in the last
    century from two World Wars, including the principle that, as a
    matter of international law, law-of-war offenses are about
    personal responsibility for war crimes, not collective guilt. See
    TRIAL OF MAJOR WAR CRIMINALS AT NUREMBERG at 500. It
    seems unlikely the Congress that enacted the 2006 Act intended
    to cast aside such costly learning without expressly indicating
    that it intended to do so; by using the phrase “offenses that have
    23
    traditionally been triable,” 10 U.S.C. § 950p(a) (emphasis
    added), in stating its purpose, Congress signaled it was adhering
    to the established understanding of the role of military
    commissions, not breaking new ground.
    And, even assuming arguendo that practices of U.S. military
    commissions could provide an independent basis upon which to
    support the jurisdiction of a law-of-war commission to try an
    offense not recognized in international law, nor codified in
    statute at the time, the government’s failure to demonstrate that
    such a “tradition[]” existed at the time of the charged conduct
    requires vacatur of Bahlul’s inchoate conspiracy conviction.
    Were the implications for the separation of powers raised by
    trial by military commission not “of the highest order,” Hamdan,
    
    548 U.S. at 638
     (Kennedy, J., concurring in part), the
    government’s effort to establish its inchoate conspiracy theory on
    the basis of so meager and deficient an historical showing that it
    was among the “offenses that have traditionally been triable by
    military commissions,” 10 U.S.C. 950p(a) (2006) (emphasis
    added), might be less problematic. After all, the war on terror is
    unlike recent wars waged among sovereign nations whose troops
    wore identifiable uniforms, and two Presidents have employed
    a modern “enemy combatant” military justice regime. See, e.g.,
    Boumediene v. Bush, 
    553 U.S. 723
    , 733 (2008); Hamdan, 
    548 U.S. at
    570 & n.1. But in codifying “offenses that have
    traditionally been triable by military commissions” in the 2006
    Act, Congress did not encourage or permit any blurring of the
    jurisdictional lines between military commissions and Article III
    courts. The Article III courts were open for prosecuting
    September 11 perpetrators and other members of al Qaeda for
    inchoate conspiracy or other federal crimes. Only years later did
    Congress bar the President from using appropriated funds to
    bring Guantanamo detainees into the United States for any
    purpose. The President has opposed such restrictions on the
    24
    ground that they strip the Executive Branch of “the authority to
    determine when and where to prosecute Guantanamo detainees,
    based on the facts and circumstances of each case and our
    national security interests” — when the Administration wishes
    to employ federal prosecutions [in Article III courts] as “a
    legitimate, effective, and powerful tool in our efforts to protect
    the Nation.” See Statement by the President on H.R. 3304 (Dec.
    26, 2013). So far, Congress has not been persuaded to remove
    the restrictions. In the meantime, the court has a duty “in time
    of war as well as in time of peace, to preserve unimpaired the
    constitutional safeguards of civil liberty.” Quirin, 
    317 U.S. at 19
    . Hewing to the jurisdictional limits for law-of-war military
    commissions, as Supreme Court precedent instructs, preserves
    the separation of powers under which law-of-war military
    commissions are confined to their historical role as necessities,
    not conveniences, of war. Congress’s unequivocal statement of
    its purpose and effect in section 950p of the 2006 Act is
    consistent only with the understanding that it intended to
    maintain the traditional jurisdictional lines.
    II.
    There is still another reason why Bahlul’s conviction for
    inchoate conspiracy (and the other two convictions) must be
    reversed if the 2006 Act is applied retroactively. See Op. at 15.
    Even assuming, contrary to its express statement of the intended
    “effect” of the 2006 Act, 10 U.S.C. § 950p(b), that Congress
    intended the 2006 Act to apply retroactively to create new
    offenses triable by military commissions, Bahlul’s convictions
    must be vacated under the Ex Post Facto Clause of the
    Constitution. U.S. CONST. art. I, § 9, cl. 3.
    A.
    Bahlul’s Ex Post Facto Clause challenge to his convictions
    is properly reviewed de novo for any one of three reasons. In
    25
    applying a plain error standard of review, the majority imposes
    a magic-words requirement nowhere to be found in the precedent
    of the Supreme Court or in the Uniform Code of Military Justice
    as interpreted by the Court of Appeals for the Armed Forces.
    See, e.g., Olano v. United States, 
    507 U.S. 725
     (1993).
    Bahlul unambiguously objected to his trial on the grounds
    he was being charged with offenses that did not exist at the time
    of his alleged conduct. Although he did not refer specifically to
    the Ex Post Facto Clause, his pretrial colloquy with the presiding
    military judge invoked its principles and alerted the military
    commission to the substance of his objection, which is all that is
    required to preserve an objection. See, e.g., United States v.
    Breedlove, 
    204 F.3d 267
    , 270 (D.C. Cir. 2000). The Ex Post
    Facto Clause is designed both “to assure that legislative Acts
    give fair warning of their effect” and to “restrain[] arbitrary and
    potentially vindictive legislation.” Weaver v. Graham, 
    450 U.S. 24
    , 28–29 (1981). Bahlul objected to the judge that after the
    events of September 11, 2001, this country had “put on the side,
    the meaningless American laws, the United Nations, . . . the
    world codes, the international law and what branches out of it
    and the international war laws and the Geneva Conventions and
    the internal American law — military law, and the civil law —
    American civil law” and instead had “legislated new laws and
    this military commission.” Trial Tr. 23. Bahlul repeated that the
    United States had “established a new law in the land, for me and
    for any person that stands in front of you or before you in the war
    in the entire world; but specifically, the Islamic world, and
    specifically also, the Mujahideen Regime.” 
    Id. at 24
    . He
    accused the United States of “getting confused between laws and
    going in an empty circle . . . [b]ecause today, you set a law that
    would impact you tomorrow, and then you will change it, or
    adjust it, or add to it.” 
    Id. at 25
    .
    With these arguments, Bahlul expressly challenged the “new
    26
    laws and this military commission” that was to try him as
    divorced from both international and American law principles
    and as constructed after-the-fact for the purpose of trying
    members of al Qaeda. Bahlul’s objections to “new laws” being
    applied to him and to “chang[ing],” “adjust[ing],” and “add[ing]
    to” existing laws are the considerations animating the ex post
    facto prohibition. The presiding military judge understood
    Bahlul’s arguments and his decision to “boycott” the military
    commission proceedings to be a motion to dismiss for lack of
    jurisdiction, because the law that created the proceedings was
    unlawful or the charges did not state an offense. 
    Id.
     at 98–99.
    Even if Bahlul had forfeited his ex post facto challenge, de
    novo review of a forfeited issue is permitted where the lower
    court has “nevertheless addressed the merits of the issue.”
    Blackmon-Malloy v. Capitol Police Bd., 
    575 F.3d 699
    , 707 (D.C.
    Cir. 2009) (citing United States v. Williams, 
    504 U.S. 36
    , 41
    (1992)); see United States v. Hernandez-Rodriguez, 
    352 F.3d 1325
    , 1328 (10th Cir. 2003); cf. Milhouse v. Levi, 
    548 F.2d 357
    ,
    363 (D.C. Cir. 1976); United States v. Gorski, 
    47 M.J. 370
    , 375
    (C.A.A.F. 1997). This principle applies in both criminal and
    civil cases. See Williams, 
    504 U.S. at 41
    . The Court of Military
    Commission Review considered Bahlul’s constitutional Ex Post
    Facto Clause objection on the merits, 
    820 F. Supp. 2d 1141
    ,
    1218 (C.M.C.R. 2011), and this court may as a matter of
    discretion consider Bahlul’s challenge under a de novo standard
    of review. Given that Bahlul’s objections go to the fundamental
    issue of the military commission’s jurisdiction, this court should
    apply de novo review.
    Furthermore, under the Rules of Military Commissions,
    Bahlul’s challenge to the military tribunal’s jurisdiction and the
    charges against him cannot be waived or forfeited and is
    reviewed de novo. Rule 905(e) provides, in relevant part, that
    failure to raise defenses or objections or to make motions or
    27
    requests “except lack of jurisdiction or failure of a charge to
    allege an offense” at the appropriate time “shall constitute
    waiver.” See THE MANUAL FOR MILITARY COMMISSIONS, at II-
    83–84 (2007). The rule thus defines “waiver” to include
    forfeiture. Similarly, Rule 907(b)(1), “Nonwaivable grounds,”
    states that “[a] charge or specification shall be dismissed at any
    stage of the proceedings if: (A) The military commission lacks
    jurisdiction to try the accused for the offense; or (B) The
    specification fails to state an offense.” 
    Id.
     at II-87. As the
    presiding military judge concluded, Bahlul’s retroactivity
    objection is a claim that the charges against him fail to state an
    offense. Cf. MOORE’S FEDERAL PRACTICE § 612.04 (Lexis 2014)
    (“The defense of failure to charge an offense may be based on
    . . . the unconstitutionality of the statute relied upon.”); see also
    United States v. Haddock, 
    956 F.2d 1534
    , 1542 (10th Cir. 1992),
    abrogated on other grounds by United States v. Wells, 
    519 U.S. 482
     (1997); United States v. Gilbert, 
    813 F.2d 1523
    , 1528–29
    (9th Cir. 1987); United States v. Seuss, 
    474 F.2d 385
    , 387 n.2
    (1st Cir. 1973).
    B.
    The government concedes that the Ex Post Facto Clause
    applies in military commission prosecutions under the 2006 Act
    of detainees at Guantanamo Bay. See Resp’t’s Br. 64. This
    conclusion follows from Boumediene, 
    553 U.S. at
    766–71. Like
    the Suspension Clause at issue there, the Ex Post Facto Clause
    is “one of the few safeguards of liberty specified in a
    Constitution that, at the outset, had no Bill of Rights,” 
    id. at 739
    ,
    and serves both to protect individuals and to preserve the
    Constitution’s separation-of-powers structure. See 
    id.
     at 739–46;
    Landgraf, 
    511 U.S. at
    267–68; Weaver, 
    450 U.S. at
    29 n.10.
    “Because the Constitution’s separation-of-powers structure . . .
    protects persons as well as citizens, foreign nationals who have
    the privilege of litigating in our courts can seek to enforce
    separation-of-powers principles.” Boumediene, 
    553 U.S. at 743
    .
    28
    The Court’s analysis of the extraterritorial reach of the
    Suspension Clause applies to the Ex Post Facto Clause because
    the detainees’ status and location at Guantanamo Bay are the
    same, and the government has pointed to no distinguishing
    “practical obstacles” to its application. See 
    id. at 766
    . The 2006
    Act, in providing that it “does not establish new crimes that did
    not exist before its enactment,” 10 U.S.C. § 950p(a), fairly
    demonstrates Congress’s implied recognition of the reach of the
    fundamental protections embodied in the Ex Post Facto Clause.
    Ex post facto laws are “contrary to the great first principles
    of the social compact,” Calder, 
    3 Dall. at 388
     (opinion of Chase,
    J.), and are “condemned by the universal sentence of civilized
    man” as “oppressive, unjust, and tyrannical,” Ogden v. Saunders,
    
    25 U.S. 213
    , 266 (1827). The Ex Post Facto Clause both
    “ensures that individuals have ‘fair warning’ about the effect of
    criminal statutes,” Landgraf, 
    511 U.S. at
    267–68 (citation
    omitted), and serves as a meaningful structural constraint
    imposed by Article I that goes “to the very root of the power of
    Congress to act all,” Downes v. Bidwell, 
    182 U.S. 244
    , 277
    (1901) (opinion of Brown, J.); see also Weaver, 
    450 U.S. at
    29–30. It “safeguards ‘a fundamental fairness interest . . . in
    having the government abide by the rules of law it establishes to
    govern the circumstances under which it can deprive a person of
    his or her liberty or life.’” Peugh v. United States, 
    133 S. Ct. 2072
    , 2085 (2012) (quoting Carmell v. Texas, 
    529 U.S. 513
    , 533
    (2000)). And it “upholds the separation of powers by confining
    the legislature to penal decisions with prospective effect and the
    judiciary and executive to applications of existing penal law.”
    Weaver, 
    450 U.S. at
    29 n.10.
    Tellingly, when ratified and now, the Ex Post Facto Clause
    addresses the risk that, in response to political pressures, the
    legislature “may be tempted to use retroactive legislation as a
    means of retribution against unpopular groups or individuals.”
    29
    Landgraf, 
    511 U.S. at 266
    ; see Weaver, 
    450 U.S. at 29
    . By
    safeguarding the boundaries between the branches of
    government, the Clause promises that accusations that this
    country has, in Bahlul’s words, “put [our laws] on the side” and
    “established a new law” for our enemies, Trial Tr. 23–24, will
    lack merit. Yet in an odd turn of phase for addressing “one of
    the most basic presumptions of our law,” Johnson, 
    529 U.S. at 701
    , the government urges that the Clause “should apply
    flexibly” here “because of the common law nature of military
    proceedings” and “because Bahlul’s conduct was criminal when
    done,” albeit under statutes providing for prosecution in an
    Article III court. Resp’t’s Br. 62–63, 67. The government’s
    “flexible” approach to the Ex Post Facto Clause, relying on the
    position that Bahlul’s conduct may have been proscribed by laws
    other than those under which he was charged and convicted, “is
    a standardless exercise in crime by analogy,” Pet’r’s Reply Br.
    21, that the Supreme Court has condemned, see, e.g.,
    Papachristou v. Jacksonville, 
    405 U.S. 156
    , 168–69 (1972), and
    the law of war forbids, see, e.g., Rome Statute of the
    International Criminal Court art. 22, July 17, 1998, 2187
    U.N.T.S. 90; 6 LAW REPORTS OF TRIALS OF WAR CRIMINALS at
    95 (practices such as “application of principles of law
    condemned by the practice of civilised nations such as
    punishment by analogy . . . are all properly classed as war
    crimes”).
    C.
    Article I military commissions are an extraordinary tool
    designed to permit the military to infringe on the Article III
    power of the judiciary only to accomplish specific and discrete
    objectives. Through the use of military commissions, the
    government can provide a substitute for civilian courts in
    occupied territories and in places where martial law has been
    declared. See Hamdan, 
    548 U.S. at
    595–96 (plurality op.); see
    
    id. at 683
     (Thomas, J., dissenting). As relevant here, military
    30
    commissions may be convened as an “incident to the conduct of
    war,” to prosecute law-of-war offenses. Quirin, 
    317 U.S. at
    28–29; see Hamdan, 
    548 U.S. at
    596–97 (plurality op.); 10
    U.S.C. § 948b(a) (2006). The retroactive expansion of the
    jurisdiction of Article I law-of-war military commissions to
    include offenses that “have [not] traditionally been triable by
    military commissions,” however, contravenes the structural
    limitations embodied in the Ex Post Facto Clause.
    This appears to be a test case brought by the government to
    establish the jurisdiction of law-of-war military commissions
    over inchoate conspiracy where the government has evidence the
    defendant entered into an agreement to engage in terrorist acts
    against the United States, but no evidence the defendant
    committed an overt act that was a law-of-war offense in
    furtherance of the agreement. This approach may assist the
    Executive Branch in surmounting obstacles to prosecutions in
    Article III courts caused by Congress’s recent restrictions on the
    use of appropriated funds to bring Guantanamo detainees into the
    United States. See, e.g., Statement by the President on H.R.
    3304 (Dec. 26, 2013). But it puts at risk the separation of powers
    and the ex post facto principle by ignoring Congress’s plain
    statement of purpose and effect in the 2006 Act, the
    “traditional[]” jurisdiction of military commissions, and the
    international community’s rejection of inchoate offenses as law-
    of-war offenses.
    Accordingly, the inchoate conspiracy charge of which
    Bahlul was convicted under the 2006 Act does not support the
    jurisdiction of the military commission and this conviction must
    be vacated as well as the two convictions vacated by the court.
    All three convictions must be vacated as violations of the Ex
    Post Facto Clause. It remains for the Administration to decide
    whether to bring other charges against Bahlul before a military
    commission or whether to charge him in an Article III court. To
    31
    the extent that Congress has created an obstacle to bringing
    Bahlul to the United States, Congress can remove it. The
    question whether Congress has impermissibly intruded upon the
    President’s Article II powers is not before the court. In the
    meantime, “[t]he laws and Constitution are designed to survive,
    and remain in force, in extraordinary times. Liberty and security
    can be reconciled; and in our system they are reconciled within
    the framework of the law.” Boumediene, 
    553 U.S. at 798
    . I
    concur in the judgment vacating Bahlul’s convictions for
    material support and solicitation, and I respectfully dissent with
    regard to affirmance of Bahlul’s conviction for inchoate
    conspiracy.
    BROWN, Circuit Judge, concurring in the judgment in
    part and dissenting in part: Over five years ago, Ali Hamza
    Ahmad Suliman al Bahlul was convicted of conspiracy,
    solicitation, and providing material support for terrorism.
    Since that time, the government has been defending the
    conviction, first before the Court of Military Commission
    Review and now before this court. In this appeal, the
    government seeks clarification of the prosecutorial tools it can
    employ in the war on terror. While I concur in the court’s
    judgment affirming Bahlul’s conspiracy conviction and
    vacating the solicitation and material support convictions, I
    cannot agree with the way the court reaches that result. By
    reviewing Bahlul’s claims under a plain error standard, the
    court minimizes the value its opinion might provide to the
    government in future prosecutions. And by remanding
    residual issues to a panel, the court delays resolution of
    Bahlul’s case.
    I would definitively answer the important questions
    raised by Bahlul’s appeal, reviewing his ex post facto
    arguments under a de novo standard. I would also affirm
    Congress’s power under the Define and Punish Clause to
    make certain offenses, including conspiracy, triable by
    military commission. This legal saga has endured long
    enough, and we should take this opportunity to resolve
    important legal questions that have arisen from the war on
    terror.
    I
    The opinion of the court provides insightful legal and
    historical background and, in certain areas, well-reasoned
    analysis. The separate opinions of Judges Henderson and
    Kavanaugh afford additional insight. There is much in those
    opinions with which I wholeheartedly agree. But although I
    concur in the court’s judgment, I would reach its conclusion
    through a slightly different path. In this section, I draw on the
    2
    compelling analysis of my colleagues to explain briefly how I
    would dispose of Bahlul’s challenges. In the following
    sections, which contain the analytical bulk of my concurrence,
    I address three issues that I feel are not adequately covered by
    the other opinions: the applicability of ex post facto
    principles to Bahlul’s convictions, Bahlul’s challenge to
    Congress’s power under the Define and Punish Clause, and
    the court’s decision to remand remaining issues to a panel of
    this court.
    I begin by noting the areas where I agree with my
    colleagues. First, for the reasons expressed by Judge
    Kavanaugh, I would review Bahlul’s Ex Post Facto Clause
    and retroactivity arguments under a de novo standard. See
    Opinion of Judge Kavanaugh (Kavanaugh Op.) 30–34; see
    also Opinion of Judge Rogers Part II.A. Bahlul asked the
    Military Judge presiding over his trial a “legal question” that,
    although not a model of clarity, was sufficient to preserve
    those arguments: “Does the law here start from before,
    during, or after?” Supp. App. 37. Furthermore, Rules 905
    and 907 of the Rules of Military Commissions make
    jurisdictional challenges—including Bahlul’s—not subject to
    forfeiture.
    Second, I agree with the court that the Military
    Commissions Act (MCA) of 2006 unambiguously authorizes
    retroactive prosecution for all the crimes enumerated in that
    statute. See Op. Part III. Both the text of the Act—including
    in particular 10 U.S.C. § 948d(a) (2006) (granting military
    commissions           jurisdiction        over        offenses
    “committed . . . before, on, or after September 11, 2001”)—
    and the context of the judicial–legislative dialogue in which
    the Act was passed require this conclusion.
    3
    Third, like the court, I would accept, for the purposes of
    this case only, the government’s concession that the Ex Post
    Facto Clause provides its protection to aliens detained at
    Guantanamo. See Op. 26–28. However, I doubt the
    correctness of the government’s concession. If our review of
    the question were de novo, I would, like Judge Henderson,
    apply the longstanding precedents of the Supreme Court and
    this court and conclude that the Ex Post Facto Clause does not
    apply to Bahlul or other aliens at Guantanamo. See Opinion
    of Judge Henderson.
    Fourth, I would reject Bahlul’s Ex Post Facto Clause
    challenge as it concerns his conspiracy conviction. As Judge
    Kavanaugh explains, prior to 2006, the “law of war”
    provision of 
    10 U.S.C. § 821
     (Article 21 of the Uniform Code
    of Military Justice) preserved the jurisdiction of military
    commissions to try offenses that (1) were codified in federal
    statutes and explicitly made triable by military commission,
    (2) were recognized by the international law of war, or (3)
    were, according to domestic tradition and practice, triable by
    military commission. See Kavanaugh Op. 7–11; cf. Op. 36–
    40 (holding such a conclusion is not plainly erroneous).
    Furthermore, as the Lincoln conspirators’ cases, Quirin,
    Colepaugh, and the Korean War decisions demonstrate,
    domestic practice traditionally treated conspiracy as an
    offense triable by military commission. See Kavanaugh Op.
    11–16; cf. Op. 40–44 (reaching similar conclusion under a
    plain error standard). Because conspiracy was an offense
    triable by military commission before the 2006 MCA,
    Bahlul’s prosecution for that offense did not violate the Ex
    Post Facto Clause. 1
    1
    In upholding Bahlul’s conspiracy conviction, I would not rely on
    
    18 U.S.C. § 2332
    (b). Indeed, by relying on Olano’s fourth prong,
    the court practically concedes that the existence of the conspiracy
    4
    Fifth, I fully agree with the court’s discussion of material
    support and solicitation and its conclusion that those offenses
    were not historically triable by military commission. See Op.
    Part IV.B–C. Thus, I join the court’s decision to vacate
    Bahlul’s convictions for those offenses.
    II
    As noted above, if not for the government’s concession, I
    would hold that, as an alien detained outside the sovereign
    territory of the United States, Bahlul is not entitled to the
    protections otherwise afforded by the Ex Post Facto Clause.
    However, despite my doubts about the extraterritorial
    applicability of the Clause, I do not doubt that its underlying
    principles apply to detainees at Guantanamo. The legal
    principle nullum crimen sine lege, found in the common law
    and international law, constrains the power of the United
    States to prosecute wherever it may do so. But, even if there
    were not a long history of conspiracy charges being tried by
    military commission, invocation of the ex post facto principle
    alone could not help Bahlul or similarly situated detainees.
    As the International Military Tribunal convened at
    provision in Title 18 would not save Bahlul’s conviction if not for
    the court’s application of a plain error standard. See Op. 32–35. I
    am also reluctant to rely on that provision, however, because of the
    significant procedural differences between criminal prosecutions in
    Article III civilian courts and prosecutions before military
    commissions. The parties have not fully briefed the issue, and I
    would be reluctant without such briefing to hold that a law
    retroactively transferring jurisdiction to try an offense from an
    Article III court to a military commission does not violate the Ex
    Post Facto Clause. Because the court utilizes a plain error standard,
    the court also does not fully embrace this novel and potentially far-
    reaching result.
    5
    Nuremberg in the aftermath of World War II thoughtfully
    observed, “the maxim nullum crimen sine lege is not a
    limitation of sovereignty, but is in general a principle of
    justice.” Judgment of October 1, 1946, 1 INTERNATIONAL
    MILITARY TRIBUNAL, TRIAL OF THE MAJOR WAR CRIMINALS
    (IMT) 171, 219 (1947).
    During the proceedings of the International Military
    Tribunal, the defendants, who were charged with conspiring
    to wage aggressive war, complained that ex post facto
    punishment was abhorrent to the law of all civilized nations
    and that no sovereign power had made aggressive war a
    crime, no statute defined aggressive war, no penalty had been
    fixed for its commission, and no court had been created to try
    and punish offenders at the time the acts were committed.
    Nevertheless, the Tribunal recognized that its expression of
    the international law was “itself a contribution to international
    law” and, in setting up the Tribunal, several nations had done
    together what any nation had a right to do singly. Id. at 218.
    The Tribunal stated that “[t]o assert that it is unjust to punish
    those who in defiance of treaties and assurances have attacked
    neighboring states without warning is obviously untrue, for in
    such circumstances the attacker must know that he is doing
    wrong, and so far from it being unjust to punish him, it would
    be unjust if his wrong were allowed to go unpunished.” Id. at
    219.
    In the case of the terrorist attacks of September 11,
    involving the murder of thousands of civilians, the attackers
    knew the civilized world would condemn their actions.
    Bahlul was fully aware of how the world would view his
    complicity in a moral evil, and “so far from it being unjust to
    punish him, it would be unjust if his wrong were allowed to
    go unpunished.” See id.
    6
    III
    Bahlul argues Congress does not have the power under
    the Define and Punish Clause to make triable by military
    commission those offenses not proscribed by the international
    law of war. The court remands this issue to the panel. But
    the issue was fully briefed and argued before the en banc
    court and, for the reasons explained below, see infra Part IV, I
    think we should take the opportunity to resolve Bahlul’s
    challenge now.
    Judge Kavanaugh would resolve this challenge by
    holding that Congress’s authority to establish military
    commissions derives not only from the Define and Punish
    Clause, but from Congress’s war powers more generally,
    including those originating in the Declare War and Necessary
    and Proper Clauses of Article I, Section 8. See Kavanaugh
    Op. Part II. Judge Kavanaugh notes that the war powers
    clauses do not refer to international law and are not defined or
    constrained by that law.          While I agree with Judge
    Kavanaugh’s broad characterization of Congress’s war
    powers, I find his resolution of Bahlul’s claim incomplete.
    By looking to Congress’s authority under the war powers
    clauses, Judge Kavanaugh leaves unresolved the argument
    that Congress’s power under the Define and Punish Clause is
    strictly constrained by international law. I would resolve
    Bahlul’s challenge to Congress’s Define and Punish Clause
    powers on Define and Punish Clause grounds alone, holding
    that the Clause gives Congress far greater powers than Bahlul
    acknowledges. 2
    2
    Judge Kavanaugh’s reliance on the war powers clauses leaves
    unresolved questions such as whether the government may try
    before a military commission members of a terrorist organization
    with which the United States is not engaged in active hostilities.
    7
    Any discussion of the Define and Punish Clause must
    take proper account of two separate but related points. First,
    in drafting the Clause, the Framers were distinctly aware of
    the undefined and adaptable nature of international law. They
    also recognized the concomitant flexibility inherent in that
    law. And they understood that the United States could, and
    indeed should, make use of that flexibility to advance its own
    national security interests. That is, the Framers intended the
    United States—like other nations—to act in its own self-
    interest, albeit within the flexible constraints of international
    law.      Second, the Framers deliberately placed the
    responsibility and prerogative to interpret and define
    international law with Congress—a political branch—rather
    than with the judiciary. This second point is related to the
    first and to some extent demonstrates its truth: If the Framers
    had intended the country to be strictly constrained by
    narrowly-interpreted international law, it would have made
    more sense to place the power to interpret that law with the
    judiciary—the legal branch expert in such tasks. But, instead,
    the Framers placed the power with Congress, intending that
    Congress would interpret and define international law in a
    more flexible way that serves the country’s self-interest, but
    still remains compatible with international norms. The
    Framers recognized the discretion that must necessarily be
    exercised in defining international law, and entrusted that
    discretion to Congress. The judiciary was given only very
    limited power to review Congress’s choices in defining and
    punishing violations of international law, and must exhibit
    tremendous deference to the legislature’s choices in this area.
    With respect to the two principles described above,
    Congress’s decision to make conspiracy an offense triable by
    military commission provides an excellent example of the
    8
    flexibility inherent in international law and ably demonstrates
    congressional prerogatives.
    A
    1
    The history behind the Define and Punish Clause
    supports an expansive reading of Congress’s power under the
    Clause. Both the drafters of the Constitution and their
    eighteenth-century audience would have had more than a
    passing familiarity with Blackstone and Locke—and, perhaps,
    Vattel, Grotius, and other theorists—whose writings not only
    suggest the law of nations was the special domain of the
    executive and legislative branches, not the judiciary, but also
    tend to emphasize the protean quality of international law.
    See THE FEDERALIST NO. 42, at 260 (James Madison)
    (Clinton Rossiter ed., 1961) (referring to the Define and
    Punish Clause as one of the “class of powers, lodged in the
    general government . . . which regulate the intercourse with
    foreign nations”); BERNARD BAILYN, THE IDEOLOGICAL
    ORIGINS OF THE AMERICAN REVOLUTION 27–31 (1967);
    FORREST MCDONALD, NOVUS ORDO SECLORUM:                     THE
    INTELLECTUAL ORIGINS OF THE CONSTITUTION 7, 60, 80
    (1985).
    The Framers were committed to a national government
    agile enough to avoid foreign entanglements and strong
    enough to deter aggression. In part, it was the country’s
    weakness in the face of decades of depredations by pirates in
    the pay of the despots of the Barbary States that added
    urgency to the constitutional convention. In 1785, when
    emissaries Thomas Jefferson and John Adams sought a
    diplomatic solution to America’s piracy problems, Abd al-
    Rahman, the representative of Tripoli’s pasha, coolly
    9
    reiterated his nearly one-million-dollar ransom demand, and
    replied to their peace overtures in terms that would be familiar
    to contemporary Americans. He told the emissaries: “all
    Nations who should not have acknowledged [the Muslims’]
    authority were sinners, that it was [Islam’s] right and duty to
    make war upon whoever they could find and to make Slaves
    of all they could take as Prisoners, and that every Mussulman
    who should be slain in battle was sure to go to Paradise.”
    MICHAEL B. OREN, POWER, FAITH, AND FANTASY: AMERICA
    IN THE MIDDLE EAST, 1776 TO THE PRESENT 26–27 (2007).
    And the fledgling U.S. Republic continued to be victimized,
    paying as much as a tenth of the national treasury to ransom
    its citizens and its ships until well into the nineteenth century
    when President Jefferson finally had a navy equal to the task
    of freeing some shipping lanes. It is inconceivable that the
    drafters, cognizant of this unhappy history and understandably
    wary of the agendas and motives of European powers, would
    have intended a reference to the law of nations to limit
    America’s ability to defend its sovereignty and its citizens to
    only such actions as some international consortium
    sanctioned.       Cf. NOTES OF DEBATES IN THE FEDERAL
    CONVENTION OF 1787, REPORTED BY JAMES MADISON 637,
    (W. W. Norton & Co. 1987) (debate on the Define and Punish
    Clause); THE FEDERALIST NOS. 16, 66, 68 (Alexander
    Hamilton).
    More importantly, the Framers clearly understood that
    parity among sovereign states is an aspect of power.
    Customary international law is often just another name for
    enlightened self-interest. The philosophical and cultural
    environment in which the Constitution developed was
    permeated by the premise of natural law at the core of the
    Constitution. The drafters saw nothing odd in the idea that
    nation-states could commit wrongs or that wronged states
    could punish bad behavior, provided they were strong enough
    10
    to do so. America is not just the passive subject of the law of
    nations; it is a participant of and contributor to it. No one
    doubts the right of all nations “to resort to forcible means for
    the purpose of repressing any one particular nation who
    openly violates the laws of the society which Nature has
    established between them, or who directly attacks the welfare
    and safety of that society.” EMMERICH DE VATTEL, THE LAW
    OF NATIONS, Preliminaries § 22, at 61 (photo. reprint 2005)
    (1854). Punishment contemplated a spectrum of coercive
    means up to and including war. Thus, Congress’s power to
    punish offenses against the law of nations comprehended a
    power to invoke a range of coercive means to preserve and
    maintain the law of nations. These sentiments are also part of
    the organic law of nations. See J. Andrew Kent, Congress’s
    Under-Appreciated Power to Define and Punish Offenses
    Against the Law of Nations, 85 TEX. L. REV. 843, 927 (2007)
    (“The collective enforcement of the law of nations envisioned
    by Vattel, Grotius, and others included the power to punish
    through warfare pirates, terrorists, and other sub-state violent
    groups.”); see also VATTEL, THE LAW OF NATIONS, supra, bk.
    III § 34, at 407 (“[P]rofessed assassins and incendiaries are
    guilty, not only towards the particular victims of their
    nefarious deeds, but also towards the state, which therefore
    proclaims them public enemies. All nations have a right to
    join in a confederacy for the purpose of punishing and even
    exterminating those savage nations.”).
    Moreover, the law of nations includes not only what is
    mandated, such as compliance with self-executing treaty
    obligations, but also what is permitted. See, e.g., HUGO
    GROTIUS, THE LAW OF WAR AND PEACE, bk. 2, ch. 20, § 40,
    226–27 (Walter J. Black 1949) (1625) (permitting nations to
    wage war not only for wrongs committed against themselves,
    but also for wrongs against nature). As one drafter explained:
    “The law of nature, when applied to states or political
    11
    societies, receives a new name, that of the law of nations.”
    JAMES WILSON, OF THE LAW OF NATIONS, in 1 THE WORKS OF
    JAMES WILSON 148 (Robert Green McCloskey, ed., Harvard
    Univ. Press 1967) (1804).
    Commentaries and treatises attempted to summarize how
    natural rights applied to relations between nations. In fact, the
    full title of Vattel’s work is The Law of Nations Or, Principles
    of the Law of Nature, Applied to the Conduct and Affairs of
    Nations and Sovereigns. Thus, such treatises acknowledged
    the undisputed right of each nation to preserve its national
    existence, to punish the violation of its laws, and to defend its
    polity and protect its property, and condemned unwarranted
    violence, conquest, and lawlessness. Vattel distinguishes the
    Positive law of nations (based on treaties, convention, and
    custom) from the Natural or Necessary law of nations. “As to
    the rights introduced by Treaties or by Custom, there is no
    room to apprehend that any one will confound them with the
    Natural law of nations.” VATTEL, THE LAW OF NATIONS,
    supra, Preliminaries § 27, at 63. To the extent these laws
    originated as precepts of reason derived from the law of
    nature, it makes sense that the law can change in response to
    the exigencies of new species of violence.
    The few early cases interpreting the Define and Punish
    Clause acknowledged the flexibility inherent in international
    norms and deference to the exclusive congressional
    prerogatives the clause prescribes. In United States v. Smith,
    18 U.S. (5 Wheat.) 153 (1820), Justice Story noted offenses
    against the law of nations “cannot, with any accuracy, be said
    to be completely ascertained and defined in any public code
    recognised by the common consent of nations.” Id. at 159.
    He acknowledged that Congress could provide its own
    enumeration of offenses or leave the definition, “without
    inconvenience to the law of nations.” Id. at 158.
    12
    In United States v. Arjona, 
    120 U.S. 479
    , 487–88 (1887),
    Chief Justice Waite held that Congress may punish an
    individual who counterfeits another nation’s money because
    the law of nations generally requires prevention of a wrong
    within one nation’s dominion against a nation with whom it is
    at peace.      Thus, Congress could define and punish
    counterfeiting as a violation of the law of nations even though
    counterfeiting was not a widely recognized offense like
    piracy. And there are other early indications from the
    Supreme Court that no mandate in the Constitution requires
    Congress to follow strictly the law of nations. See, e.g., Ware
    v. Hylton, 3 U.S. (3 Dall.) 199, 224 (1796) (Chase, J.)
    (“Suppose a general right to confiscate British property, is
    admitted to be in Congress, and Congress had confiscated all
    British property within the United States, including private
    debts: would it be permitted to contend in any court of the
    United States, that Congress had no power to confiscate such
    debts, by the modern law of nations? If the right is conceded
    to be in Congress, it necessarily follows, that she is the judge
    of the exercise of the right, as to the extent, mode, and
    manner.”); id. at 266 (Iredell, J.) (noting “[t]he power . . . of
    the Legislature of the Union [is limited] by the Constitution of
    the Union” but acknowledging that when the legislature acts
    within a discretion expressly confided by the Constitution its
    enactments are “in all cases obligatory”).
    As Justice Story observed in Smith, the international
    law’s resistance to facile formulas led the Framers to entrust
    Congress with the “power to define” the laws of nations. 18
    U.S. at 159. The range and fluidity of international law, the
    distinctive needs of each nation-state, and dangers of faction
    to a system that relies on myriad sources establishing a
    consensus of nation-state opinion and practice increased the
    13
    necessity for carving out a zone of deference for Congress’s
    authority.
    The Framers labored to separate law from politics
    because they knew that without that boundary, everything
    would be politics. They (wisely) perceived that law is
    (mostly) clear and categorical while politics—statecraft,
    diplomacy, warfare—is murky, a realm Justice Jackson
    evocatively dubbed the “zone of twilight.” Youngstown Sheet
    & Tube Co. v. Sawyer, 
    343 U.S. 579
    , 637 (1952) (Jackson, J.,
    concurring). The structure of the Constitution echoes this
    rhetorical divide. On the political side, the Define and Punish
    Clause is included in Article I, Section 8, grouped with the
    other enumerated war powers such as declaring war, raising
    armies, maintaining a navy, and issuing letters of marque and
    reprisal. On the legal side, the Ex Post Facto Clause in
    Section 9 is part of a list of prohibitions limiting and defining
    the power of the national government over sovereign states
    and the polity newly subject to national power. The single
    exception to this categorization may be the prohibition on
    suspension of the Writ of Habeas Corpus, and that limitation
    can be overridden when it threatens the defense powers
    authorized by Section 8. Cf. Robert J. Pushaw, Jr., The
    Inherent Powers of Federal Courts and the Structural
    Constitution, 86 IOWA L. REV. 735, 744–47 (2001); Martin H.
    Redish, Federal Common Law, Political Legitimacy, and the
    Interpretive Process: An “Institutionalist” Perspective, 83
    NW. U. L. REV. 761, 765 (1989).
    Thus, both the history and the placement of the clause
    demonstrate the power to define and punish was intended to
    give Congress flexibility in protecting national security, not to
    constrain the country’s ability to act by reference to
    international norms. They also suggest the power is a unique
    14
    legislative power separate from traditional federal court
    jurisdiction.
    2
    More modern authorities demonstrate that international
    law has remained as flexible a concept today as it was in
    1789. Like all common law, the law of war is part of an
    evolving process. As the International Military Tribunal at
    Nuremberg explained:
    [I]nternational law is not the product of an international
    legislature, and . . . international agreements . . . have to
    deal with general principles of law . . . . The law of war
    is to be found not only in treaties, but in the customs and
    practices of states which gradually obtained universal
    recognition, and from the general principles of justice
    applied by jurists and practised by military courts. This
    law is not static, but a continual adaptation follows the
    needs of a changing world.
    1 IMT 221.
    The international law of war is an evolving effort to
    protect civilians from the horrors of total war. Weaponry and
    modes of warfare change; human nature does not. Customary
    understandings about the international law of war are revised
    to account for the impact of bigger armies, more lethal
    weapons, and the speed and scope of belligerents’ response.
    Thus, the Lieber Code drafted during our Civil War gave way
    to the 1868 St. Petersburg Declaration, which stated that “the
    progress of civilization should have the effect of alleviating as
    much as possible the calamities of war.” Declaration
    Renouncing the Use, in Time of War, of Certain Explosive
    Projectiles (St. Petersburg Nov. 29/Dec. 11, 1868). The
    15
    Hague Convention of 1899 included the so-called Martens
    Clause, still applicable today, which declared that except
    where otherwise provided within the specific regulations of
    the Convention, “populations and belligerents remain under
    the protection and empire of the principles of international
    law, as they result from the usages established between
    civilized nations, from the laws of humanity, and the
    requirements of the public conscience.” Convention with
    Respect to the Laws and Customs of War on Land (Hague II),
    pmbl., July 29, 1899. Thus, the international community
    continues to recognize the protean nature of the law of war,
    and recognizes that the law may and should develop to
    address the demands of contemporary warfare.
    What is perhaps an ironic example of the fluid
    development of the international law of war can be seen in
    Hamdan v. Rumsfeld (Hamdan I), 
    548 U.S. 557
     (2006). The
    1907 Hague Convention and the Geneva Conventions which
    followed it in 1929 and 1949 sought to provide a bright line of
    demarcation between combatants who could be harmed and
    noncombatants who could not be targeted. Reciprocity was
    the key to this protective regime. Combatants had to act
    under a fixed command structure, wear insignia that clearly
    identified them as combatants, and refrain from targeting or
    killing civilians. In 1977, the International Committee of the
    Red Cross, egged on by non-aligned nations and those within
    the sway of the former Soviet Union, introduced additional
    protocols that broke away from the reciprocity norms,
    allowing parties engaged in nonconventional warfare to refuse
    to wear distinguishing insignia or carry arms openly until
    immediately before an attack, and allowing non-state actors
    “fighting against colonial domination and alien occupation
    and against racist regimes” to assert lawful authority for their
    efforts. Protocol Additional to the Geneva Conventions of 12
    August 1949, art. 1, 44, June 8, 1977. Leading states,
    16
    including the United States, declined to ratify these protocols,
    fearing they would protect terrorists at the expense of
    civilians and allow insurgents to claim status as prisoners of
    war.
    However, in Hamdan I, Justice Stevens broke apart these
    carefully crafted understandings. He concluded that Salim
    Hamdan was entitled to the protections of Article 3 of the
    Geneva Conventions (Common Article 3) without
    determining either the nature of the conflict or the status of
    the combatant, and without deciding whether extending the
    Conventions’ protections to terrorists, anarchists, or brigands
    violated the expectation of the parties. Even Hamdan I’s fans
    lament its “incomplete and at times cursory analysis of critical
    issues involving the Geneva Conventions’ scope and the
    substantive protections the Conventions provide.” Michael
    W. Lewis, International Myopia: Hamdan’s Shortcut to
    “Victory”, 42 U. RICH. L. REV. 687, 689 (2008). They note
    “a certain clumsiness of application and a dearth of analytical
    rigor.” Fionnuala Ní Aoláin, Hamdan and Common Article 3:
    Did the Supreme Court Get It Right?, 91 MINN. L. REV. 1523,
    1524 (2007).
    As Justice Stevens reconstructed Common Article 3,
    plucking bits and pieces out of other articles to suit his
    narrative, members of organizations that routinely target
    civilians and exploit perfidious circumstances were given the
    ability to argue for protections previously available only to
    combatants who followed the rules. Detainees were quick to
    take advantage of these opportunities. In Al Warafi v.
    Obama, 
    716 F.3d 627
     (D.C. Cir. 2013), a member of the
    Taliban claimed protection as a medic under Article 24 of the
    Geneva Convention despite the fact that he did not have the
    mandatory insignia or identification the Convention requires.
    Indeed, Al Warafi was captured carrying a weapon and had
    17
    previously served in a combat role. In Al-Bihani v. Obama,
    
    590 F.3d 866
    , 871, 874 (D.C. Cir. 2010), a detained member
    of al Qaeda argued he must be considered a civilian and
    released because he did not belong to an official state military
    and had not had the opportunity to commit a direct hostile act
    such as firing a weapon in combat. Thus, belligerents who
    did not play by the rules of international law sought to claim
    the protections of that law. It is true that the purpose of the
    Geneva Conventions is to protect human rights during
    wartime—even the rights of combatants who flout the
    Conventions—but it is hard to “reconcile this purpose with
    the concept that a group which targets civilians may benefit
    from that very behavior, by being afforded all the rights of the
    civilians it targets.” Lewis, International Myopia, supra, at
    714–15.
    In Hamdan I, the plurality seized upon the evolving
    nature of the international law of war to extend the protections
    of that law to nonconventional belligerents. But Bahlul
    argues this court should refuse to allow the government to
    leverage that evolving nature to deter those belligerents—an
    approach that would handcuff the United States to a one-way
    ratchet. Instead, we should recognize that the international
    law of war also adapts in a way that allows states to oppose
    nonconventional combatants and protect themselves from
    terrorists.   Even more importantly, however, we must
    acknowledge that the development of international law is a
    task entrusted by the Framers to the legislative branch. The
    judiciary must give Congress extraordinary deference when it
    acts under its Define and Punish Clause powers.
    B
    Under the approach to the Define and Punish Clause
    outlined above, which gives proper regard to the dual
    18
    principles of flexibility and deference, the conspiracy charge
    against Bahlul should stand.          Even if the offense of
    conspiracy was not recognized under international law in
    2001 by the same labels used by Congress in the 2006
    Military Commissions Act, the substance is similar. Indeed, it
    is to be expected that international law, which was largely
    created by jurists trained in the civil law and which only more
    recently has begun to absorb common law ideas and
    institutions, differs formally from our own common law
    tradition. See Colin B. Picker, International Law’s Mixed
    Heritage: A Common/Civil Law Jurisdiction, 41 VAND. J.
    TRANSNAT’L L. 1083, 1104–06 (2008). But that does not
    mean that when Congress decides to implement international
    law domestically it cannot adapt that law to fit within our
    common law institutions. Such adaptation is appropriate both
    because of the evolving nature of international law and the
    necessities of implementing international law in an
    established domestic legal system.            International law
    recognizes analogues to conspiracy and other inchoate
    offenses.
    In civil law countries, conspiracy is generally treated as a
    mode of liability requiring a completed crime.              Peter
    Margulies, Defining, Punishing, and Membership in the
    Community of Nations: Material Support and Conspiracy
    Charges in Military Commissions, 36 FORDHAM INT’L L.J. 1,
    84 (2013). In the United States and other common law
    countries, however, conspiracy is treated as a separate
    offense, requiring only an agreement and, in some instances,
    an overt act furthering the agreement. Id.; see, e.g., 
    18 U.S.C. § 371
     (conspiracy to defraud the United States). International
    law has adopted something of a hybrid approach, recognizing
    conspiracy as a stand-alone offense for some of the most
    serious war crimes—namely, genocide and waging aggressive
    19
    war—and using conspiracy as a mode of establishing liability
    for all other international law offenses.
    With the exceptions of aggressive war and genocide,
    international law does not recognize inchoate acts as stand-
    alone offenses, but as modes of liability. For instance, the
    Rome Statute recognizes that a person will be criminally
    responsible for a crime if that person “[i]n any . . . way
    contributes to the commission or attempted commission of
    such a crime by a group of persons acting with a common
    purpose.” Rome Statute of the International Criminal Court,
    art. 25, § 3(d) (2002); see also id. § 3(b) (a person shall be
    guilty of an offense if he “[o]rders, solicits or induces the
    commission of such a crime which in fact occurs or is
    attempted.”); id. § 3(c) (a person shall be guilty of an offense
    if he “aids, abets or otherwise assists in its commission or its
    attempted commission, including providing the means for its
    commission.”). The difference between inchoate offenses
    under domestic criminal law and the modes of liability under
    international law is that international law requires that for
    someone to be convicted of conspiracy, solicitation, or
    material support, the substantive offense must have been
    completed or attempted. But in defining the crime of
    conspiracy as an inchoate offense, Congress exercised
    precisely the kind of discretion and flexibility the Define and
    Punish Clause envisions. Congress adapted recognized
    international law to fit the country’s particular needs and legal
    system. 3
    3
    Even under the international law standard requiring a completed
    offense, Bahlul was properly convicted. The conspiracy charge
    alleges Bahlul conspired to commit various substantive offenses,
    including murder of protected persons, attacking civilians and
    civilian objects, murder in violation of the law of war, destruction
    of property in violation of the law of war, terrorism, and providing
    material support for terrorism. App. 120. The charge alleges
    20
    It should be of no consequence that the form or name of
    the charges was different from what might be charged in the
    International Criminal Court or another international war
    tribunal. Whether the prosecutor demonstrates a conspiracy
    to obtain a conviction on a substantive offense, or establishes
    a conspiracy to commit a completed act as a stand-alone
    offense is a matter of form that springs from the differences
    between common law and civil law institutions. In matching
    military commission charges to international law offenses, we
    should adopt a functional approach, looking at the conduct
    involved rather than the label given to that conduct. It would
    be senseless to limit military commissions’ ability to try
    terrorists because the government has not adopted the forms
    and names used by international tribunals. Under a functional
    approach, Bahlul’s conviction for conspiracy is sufficiently
    grounded in international law.
    Furthermore, recent international war crimes tribunals
    have recognized as independent offenses conspiracy to
    commit genocide and conspiracy to wage aggressive war. See
    1 IMT 224–26 (recognizing the crime of conspiracy to wage
    aggressive war but not recognizing conspiracy to commit war
    crimes and crimes against humanity because the latter was not
    Bahlul committed eleven overt acts in furtherance of that
    conspiracy. Among other overt acts, the military commission
    found Bahlul had prepared martyr wills “in preparation for the acts
    of terrorism perpetrated by . . . Muhammed Atta, Ziad al Jarrah and
    others at various locations in the United States on September 11,
    2001” and “researched the economic effect of the September 11,
    2001 attacks on the United States.” App. 122–23. Thus, the
    military commission verdict incorporates the finding that Bahlul’s
    co-conspirators completed international law offenses—namely, the
    terrorist attacks of September 11. See Findings Worksheet, App.
    130, 133.
    21
    defined as a separate crime in the Tribunal’s charter);
    Updated Statute of the International Criminal Tribunal for the
    Former Yugoslavia, art. 4 (2009) (making punishable
    “conspiracy to commit genocide” as well as incitement or
    attempt to commit genocide and complicity in genocide);
    Statute, International Criminal Tribunal for Rwanda, art. 2
    (2010) (same); Convention on the Prevention and Punishment
    of the Crime of Genocide, art. 3 (1948) (same). These
    offenses are the progeny of particular conflicts, created to
    address new and previously unimaginable evils. Yet despite
    the innovative and post hoc nature of these particular
    conspiracy prosecutions, there was little if any protest that
    they violated ex post facto principles—the abhorrent nature of
    the offenses vitiated any such “justice” arguments. Similarly,
    it may be the time has come for international law to recognize
    the offense of conspiracy to commit acts of terrorism.
    Terrorism may be the global security challenge of the 21st
    Century, just like aggressive war was in the early 20th
    Century and genocide was in the half century following
    World War II. Perhaps the United States should be a leader in
    this area—a leader in international law commensurate with its
    status as a military leader in the war on terror—recognizing
    the offense of conspiracy to commit acts of terrorism. These
    are not questions for the judiciary, but rather for the
    legislature to answer. And Congress did so with the MCA,
    broadly construing international law to include the offense of
    conspiracy.
    C
    The Framers and subsequent courts recognized that to
    define the law of nations, Congress required a zone of
    deference. Without a measure of deference, legislative fear of
    second-guessing would hobble Congress’s power under the
    Define and Punish Clause, leaving the nation subject to the
    22
    fate Madison depicted for most previous democratic
    experiments: “short in their lives . . . [and] violent in their
    deaths.” THE FEDERALIST NO. 10, supra, at 76 (James
    Madison). Contemporary international practice exhibits the
    same kind of practical deference to permit individual states to
    assess their own obligations.             The principle of
    complementarity requires international tribunals to accord
    deference to state investigations and recognizes that what is
    mandated still leaves room for what is merely permissive.
    Hamdan I’s plurality had no trouble extending Common
    Article 3 to members of organizations like al Qaeda. As
    noted, by stretching Common Article 3 to meet what it clearly
    perceived as a new exigency, the Court participated in the
    law’s evolution. Thus, courts seem permitted to interpret
    international conventions to allow the humanitarian aspect of
    the law to evolve virtually instantaneously. We cannot, on the
    other side of the equation, deny the political branches the
    ability to respond to novel threats no matter how destructive,
    and leave the nation at the mercy of an international
    consensus and subject to the whims of hostile factions who
    could prevent agreement or promote harmful agendas. See,
    e.g., Protocol Additional to the Geneva Conventions of 12
    August 1949, June 8, 1977. This cannot be the logical import
    of arguing that the law of war is the law of nations. It would
    make the Constitution a suicide pact; and the Define and
    Punish Clause had just the opposite purpose.               For
    international law to form a workable system, states need a
    zone of deference. “Exercising judgment within this zone,
    states could refine approaches that were broadly consistent
    with established norms and also fostered global compliance.”
    Margulies, Defining, Punishing, and Membership in the
    Community of Nations, supra, at 16; cf. New State Ice Co. v.
    Liebmann, 
    285 U.S. 262
    , 386–87 (1932) (Brandeis, J.,
    23
    dissenting) (advocating deference to states, which serve as
    laboratories of democracy).
    Of course, deference does not mean there are no limits.
    We are always subject to the limits which restrain any regime
    premised on natural law and dedicated to the protection of
    natural rights.      This is likely what the international
    community meant with the Martens Clause’s reference to the
    “principles of international law” resulting from “the laws of
    humanity[] and the requirements of the public conscience.”
    Hague II, pmbl., July 29, 1899. But a one-sided rigidity
    imposed on an inherently evolutionary international law does
    not do justice, it thwarts it.
    Congress’s determination that conspiracy is an offense
    against the law of nations constitutes a reasonable
    interpretation of international law and is fully consistent with
    that law. Therefore, the judiciary is bound to uphold
    Congress’s exercise of authority under the Define and Punish
    Clause.
    IV
    Finally, I dissent with regard to the court’s remand of
    residual issues to a panel of this court. Bahlul’s appeal has
    been before this court nearly three years, and the court’s
    decision ensures it will remain here at least another term.
    Bahlul’s jury trial, equal protection, and freedom of speech
    challenges are clearly meritless. I would deny them all
    because Bahlul, as an alien located outside the territorial
    United States, is not entitled to the protections of the
    constitutional provisions he invokes, and, alternatively,
    because his claims lack merit for the reasons stated by Judge
    Kavanaugh. See Kavanaugh Op. Parts III, IV, and V.
    However, to the extent the court was not ready to decide these
    24
    challenges, I would have asked the parties for supplemental
    briefing so we could do so.
    More problematic, however, is that by reviewing Bahlul’s
    retroactivity arguments under the plain error standard, the
    court disposes of this case without providing the government
    clear guidance for prosecuting the remaining detainees at
    Guantanamo. Thus, it may be many years before the
    government receives a definitive answer on whether it can
    charge the September 11 perpetrators with conspiracy, or
    whether Congress has the power to make such an offense
    triable by military commission even prospectively. The
    ability to charge conspiracy is an important prosecutorial tool
    in the war on terror, where it can often be difficult for the
    government to procure evidence directly connecting leaders
    of militant groups with specific terror attacks.
    The United States is engaged in a war on terrorism. As
    the various iterations of Hamdan and this case demonstrate,
    the Executive Branch needs concrete guidance as to how it
    can proceed with its prosecution of the September 11
    conspirators and other detainees. Bahlul was first charged
    before a military commission ten years ago. Today, this court
    again leaves the government without any definitive answers.
    The court does not express respect to the coordinate branches
    of government by further delaying the executive’s
    prosecutorial efforts and thwarting the legislative’s expressed
    preference that detainees be tried by military commission. I
    would resolve now the exceedingly important questions
    presented in this case.
    ***
    For these reasons, I would affirm Bahlul’s conspiracy
    conviction and vacate his material support for terrorism and
    25
    solicitation convictions. I would remand to the Court of
    Military Commission Review for it to address the
    consequences of our decision for Bahlul’s life sentence.
    KAVANAUGH, Circuit Judge, concurring in the judgment
    in part and dissenting in part: Of the seven judges on the en
    banc Court for this case, five judges (all but Judge Henderson
    and Judge Brown) agree in light of Boumediene v. Bush that
    the Ex Post Facto Clause applies at Guantanamo. Indeed, the
    Government concedes as much. Given the Government’s
    concession, all seven judges on the en banc Court (including
    Judge Henderson and Judge Brown) therefore apply the Ex
    Post Facto Clause to analyze the offenses that were charged
    against Bahlul under the Military Commissions Act of 2006.
    In doing so, all seven judges reach the same bottom-line result
    that the Court reached in Hamdan II (here, by virtue of the Ex
    Post Facto Clause; there, by virtue of the 2006 Act as
    informed by the Ex Post Facto Clause):              A military
    commission may not try the offense of material support for
    terrorism for conduct that occurred before enactment of the
    2006 Act.1 All seven judges likewise conclude that a military
    commission may not try the offense of solicitation for conduct
    that occurred before enactment of the 2006 Act. The Court is
    unanimous that those two offenses were not war crimes
    triable by military commission at the time of Bahlul’s conduct
    in 2001. Therefore, all seven judges agree that we must
    vacate Bahlul’s material support for terrorism and solicitation
    convictions as ex post facto violations.
    1
    So that there is no confusion as an historical matter and to be
    clear about the legal implications of the majority opinion, it is
    important to emphasize that the majority opinion’s analysis and
    vacatur of Bahlul’s material support for terrorism conviction
    necessarily mean that Salim Hamdan’s material support for
    terrorism conviction likewise had to be vacated, which is what the
    Hamdan II panel did. In other words, the majority opinion relies on
    a slightly different rationale than did Hamdan II (the Ex Post Facto
    Clause itself rather than the 2006 Act as informed by the Ex Post
    Facto Clause), but the majority opinion reaches the same result:
    The offense of material support for terrorism may not be tried by
    military commission for conduct that occurred before the 2006 Act.
    2
    As to conspiracy, six of the seven judges (all but Judge
    Rogers) uphold Bahlul’s conspiracy conviction against his ex
    post facto objection. Two of us (Judge Brown and I) would
    do so by employing de novo review and concluding that
    conspiracy, unlike material support for terrorism and
    solicitation, has long been an offense triable by military
    commission, including at the time of Bahlul’s conduct in
    2001. The majority opinion likewise upholds Bahlul’s
    conspiracy conviction but does so by employing plain error
    review. The majority opinion believes that Bahlul forfeited
    his ex post facto objection by not raising the objection at trial.
    I write separately to explain my analysis of these difficult
    questions, in particular my analysis of the conspiracy issue.
    On September 11, 2001, Osama bin Laden learned the
    results of al Qaeda’s attack on the United States by listening
    to a radio. That radio was operated by bin Laden’s trusted
    aide, Ali Hamza Ahmad Suliman al Bahlul. A native of
    Yemen, Bahlul had moved to Afghanistan in the late 1990s to
    join al Qaeda. Al Qaeda was and remains an international
    organization whose stated goals are to drive the United States
    from posts in the Middle East, to destroy the State of Israel,
    and to dislodge moderate Islamic regimes and establish
    radical Islamic control over the greater Middle East. To
    advance its broad objectives, al Qaeda employs terrorist
    attacks on civilian and military targets.
    After his arrival in Afghanistan in the late 1990s, Bahlul
    became deeply embedded in al Qaeda’s operations. He
    pledged allegiance to bin Laden. He trained at an al Qaeda
    terrorist camp. He was appointed by bin Laden to lead al
    Qaeda’s media and propaganda operation. Bahlul produced a
    recruitment video glorifying al Qaeda’s October 2000
    bombing of the U.S.S. Cole, an attack that killed 17
    3
    Americans. Bahlul personally arranged the loyalty oath and
    transcribed the “martyr will” of Mohammed Atta, Bahlul’s
    one-time roommate and the hijacker who flew American
    Airlines Flight 11 into the North Tower of the World Trade
    Center on September 11th. Bahlul performed the same
    services for Ziad Jarrah, another of Bahlul’s former
    roommates, who hijacked and piloted United Airlines Flight
    93, the flight that apparently was headed to destroy the U.S.
    Capitol Building or the White House until it was downed in a
    Pennsylvania field by American passengers who fought back.
    Bahlul later said that he himself would have participated on
    September 11th as hijacker number 20, but bin Laden deemed
    his “media man” too essential to lose.
    By the time of the attacks on September 11, 2001, bin
    Laden, Bahlul, and other senior al Qaeda leaders had already
    evacuated from al Qaeda’s headquarters in Kandahar and
    relocated to a remote mountainous region between Kabul and
    Khost. Soon thereafter, Bahlul fled from Afghanistan to
    Pakistan. In late 2001, while in Pakistan, he was captured.
    Since 2002, he has been detained by the U.S. Military at the
    U.S. Naval Base in Guantanamo pursuant to the 2001
    Authorization for Use of Military Force. See Pub. L. No.
    107-40, § 2(a), 
    115 Stat. 224
    , 224. The AUMF remains in
    effect and authorizes the Government to detain enemy
    combatants “for the duration of the relevant conflict” – in this
    instance, the ongoing global war that the United States and its
    allies are engaged in against al Qaeda and its associated
    forces. Hamdi v. Rumsfeld, 
    542 U.S. 507
    , 521 (2004)
    (controlling opinion of O’Connor, J.); see Uthman v. Obama,
    
    637 F.3d 400
    , 402 (D.C. Cir. 2011).2
    2
    The ongoing global war against al Qaeda and its associated
    forces is overlapping but distinct, in law and in fact, from the war in
    Afghanistan against the former Taliban regime and Taliban forces.
    4
    In addition to detaining Bahlul, the U.S. Government also
    exercised its well-established authority to try him before a
    military commission for war crimes. See 10 U.S.C. § 948d
    (2006); 
    10 U.S.C. § 821
     (2000); Hamdan v. Rumsfeld, 
    548 U.S. 557
    , 592-93 (2006); In re Yamashita, 
    327 U.S. 1
    , 7-8
    (1946); Ex parte Quirin, 
    317 U.S. 1
    , 28 (1942). The
    Government ultimately charged Bahlul with three offenses
    specified in the Military Commissions Act of 2006:
    conspiracy to commit war crimes, material support for
    terrorism, and solicitation of war crimes. See Pub. L. No.
    109-366, 
    120 Stat. 2600
    ; 10 U.S.C. §§ 950u, 950v(b)(25),
    950v(b)(28) (2006). Bahlul did not contest the relevant
    factual allegations, but he vehemently objected to the
    legitimacy of the military commission proceeding. The
    military commission convicted Bahlul of all three offenses
    and sentenced him to life in prison. The U.S. Court of
    Military Commission Review affirmed. See United States v.
    Bahlul, 
    820 F. Supp. 2d 1141
     (C.M.C.R. 2011) (en banc).
    Bahlul appealed to this Court, and we granted en banc review.
    Bahlul challenges his military commission convictions on
    five distinct constitutional grounds: (i) the Article I Ex Post
    Facto Clause, (ii) the Article I Define and Punish Clause,
    (iii) the jury trial protections of Article III and the Fifth and
    Sixth Amendments, (iv) the equal protection component of
    the Due Process Clause of the Fifth Amendment, and (v) the
    free speech protections of the First Amendment.
    With respect to his material support for terrorism and
    solicitation convictions, Bahlul’s Ex Post Facto Clause
    The potential end of the U.S. combat mission against Taliban forces
    in Afghanistan obviously does not mean the end of the global war
    against al Qaeda and its associated forces.
    5
    argument is correct because those offenses were not war
    crimes triable by military commission at the time of Bahlul’s
    conduct in 2001. With respect to his conspiracy conviction,
    however, Bahlul’s Ex Post Facto Clause challenge lacks merit
    because conspiracy has long been proscribed under U.S. law
    as a war crime triable by military commission, including at
    the time of Bahlul’s conduct. Bahlul’s other arguments are all
    unavailing. Therefore, I would affirm Bahlul’s conspiracy
    conviction, vacate his material support for terrorism and
    solicitation convictions as ex post facto violations, and
    remand to the U.S. Court of Military Commission Review for
    it to address the consequences, if any, for Bahlul’s life
    sentence.
    I
    Bahlul’s primary argument to this Court rests on the Ex
    Post Facto Clause of Article I, Section 9 of the Constitution.
    See U.S. CONST. art. I, § 9, cl. 3 (“No Bill of Attainder or ex
    post facto Law shall be passed.”). Among other things, the
    Ex Post Facto Clause bars retroactive prosecution of new
    offenses. See Peugh v. United States, 
    133 S. Ct. 2072
    , 2081
    (2013); Collins v. Youngblood, 
    497 U.S. 37
    , 42-43, 52 (1990).
    Bahlul contends that (i) the Ex Post Facto Clause applies to
    military commissions at Guantanamo and (ii) the three
    offenses in the 2006 Act that were charged against him –
    conspiracy to commit war crimes, material support for
    terrorism, and solicitation of war crimes – were new offenses
    that were not triable by military commission at the time of his
    conduct back in 2001.
    In response, the Government concedes (correctly) that the
    Ex Post Facto Clause applies to military commissions at
    Guantanamo. Cf. Boumediene v. Bush, 
    553 U.S. 723
    , 766-71
    6
    (2008).3 And the Government all but concedes (again
    correctly) that material support for terrorism and solicitation
    3
    As a general matter, the U.S. Constitution applies to U.S.
    citizens worldwide and to non-U.S. citizens within the 50 states and
    the District of Columbia, but not to non-U.S. citizens in foreign
    countries. See Zadvydas v. Davis, 
    533 U.S. 678
    , 693 (2001);
    United States v. Verdugo-Urquidez, 
    494 U.S. 259
    , 264-75 (1990);
    
    id. at 275-78
     (Kennedy, J., concurring); Reid v. Covert, 
    354 U.S. 1
    ,
    5-14 (1957) (plurality opinion); Johnson v. Eisentrager, 
    339 U.S. 763
    , 768-85 (1950).
    A more nuanced issue is the reach of the Constitution to non-
    U.S. citizens in an in-between category: in territories owned or
    controlled by the United States, such as Puerto Rico and Guam.
    Determining whether the Constitution applies to non-U.S. citizens
    in U.S. territories requires a “functional” rather than “formalistic”
    analysis of the particular constitutional provision and the particular
    territory at issue. Boumediene v. Bush, 
    553 U.S. 723
    , 762, 764
    (2008). The Court focuses on whether it would be “impracticable
    and anomalous” to extend the constitutional guarantee in question
    to non-U.S. citizens in the territory at issue. 
    Id. at 759
     (quoting
    Reid v. Covert, 
    354 U.S. 1
    , 74 (1957) (Harlan, J., concurring)); see
    Balzac v. Porto Rico, 
    258 U.S. 298
     (1922) (Puerto Rico); Dorr v.
    United States, 
    195 U.S. 138
     (1904) (U.S.-occupied Philippines);
    Hawaii v. Mankichi, 
    190 U.S. 197
     (1903) (pre-statehood Hawaii).
    In Boumediene, the Court determined that Guantanamo was de
    facto U.S. territory – akin to Puerto Rico, for example – and not
    foreign territory. See 
    553 U.S. at 769
     (“In every practical sense
    Guantanamo is not abroad; it is within the constant jurisdiction of
    the United States.”); compare Eisentrager, 
    339 U.S. at 777-81
    (habeas corpus right does not extend to U.S.-controlled military
    prison in post-World War II Germany); Al Maqaleh v. Hagel, 
    738 F.3d 312
    , 317 (D.C. Cir. 2013) (habeas corpus right does not
    extend to U.S. military base in wartime Afghanistan). The Court
    then determined that it would not be “impracticable or anomalous”
    to extend the habeas corpus right to non-U.S. citizen detainees at
    Guantanamo. See Boumediene, 
    553 U.S. at 769-71
    . As the
    Government concedes, the Boumediene analysis leads inexorably to
    7
    were new offenses that were not triable by military
    commission back in 2001. See Hamdan v. United States, 
    696 F.3d 1238
    , 1252 (D.C. Cir. 2012) (Hamdan II). But the
    Government forcefully argues that one of the three offenses
    charged against Bahlul, conspiracy, was not a new offense.
    According to the Government, conspiracy has long been
    triable by military commission under U.S. law, including at
    the time of Bahlul’s conduct.
    The relevant military commission law in effect at the
    time of Bahlul’s conduct was 
    10 U.S.C. § 821
    . That statute
    was first enacted in 1916 and then re-enacted in 1950 as part
    of the Uniform Code of Military Justice. See Pub. L. No. 81-
    506, 
    64 Stat. 107
    , 115 (1950); Pub. L. No. 64-242, 
    39 Stat. 619
    , 653 (1916). As of 2001, at the time of Bahlul’s conduct,
    Section 821 provided as follows:
    The provisions of this chapter conferring jurisdiction
    upon courts-martial do not deprive military commissions,
    provost courts, or other military tribunals of concurrent
    jurisdiction with respect to offenders or offenses that by
    statute or by the law of war may be tried by military
    commissions, provost courts, or other military tribunals.
    
    10 U.S.C. § 821
     (2000) (emphasis added).
    As the Deputy Solicitor General aptly stated at oral
    argument, the question at the heart of this case is whether, as
    of 2001, conspiracy to commit war crimes was an offense
    proscribed under the “law of war” prong of Section 821. See
    the conclusion that the ex post facto right applies at Guantanamo.
    It would be no more impracticable or anomalous to apply the
    Article I, Section 9 ex post facto right at Guantanamo than it is to
    apply the Article I, Section 9 habeas corpus right at Guantanamo.
    8
    Tr. of Oral Arg. at 15-20. The Supreme Court faced that
    exact same question in Hamdan v. Rumsfeld, 
    548 U.S. 557
    (2006). The Court as a whole did not decide the issue
    because it was not necessary to do so given the Court’s
    conclusion that the military commissions then in place were
    unlawful on certain procedural grounds. As a result, there is
    no binding precedent from that case on the conspiracy issue.
    But seven Justices opined on the conspiracy question and split
    4-3 in contrasting opinions written by Justice Stevens and
    Justice Thomas. (Justice Kennedy did not address the
    conspiracy charge. Chief Justice Roberts did not take part in
    the case.)      Justice Stevens’s opinion concluded that
    conspiracy was not a law of war offense under Section 821.
    See 
    548 U.S. at 600-12
    . Justice Thomas’s opinion concluded
    that conspiracy was a law of war offense under Section 821.
    See 
    id. at 697-706
    .
    Importantly for our purposes as a lower court, all seven
    Justices who addressed the Section 821 “law of war” issue in
    Hamdan agreed that it turned on the content of the “common
    law of war” and required careful evaluation of historical U.S.
    military commission precedents involving conspiracy. 
    Id. at 602
     (Stevens, J.); 
    id. at 689
     (Thomas, J.). Although the two
    opinions reached different answers, they considered the same
    basic question: Did the U.S. military commission precedents
    suffice to show that conspiracy was a law of war offense
    triable by military commission under Section 821?
    The detailed historical inquiry undertaken by the seven
    Justices in Hamdan was not idle background discussion. On
    the contrary, the historical inquiry followed from the text of
    Section 821. Enacted in 1916 when Congress amended the
    Articles of War and set forth new rules for courts-martial, and
    then re-enacted in 1950 as part of the Uniform Code of
    Military Justice, Section 821 provided that the new rules
    9
    governing courts-martial did not “deprive” military
    commissions of their pre-existing authority. 
    10 U.S.C. § 821
    (2000).4 Notwithstanding Section 821’s somewhat unusual
    negative phrasing, the Supreme Court has repeatedly
    interpreted Section 821 as affirmative statutory authorization
    for the Executive Branch to convene military commissions to
    try war crimes. See Hamdan, 
    548 U.S. at 592
    ; In re
    Yamashita, 
    327 U.S. 1
    , 7-8 (1946); Ex parte Quirin, 
    317 U.S. 1
    , 28 (1942). With its reference to statutory offenses, Section
    821 authorizes military commissions to try offenses such as
    spying and aiding the enemy that are triable by military
    commission under federal statute. See 
    10 U.S.C. §§ 904
    , 906
    (2000); Quirin, 
    317 U.S. at 41-42
    . With its reference to the
    “law of war,” a term that encompasses the international law of
    war, Section 821 authorizes military commissions to try
    offenses that are war crimes under international law. See
    Yamashita, 
    327 U.S. at 7, 14-16
    . Moreover, as the seven
    Justices in Hamdan recognized with their extensive focus on
    U.S. military commission precedents – and as the Supreme
    Court stated in Madsen v. Kinsella in 1952 and Yamashita in
    1946 – Section 821’s “law of war” prong also expressly
    preserved the authority of military commissions to try
    offenses that had traditionally been tried by U.S. military
    commissions as of 1916 and 1950. See Madsen v. Kinsella,
    
    343 U.S. 341
    , 352 (1952) (statute “states unequivocally that
    Congress has not deprived such commissions or tribunals of
    4
    The precise text of Section 821 and its predecessor statutes
    has varied slightly over time, but the anti-deprivation language has
    been present in every iteration. See Pub. L. No. 64-242, 
    39 Stat. 619
    , 653 (1916) (“shall not be construed as depriving military
    commissions”); Pub. L. No. 66-242; 
    41 Stat. 759
    , 790 (1920)
    (“shall not be construed as depriving military commissions”); Pub.
    L. No. 81-506, 
    64 Stat. 107
    , 115 (1950) (“shall not be construed as
    depriving military commissions”); Pub. L. No. 84-1028, 70A Stat.
    1, 44 (1956) (“do not deprive military commissions”).
    10
    the existing jurisdiction which they had over such offenders
    and offenses as of August 29, 1916”); Yamashita, 
    327 U.S. at 20
     (statute authorized military commissions “to preserve their
    traditional jurisdiction over enemy combatants”); cf. Sekhar v.
    United States, 
    133 S. Ct. 2720
    , 2724 (2013) (when “a word is
    obviously transplanted from another legal source, whether the
    common law or other legislation, it brings the old soil with
    it”) (internal quotation mark omitted).
    Bahlul nevertheless argues that the phrase “law of war”
    in Section 821 encompasses only international law offenses
    and not those offenses traditionally triable by U.S. military
    commissions. In other words, Bahlul says that Section 821,
    although expressly crafted not to “deprive” U.S. military
    commissions of their existing common-law authority over
    conspiracy and other offenses, did in fact deprive military
    commissions of that authority for offenses that were not also
    proscribed by the international law of war.
    Bahlul’s argument that Section 821’s “law of war” prong
    consists exclusively of international law offenses is
    inconsistent with the text and textually stated purpose of
    Section 821, as well as with Supreme Court precedents such
    as Madsen and Yamashita interpreting Section 821. Perhaps
    most tellingly for present purposes, Bahlul’s interpretation of
    Section 821 conflicts with what the Supreme Court actually
    did in Hamdan. Seven Justices in Hamdan analyzed the “law
    of war” embodied in Section 821 as the international law of
    war supplemented by established U.S. military commission
    precedents. Indeed, that is the only interpretation of Section
    821 that squares with how the seven Justices analyzed the
    question in Hamdan.
    In short, at the time of Bahlul’s conduct, Section 821
    authorized military commissions to try offenses drawn from
    11
    three bodies of law: federal statutes defining offenses triable
    by military commission, the international law of war, and
    historical U.S. military commission tradition and practice as
    preserved by Congress when it enacted Section 821 in 1916
    and 1950.5
    At the time of Bahlul’s conduct, neither any federal
    statute nor the international law of war proscribed conspiracy
    as a war crime triable by military commission. So the
    question we must decide is whether U.S. military commission
    precedents treated conspiracy as an offense triable by military
    commission. In other words, we must decide the question that
    was addressed by seven Justices in Hamdan but not decided
    by the Court. The answer, in my view, is yes: U.S. military
    commission precedents have treated conspiracy as an offense
    triable by military commission.
    I base that conclusion in substantial part on the 1865
    military commission conviction of the conspirators who
    5
    A passage in this Court’s decision in Hamdan II – a passage
    beginning “Third,” in the third-to-last paragraph of the opinion –
    suggested that the phrase “law of war” in Section 821 encompassed
    offenses under the international law of war but did not cover other
    offenses that were rooted only in U.S. military commission
    precedents. See Hamdan v. United States, 
    696 F.3d 1238
    , 1252
    (D.C. Cir. 2012) (Hamdan II). That statement was not necessary to
    the result in Hamdan II because, as the opinion explained, material
    support for terrorism was not an offense under the international law
    of war or under U.S. military commission precedents. See 
    id.
     In
    any event, as the Deputy Solicitor General persuasively explained
    at oral argument, see Tr. of Oral Arg. at 15-20, that statement in
    Hamdan II was underinclusive. Given the text and textually stated
    purpose of Section 821, and the relevant Supreme Court precedents,
    the “law of war” prong of Section 821 covers both offenses under
    the international law of war and offenses sufficiently rooted in U.S.
    military commission precedents.
    12
    plotted to assassinate President Lincoln. Put simply, the
    military commission trial of the Lincoln conspirators is the
    highest-profile and most important U.S. military commission
    precedent in American history. President Andrew Johnson,
    after seeking the advice of the Attorney General, decided to
    try the Lincoln conspirators by military commission for
    violating the law of war rather than by criminal trial in
    civilian court. See Military Commissions, 11 Op. Attorney
    Gen. 297 (1865); see also Ex parte Mudd, 
    17 F. Cas. 954
    (S.D. Fla. 1868). The Lincoln conspirators were expressly
    charged with and convicted of conspiracy – in that case,
    conspiracy to violate the law of war by killing the President
    and Commander in Chief of the Union Army, Abraham
    Lincoln. Indeed, conspiracy was the only offense charged
    against them. After an extensive multi-week trial and
    vigorous argument about the facts and the commission’s
    jurisdiction, numerous conspirators were convicted, and
    several of them were sentenced to death and executed.
    In considering the history of U.S. military commissions,
    particularly at the time of Section 821’s original enactment in
    1916 and its re-enactment in 1950, the Lincoln conspirators
    case looms as an especially clear and significant precedent.
    The Lincoln conspirators precedent does not stand alone.
    The second highest-profile and second most important U.S.
    military commission in American history was the military
    commission trial of the Nazi saboteurs who secretly crossed
    into the United States during World War II. Again, the
    defendants were expressly charged with and convicted of
    conspiracy, as well as of another law of war offense. The
    Attorney General of the United States personally prosecuted
    the case before the military commission. President Franklin
    Roosevelt, the Commander in Chief of the Army and Navy,
    reviewed and affirmed all of the convictions. Upon its
    13
    review, the Supreme Court affirmed the saboteurs’
    convictions based on the other law of war offense, making it
    unnecessary to address conspiracy. See Quirin, 
    317 U.S. at 46
    . Like the Lincoln conspiracy precedent, the trial of the
    Nazi saboteurs still stands as a major precedent in which a
    U.S. military commission charged and convicted the
    defendants of conspiracy.
    To summarize so far: As of 1950 when Congress re-
    enacted Section 821 as part of the Uniform Code of Military
    Justice and expressly preserved the traditional authority of
    U.S. military commissions, the two most well-known and
    important U.S. military commissions in American history
    tried and convicted the defendants of conspiracy.
    And there were other significant precedents as well. For
    example, later in World War II, the Government prosecuted
    another set of Nazi saboteurs by military commission for
    conspiracy. In that case, Assistant Attorney General Tom
    Clark produced a formal memorandum concluding – based in
    large part on the precedents involving the Lincoln
    conspirators and the earlier Nazi saboteurs – that conspiracy
    was a law of war offense triable by military commission. See
    Memorandum from Tom C. Clark, Assistant Attorney
    General, to Myron C. Kramer, Judge Advocate General (Mar.
    12, 1945), reprinted in U.S. Supp. App. 133-139. The
    military commission subsequently convicted the defendants of
    conspiracy. President Truman reviewed and affirmed the
    convictions. And after one of those Nazi saboteurs later
    challenged his conviction in court, the Tenth Circuit upheld
    the conviction, including the conspiracy conviction, in an
    opinion by Judge Murrah. See Colepaugh v. Looney, 
    235 F.2d 429
     (10th Cir. 1956).
    14
    To be sure, against those landmark American precedents,
    some international tribunals and conventions subsequent to
    the original enactment of Section 821 have chosen not to
    make conspiracy a war crime triable by military commission.
    Most notably, the International Military Tribunal at
    Nuremberg did not identify conspiracy to commit war crimes
    as an offense triable before that Tribunal. But the Tribunal
    reached that conclusion over the objections of the American
    prosecution team led by Justice Robert Jackson, and the
    Tribunal did so in part because conspiracy was not recognized
    by European law. See Hamdan, 
    548 U.S. at 611
     (Stevens, J.);
    
    id.
     at 702 n.14 (Thomas, J.).
    In any event, what matters for present purposes is that at
    the time of Bahlul’s conduct, no authoritative source of U.S.
    law had ever negated the validity or authority of the U.S.
    military commission convictions of the Lincoln assassins for
    conspiracy or of the Nazi saboteurs for conspiracy. In 1916,
    when it enacted Section 821, as well as in 1950 when it re-
    enacted the statute, Congress was aware of those significant
    precedents. See 
    id.
     at 592 & n.22 (majority opinion)
    (recounting legislative history of 1950 enactment and noting
    Congress’s awareness of Quirin precedent); Madsen, 
    343 U.S. at
    353 & n.20 (recounting legislative history of 1916
    enactment, including discussion of Civil War, Mexican-
    American War, and Spanish-American War precedents); A
    Bill to Unify, Consolidate, Revise, and Codify the Articles of
    War, Hearing on H.R. 2498: Before Subcommittee No. 1 of
    the House Committee on Armed Services, 81st Cong. 962
    (1949) (“A classical example of the military tribunal is the
    trial of the Lincoln conspirators.”) (testimony of Colonel John
    P. Dinsmore); see also Trials by Courts-Martial: Hearing on
    S. 5320 Before the Senate Committee on Military Affairs, 65th
    Cong. 279 (1919) (Judge Advocate General Enoch H.
    Crowder discussing Lincoln conspirators trial). Moreover,
    15
    the leading authority on military commissions at the time of
    both enactments, Colonel William Winthrop’s treatise on
    military law, repeatedly referenced the Lincoln conspirators
    precedent. See WILLIAM WINTHROP, MILITARY LAW AND
    PRECEDENTS 167, 169, 185 n.38, 334 n.40, 834 & n.77, 836
    n.90, 839 n.5 (rev. 2d ed. 1920).
    By stating that Section 821 did not “deprive” military
    commissions of their traditional authority, Congress
    necessarily incorporated the Lincoln assassins precedent for
    conspiracy when it enacted the original version of Section 821
    in 1916, and it incorporated the Lincoln assassins and Nazi
    saboteur precedents for conspiracy when it re-enacted the
    statute in 1950 as part of the Uniform Code of Military
    Justice. After all, it would be rather bizarre to conclude that
    Congress, by enacting a statute that said it did not “deprive”
    military commissions of their traditional authority, in fact
    silently overruled the two most significant and well-known
    military commission precedents in American history. Since
    1950, moreover, Congress has never backed away from its
    express preservation of traditional U.S. military commission
    authority over conspiracy. Indeed, in the 2006 Act, Congress
    reiterated its longstanding intent and belief that conspiracy
    has “traditionally been triable by military commissions.” 10
    U.S.C. § 950p(a) (2006).
    At the time of Bahlul’s conduct, the other two Branches
    likewise had never undermined the validity of the Lincoln
    conspirators and Nazi saboteur precedents. No U.S. court had
    ever cast any doubt on those landmark military commission
    convictions, or on trying conspiracy by military commission.
    And in the Executive Branch, there is a straight line from now
    to then: In deciding that conspiracy is an offense that may be
    tried by military commission, President Barack Obama is the
    same as President George W. Bush is the same as President
    16
    Harry Truman is the same as President Franklin Roosevelt is
    the same as President Andrew Johnson is the same as
    President Abraham Lincoln.
    In light of the clear and consistent historical record in the
    United States as of the time of Bahlul’s conduct in 2001 – in
    all three Branches of the U.S. Government – it is ultimately
    not persuasive to say, as Bahlul does, that conspiracy was a
    brand new U.S. military commission offense created by the
    2006 Act. If we indulge the idea that Bahlul, holed up with
    bin Laden somewhere in the hills of Afghanistan, consulted
    U.S. military commission law on conspiracy back in 2001, he
    would have readily found the two most well-known U.S.
    military commission precedents, the landmark Lincoln
    assassin and Nazi saboteur cases in which the defendants had
    been convicted of conspiracy.
    In sum, conspiracy was triable by military commission
    under the law of war prong of Section 821 at the time of
    Bahlul’s conduct in 2001. The Ex Post Facto Clause
    therefore does not bar the Government’s prosecution of
    Bahlul under the 2006 Act for conspiracy. And for that same
    reason, to the extent that Bahlul argues that the 2006 Act itself
    incorporates ex post facto principles and bars retroactive
    prosecution of new offenses, the 2006 Act likewise does not
    bar the Government’s prosecution of Bahlul for conspiracy.6
    6
    It would be unconstitutional to apply any new offenses in the
    2006 Act to pre-2006 conduct. In light of the canon of
    constitutional avoidance and Congress’s express statement in the
    text of the 2006 Act that the law did “not establish new crimes,” but
    rather merely codified “offenses that have traditionally been triable
    by military commissions,” I read the 2006 Act consistently with the
    Ex Post Facto Clause to authorize retroactive prosecution only of
    offenses that were already prohibited as war crimes triable by
    military commission under U.S. law at the time of the defendant’s
    17
    By contrast, as the Government all but concedes, there is
    no historical U.S. military commission precedent for trying
    the offenses of material support for terrorism and solicitation
    before U.S. military commissions. And those two offenses
    are not international law of war offenses, nor were they triable
    by military commission under any other federal statute at the
    time of Bahlul’s conduct. The Government’s actions between
    the attacks of September 11, 2001, and the enactment of the
    2006 Act underscore that material support for terrorism and
    solicitation have not been thought to be Section 821 “law of
    war” offenses. During that time, the United States charged 10
    al Qaeda defendants before military commissions. The
    United States did not charge any of them with material
    support for terrorism or solicitation, presumably because it
    was widely understood that those two offenses were not
    covered under Section 821. By contrast, the United States
    charged all 10 al Qaeda defendants with conspiracy,
    presumably because the Government believed, based on the
    conduct. 10 U.S.C. § 950p(a) (2006); see Hamdan v. United States,
    
    696 F.3d 1238
    , 1247 (D.C. Cir. 2012) (Hamdan II); cf. Bond v.
    United States, 
    134 S. Ct. 2077
    , 2087-90 (2014); Northwest Austin
    Municipal Utility District Number One v. Holder, 
    557 U.S. 193
    ,
    205 (2009); Blodgett v. Holden, 
    275 U.S. 142
    , 148 (1927) (Holmes,
    J., concurring) (“as between two possible interpretations of a
    statute, by one of which it would be unconstitutional and by the
    other valid, our plain duty is to adopt that which will save the
    Act.”). The majority opinion disagrees that the 2006 Act can be
    read to incorporate ex post facto principles, even in light of the
    constitutional avoidance canon. I do not think the majority opinion
    is correct about that. But that does not matter in this case. Whether
    it is because of the Act as construed in light of the Ex Post Facto
    Clause or because of the Ex Post Facto Clause itself (or both),
    military commissions at Guantanamo may not prosecute any new
    offenses in the 2006 Act for pre-2006 conduct. The key question is
    which offenses in the 2006 Act are new.
    18
    historical precedents, that conspiracy was covered under
    Section 821.
    In short, unlike conspiracy, material support for terrorism
    and solicitation were not covered under Section 821 at the
    time of Bahlul’s conduct in 2001. See Hamdan II, 696 F.3d at
    1252 (concluding that material support for terrorism was not
    covered under Section 821). Bahlul’s convictions for material
    support for terrorism and solicitation therefore must be
    vacated as ex post facto violations.
    II
    In challenging his convictions, Bahlul also advances a far
    more sweeping constitutional argument. He contends that
    Congress lacks constitutional authority to make conspiracy,
    material support for terrorism, or solicitation war crimes
    triable by military commissions, even prospectively, because
    those offenses are not proscribed under the international law
    of war. Bahlul’s argument, in essence, is that the U.S.
    Constitution (as relevant here) incorporates international law
    and thereby interposes international law as a constitutional
    constraint on what crimes Congress may make triable by
    military commission. On its face, that is an extraordinary
    argument that would, as a matter of U.S. constitutional law,
    subordinate the U.S. Congress and the U.S. President to the
    dictates of the international community – a community that at
    any given time could be unsupportive of or even hostile to
    U.S. national security interests as defined by Congress and the
    President. And because conspiracy is not and has not been an
    offense under the international law of war, the argument
    would render the Lincoln conspirators and Nazi saboteur
    convictions for conspiracy illegitimate and unconstitutional. I
    would reject the argument.
    19
    Bahlul spins out the argument in two different ways.
    First, he contends that Congress’s authority to create offenses
    triable by military commission stems exclusively from the
    Article I Define and Punish Clause, which allegedly confines
    military commissions to trying only international law of war
    offenses. I will consider that argument in this Part II of the
    opinion.     Second, Bahlul contends that the jury trial
    protections of Article III and the Fifth and Sixth Amendments
    generally require jury trials, and that the exception to those
    jury trial protections for military commissions applies only to
    international law of war offenses. I will consider that
    argument in Part III below.7
    Bahlul says that Congress may enact offenses triable by
    U.S. military commissions only under Congress’s Article I,
    Section 8 power to “define and punish . . . Offences against
    the Law of Nations.” U.S. CONST. art. I, § 8, cl. 10. Because
    conspiracy is not an offense under international law, Bahlul
    argues that Congress lacked power under Article I, Section 8
    to make the offense triable by military commission.
    The premise of this argument is incorrect. As the
    Supreme Court has repeatedly stated, Congress’s authority to
    establish military commissions to try war crimes does not
    arise exclusively from the Define and Punish Clause. On the
    contrary, as the Supreme Court has explained, Congress also
    has authority to establish military commissions to try war
    7
    For purposes of Bahlul’s jury trial, equal protection, and First
    Amendment arguments, I will assume for the sake of argument that
    those constitutional protections apply to non-U.S.-citizens at
    Guantanamo. See supra note 3; Kiyemba v. Obama, 
    561 F.3d 509
    ,
    518 n.4 (D.C. Cir. 2009) (Kavanaugh, J., concurring) (similarly
    assuming for sake of argument that Due Process Clause applies to
    Guantanamo). Even so, as I will explain, Bahlul’s arguments are
    unavailing.
    20
    crimes under the Declare War and Necessary and Proper
    Clauses of Article I, Section 8. See U.S. CONST. art. I, § 8,
    cls. 11, 18; Hamdan v. Rumsfeld, 
    548 U.S. 557
    , 591-92 &
    n.21 (2006); Madsen v. Kinsella, 
    343 U.S. 341
    , 346 n.9
    (1952); Ex parte Quirin, 
    317 U.S. 1
    , 26-31 (1942); see also
    WILLIAM WINTHROP, MILITARY LAW AND PRECEDENTS 831
    (rev. 2d ed. 1920) (military commission “is simply an
    instrumentality for the more efficient execution of the war
    powers vested in Congress and the power vested in the
    President as Commander-in-chief in war”). And unlike the
    Define and Punish Clause, the Declare War Clause and the
    other Article I war powers clauses do not refer to international
    law and are not defined or constrained by international law.
    In other words, at least as a matter of U.S. constitutional law
    (as distinct from international law), the United States is not
    subject to the whims or dictates of the international
    community when the United States exercises its war powers.
    Therefore, under the text of Article I, international law is not
    a constitutional constraint when Congress proscribes war
    crimes triable by military commission.
    That interpretation also follows from historical practice.
    In accordance with the constitutional text, Congress since the
    earliest days of the Republic has gone beyond international
    law in proscribing war crimes triable by military commission.
    See 10 U.S.C. §§ 950t(26), 950t(27) (2012) (aiding the enemy
    and spying); 
    10 U.S.C. §§ 904
    , 906 (2000) (same); Articles of
    War of 1806, 
    2 Stat. 359
    , 366, 371 (1806) (same). That
    historical practice strongly supports the conclusion that
    international law is not a constitutional constraint when
    Congress proscribes war crimes triable by military
    commission. Cf. NLRB v. Noel Canning, No. 12-1281 (U.S.
    June 26, 2014) (relying on longstanding historical practice to
    interpret Constitution).
    21
    And perhaps most important for us as a lower court is the
    Supreme Court’s decision in Quirin. There, the Court
    rejected various constitutional challenges to military
    commissions. In so doing, the Court emphasized among other
    things that U.S. military commissions have long possessed
    statutory authority to try the offense of spying, which was not
    and has never been an offense under the international law of
    war. See Quirin, 
    317 U.S. at 41-42
    ; see also U.S. Br. 71
    (spying not an international law of war offense); National
    Institute of Military Justice Amicus Br. 18 n.8 (same);
    Hamdan v. United States, 
    696 F.3d 1238
    , 1246 n.6 (D.C. Cir.
    2012) (Hamdan II) (Kavanaugh, J., concurring) (same).
    Quirin’s approval of spying, a non-international-law-of-war
    offense, as an offense triable by military commission
    confirms that Congress has authority under the Constitution to
    make non-international-law-of-war crimes triable by military
    commission.
    In short, the constitutional text, longstanding statutes, and
    Supreme Court precedent all demonstrate that Article I does
    not limit Congress to international law of war offenses when
    it proscribes war crimes triable by military commission.
    III
    Citing the jury trial protections of Article III and the Fifth
    and Sixth Amendments, Bahlul reprises the same basic
    argument that U.S. military commissions may try only
    international law of war offenses. This version of Bahlul’s
    argument begins with the premise that the Constitution
    requires all crimes to be tried by jury. Bahlul recognizes, as
    he must, that the Supreme Court in Quirin nonetheless
    permitted trial by military commission for war crimes. See Ex
    parte Quirin, 
    317 U.S. 1
    , 38-45 (1942); see also Hamdan v.
    Rumsfeld, 
    548 U.S. 557
    , 592-93 (2006). But Bahlul says that
    22
    this exception to the jury trial right extends only to
    international law of war offenses.
    To begin with, there is no textual support for Bahlul’s
    theory. There is no textual reason to think that the exception
    to the jury trial protections for military commissions is
    somehow confined to international law of war offenses. That
    exception, as the Supreme Court has explained, stems from
    the various war powers clauses in Article I and Article II.
    And those war powers clauses are not defined or constrained
    by international law. See Hamdan, 
    548 U.S. at 591-92
    ;
    Quirin, 
    317 U.S. at 25-27
    .
    Moreover, Bahlul’s novel theory contravenes precedent:
    It is inconsistent with the Lincoln conspirators and Nazi
    saboteurs conspiracy convictions, and it cannot be squared
    with Quirin.
    In Quirin, the defendants argued that they had a
    constitutional right to trial by jury and thus could not be tried
    by military commission. At some length, the Court in Quirin
    specifically rejected the defendants’ Article III and Fifth and
    Sixth Amendment jury trial objections to trial by military
    commission. See Quirin, 
    317 U.S. at 38-45
    . The Court
    explained that the Constitution’s jury trial provisions “did not
    enlarge the right to jury trial” beyond the right as it existed at
    common law. 
    Id. at 39
    . Because the common law did not
    preclude military commission trials, “Article III and the Fifth
    and Sixth Amendments cannot be taken to have extended the
    right to demand a jury to trials by military commission.” 
    Id. at 40
    .
    For present purposes, two things are notable about
    Quirin. First, in reaching its conclusion on the jury trial issue,
    the Court relied on the fact that Congress had made spying an
    23
    offense triable by military commission since the earliest days
    of the Republic. The Court said that the early Congress’s
    enactment of the spying statute “must be regarded as a
    contemporary construction” of both Article III and the Fifth
    and Sixth Amendments “as not foreclosing trial by military
    tribunals, without a jury, of offenses against the law of war
    committed by enemies not in or associated with our Armed
    Forces.” 
    Id. at 41
    . “Such a construction,” the Court said, “is
    entitled to the greatest respect.” 
    Id. at 41-42
    . To reiterate, the
    offense of spying on which the Court relied was not and has
    never been an offense under the international law of war. It
    thus makes little sense to read Quirin as barring military
    commission trial of non-international-law-of-war offenses
    when Quirin, in rejecting a jury trial objection to military
    commissions, relied expressly on a longstanding statute
    making a non-international-law-of-war offense triable by
    military commission. Second, nothing about the Court’s
    reasoning in Quirin on this point depended on whether the
    offense tried before a military commission was an
    international law of war offense or, by contrast, was a military
    commission offense recognized only by U.S. law. In other
    words, the Court never stated that military commissions are
    constitutionally permitted only for international law of war
    offenses, which one would have expected the Court to say if
    the Court believed that military commissions are
    constitutionally permitted only for international law of war
    offenses.
    In short, neither Article I nor the jury trial protections of
    Article III and the Fifth and Sixth Amendments limit
    Congress to the international law of war when Congress
    proscribes war crimes triable by military commission. Put
    another way, the United States may be a leader in the
    international community, not just a follower, when Congress
    authorizes war against a terrorist organization or makes
    24
    crimes such as conspiracy war crimes triable by military
    commission. To be sure, it can be quite prudent (and in some
    circumstances required as a matter of international law) for
    Congress and the President to coordinate closely with the
    international community and to pay careful attention to
    international law when authorizing war and enacting war
    crimes triable by military commission. But those policy
    factors, political realities, and international law considerations
    are not constitutional constraints incorporated into the Article
    I war powers clauses or the jury trial guarantees of Article III
    and the Fifth and Sixth Amendments.
    IV
    Bahlul also raises an equal protection challenge under the
    Due Process Clause of the Fifth Amendment. Bahlul argues
    that the Military Commissions Act of 2006 violated equal
    protection principles because it was underinclusive in
    authorizing military commission trials of alien enemy
    combatants but not of U.S. citizen enemy combatants. See 10
    U.S.C. §§ 948b(a), 948c, 948d(a) (2006); Bolling v. Sharpe,
    
    347 U.S. 497
    , 499 (1954) (Fifth Amendment includes equal
    protection component). That argument is meritless.
    The Government correctly points out that many federal
    laws draw distinctions between U.S. citizens and aliens, and
    that the Supreme Court has upheld many such laws. See, e.g.,
    Demore v. Kim, 
    538 U.S. 510
    , 522 (2003); Mathews v. Diaz,
    
    426 U.S. 67
    , 78-80 (1976); see also Bluman v. FEC, 
    800 F. Supp. 2d 281
    , 287 (D.D.C. 2011), affirmed, 
    132 S. Ct. 1087
    (2012). The Supreme Court has explained that any federal
    “policy toward aliens is vitally and intricately interwoven
    with contemporaneous policies in regard to the conduct of
    foreign relations, the war power, and the maintenance of a
    republican form of government” and that such “matters are so
    25
    exclusively entrusted to the political branches of government
    as to be largely immune from judicial inquiry or interference.”
    Mathews, 
    426 U.S. at
    81 n.17 (quoting Harisiades v.
    Shaughnessy, 
    342 U.S. 580
    , 588-89 (1952)). As a result,
    federal laws drawing distinctions between U.S. citizens and
    aliens – particularly in the context of war and national
    security – are generally permissible so long as they are
    rationally related to a legitimate governmental interest. See
    Demore, 
    538 U.S. at 527-28
    ; Mathews, 
    426 U.S. at 83
    ; United
    States v. Ferreira, 
    275 F.3d 1020
    , 1025-26 (11th Cir. 2001);
    United States v. Lue, 
    134 F.3d 79
    , 87 (2d Cir. 1998); Narenji
    v. Civiletti, 
    617 F.2d 745
    , 747 (D.C. Cir. 1979). Here,
    Congress chose to create a distinct system of military
    commissions to try non-U.S. citizens who commit war crimes.
    The Government reasonably explains that “Congress had a
    vital national security interest in establishing a military forum
    in which to bring to justice foreign unlawful belligerents
    whose purpose it is to terrorize innocent U.S. citizens and to
    murder U.S. military personnel.” U.S. Panel Br. 86. Such a
    wartime distinction between alien enemy combatants and U.S.
    citizens easily satisfies rational basis review. Cf. Johnson v.
    Eisentrager, 
    339 U.S. 763
    , 768-77 (1950). Bahlul’s equal
    protection challenge has no merit.
    V
    Bahlul also raises a First Amendment argument, claiming
    that he was unconstitutionally prosecuted for his political
    speech, including his production of the al Qaeda recruitment
    video celebrating the terrorist attack on the U.S.S. Cole. That
    argument, too, lacks any merit.
    As an initial matter, Bahlul was convicted of conspiracy
    based on his conduct. The military commission found that
    Bahlul, among other acts, “traveled to Afghanistan with the
    26
    purpose and intent of joining al Qaeda,” “underwent military-
    type training at an al Qaeda sponsored training camp,” “acted
    as personal secretary and media secretary of Usama bin Laden
    in support of al Qaeda,” arranged for two September 11th
    hijackers to pledge loyalty oaths to bin Laden, and “operated
    and maintained data processing equipment” “for the benefit of
    Usama bin Laden.” App. 122-23.
    Moreover, although non-U.S. citizens arguably may have
    some First Amendment rights at Guantanamo or in other U.S.
    territories for any speech they engage in there, non-U.S.
    citizens have no First Amendment rights abroad in foreign
    countries. The Supreme Court has applied the Constitution to
    aliens in the United States and in U.S. territories, but has not
    extended constitutional rights to aliens in foreign countries.
    See Boumediene v. Bush, 
    553 U.S. 723
    , 768-71 (2008)
    (applying Article I, Section 9 to U.S. Naval base at
    Guantanamo, which was “[i]n every practical sense . . . not
    abroad”); United States v. Verdugo-Urquidez, 
    494 U.S. 259
    (1990) (declining to apply Fourth Amendment to search and
    seizure of alien’s property in Mexico); Johnson v.
    Eisentrager, 
    339 U.S. 763
     (1950) (declining to apply habeas
    corpus right to U.S.-controlled military prison in Germany);
    see also Al Maqaleh v. Hagel, 
    738 F.3d 312
     (D.C. Cir. 2013)
    (declining to apply habeas corpus right to U.S. military base
    in Afghanistan); Al Maqaleh v. Gates, 
    605 F.3d 84
     (D.C. Cir.
    2010) (same). Therefore, Bahlul had no First Amendment
    rights as a non-U.S. citizen in Afghanistan when he led bin
    Laden’s media operation.
    In addition, even if the First Amendment did apply to
    Bahlul’s speech in Afghanistan, the Supreme Court has made
    clear that the First Amendment does not protect speech such
    as Bahlul’s that is “directed to inciting or producing imminent
    lawless action and is likely to incite or produce such action.”
    27
    Virginia v. Black, 
    538 U.S. 343
    , 359 (2003) (quoting
    Brandenburg v. Ohio, 
    395 U.S. 444
    , 447 (1969)); see also
    United States v. Stevens, 
    559 U.S. 460
    , 471 (2010) (First
    Amendment not understood to protect “speech or writing used
    as an integral part of conduct in violation of a valid criminal
    statute”). That is particularly true when the Government
    seeks “to prevent imminent harms in the context of
    international affairs and national security.”        Holder v.
    Humanitarian Law Project, 
    561 U.S. 1
    , 35 (2010); see United
    States v. Rahman, 
    189 F.3d 88
    , 116-18 (2d Cir. 1999). Under
    that traditional test, the speech encompassed within the
    charges against Bahlul – including a terrorist recruitment
    video produced on foreign soil that “was aimed at inciting
    viewers to join al Qaeda, to kill Americans, and to cause
    destruction” – was not protected speech under the First
    Amendment. United States v. Bahlul, 
    820 F. Supp. 2d 1141
    ,
    1249 (C.M.C.R. 2011) (en banc). The Constitution is not a
    suicide pact. Cf. Terminiello v. City of Chicago, 
    337 U.S. 1
    ,
    37 (1949) (Jackson, J., dissenting).
    VI
    A few words in response to the majority opinion: I find
    the majority opinion surprising both in what it decides and in
    what it declines to decide.
    First, I am surprised by what the majority opinion
    decides. After all, the majority opinion reaches the same
    bottom-line conclusion that this Court reached in Hamdan II:
    The offense of material support for terrorism may not be tried
    by military commission for conduct that occurred before the
    2006 Act. But the majority opinion does so based on the Ex
    Post Facto Clause alone and “overrules” Hamdan II’s
    statement that the 2006 Act itself incorporates ex post facto
    principles. That seems to be a meaningless exercise by the
    28
    majority opinion. Applying the canon of constitutional
    avoidance, Hamdan II reasoned that the 2006 Act could not
    be applied to new offenses that were not previously triable by
    military commission.        Hamdan II was based on its
    understanding of the limits of the Ex Post Facto Clause.
    Hamdan II indicated that the 2006 Act allowed prosecutions
    of the listed offenses for pre-2006 conduct to the extent that
    the Ex Post Facto Clause allowed such prosecutions. As the
    Court said, “Congress incorporated ex post facto principles
    into the terms of” the Act. Hamdan II, 696 F.3d at 1248
    (internal quotation mark omitted). So whether we apply the
    Constitution to inform interpretation of the statute or we apply
    the Constitution to limit the statute, the question in this case is
    the same: What are the constraints imposed by the Ex Post
    Facto Clause?8
    On that question, my view is that the Ex Post Facto
    Clause bars retroactive prosecution at Guantanamo of new
    offenses that were not previously triable by military
    commission. But the majority opinion suggests (although it
    does not definitively conclude) that the Ex Post Facto Clause
    is less of a constraint on the Government and may allow
    8
    Judge Henderson’s concurrence, which speaks only for her,
    notes quite correctly that the majority opinion today overrules
    Hamdan II’s reliance on the 2006 Act (as opposed to the Ex Post
    Facto Clause) as a basis for concluding that material support for
    terrorism may not be tried by military commission for conduct that
    occurred before the 2006 Act. What Judge Henderson does not say
    in her concurrence is this indisputable fact: Based on the Ex Post
    Facto Clause, the majority opinion today reaches the same result as
    Hamdan II by concluding that material support for terrorism may
    not be tried by military commission for conduct that occurred
    before the 2006 Act, which in turn means that Salim Hamdan’s
    material support for terrorism conviction was properly overturned
    by this Court in Hamdan II.
    29
    military commissions at Guantanamo to retroactively
    prosecute offenses that were previously triable as federal
    crimes in Article III federal courts, even if those offenses were
    not previously triable by military commission.
    I am surprised by this rather aggressive suggestion about
    the meaning of the Ex Post Facto Clause. After all, that
    position was not forcefully advocated by the Government in
    its submission to the en banc Court, as the argument appeared
    only in a short discussion late in its brief. In the hour-long
    oral argument, moreover, the Government did not advance
    that argument, and no Judge asked any question along those
    lines or suggested this as a possible approach.
    Moreover, like Judge Brown (as well as Judge Rogers), I
    too respectfully have serious doubts about the majority
    opinion’s suggestion that the Ex Post Facto Clause may allow
    military commissions to retroactively prosecute crimes that
    were previously triable as federal crimes in federal court even
    when they were not previously triable by military
    commission. Can Congress, consistent with the Ex Post Facto
    Clause, really just pull out the federal criminal code and make
    offenses retroactively triable before military commissions? I
    am aware of no commentator who has taken that position or
    even analyzed the question. I have found no precedent taking
    that position or analyzing the question. And even Congress,
    hardly in a passive mode when it enacted the 2006 Act, did
    not go so far as the majority opinion about the meaning of the
    Ex Post Facto Clause. The text of the 2006 Act reveals that
    Congress thought there was no ex post facto problem because
    the listed offenses were previously triable by military
    commission. See 10 U.S.C. § 950p(a) (2006). If Congress
    had thought it enough that there were some prior federal
    criminal statutes on the books, Congress no doubt would have
    relied on that point to respond to the ex post facto concerns.
    30
    But as best as I can tell, no Member said as much. On the
    contrary, the text of the Act itself demonstrates that Congress
    thought it necessary, in order to overcome ex post facto
    objections, to show that the offenses had been previously
    triable by military commission.
    It is especially surprising for the majority opinion to take
    its doubly aggressive approach – overruling one aspect of a
    precedent of this Court and advancing a heretofore unheard-of
    view of the Ex Post Facto Clause’s application to military
    commissions – when it is unnecessary to do so here. After all,
    in what it terms an “independent and alternative” holding, the
    majority opinion says that plain error review applies and
    concludes that the conspiracy conviction was not plain error
    because conspiracy at least arguably was triable by military
    commission under Section 821 at the time of Bahlul’s
    conduct. The majority opinion notes, correctly, that it is
    impossible to describe the Government’s position on
    conspiracy and Section 821 as plain error when the issue
    remains open in the Supreme Court and three Justices in
    Hamdan agreed with the Government’s position. The
    majority opinion could have said no more than what it says
    about Section 821 to resolve the conspiracy ex post facto
    issue for purposes of Bahlul’s appeal.
    Second, from the other direction, I am also surprised by
    what the majority opinion does not decide. We took this case
    en banc specifically to decide whether, consistent with the Ex
    Post Facto Clause, a military commission could try
    conspiracy for conduct that occurred before the 2006 Act.
    Yet the majority opinion does not actually decide that
    question.
    That is because the majority opinion applies the plain
    error standard of review. The majority opinion thus does not
    31
    decide whether there was error in the conspiracy conviction;
    instead, it decides only whether any alleged error was plain.
    Like Judge Brown (as well as Judge Rogers), I too
    disagree with the majority opinion’s use of a plain error
    standard of review. To begin with, Bahlul did not forfeit his
    ex post facto objection, so he is legally entitled to de novo
    review of that issue and does not have to meet the high bar of
    showing plain error. Bahlul raised an ex post facto issue
    when he pled not guilty and, among other things, posed to the
    Military Judge a “legal question”: “Does the law here start
    from before, during, or after?” Supp. App. 37; see id. (Bahlul
    asking whether “the law here” “stems from the action, before
    action, or post action?”).
    But put that aside. Even if Bahlul did not expressly raise
    an ex post facto objection at trial, the issue is not forfeitable
    under Rules 905 and 907 of the Rules of Military
    Commissions. Those Rules contain two exceptions to the
    usual forfeiture rules for objections based on a “lack of
    jurisdiction” or “failure of a charge to allege an offense.”
    MANUAL FOR MILITARY COMMISSIONS pt. II, at II-83-84
    (2007); see id. at II-87; see also MANUAL FOR MILITARY
    COMMISSIONS pt. II, at II-89-91, II-95 (2012). In this case,
    each of those two exceptions applies. As the relevant statutes
    say on their face, the question of whether conspiracy may be
    charged is jurisdictional – whether the military commission
    had “jurisdiction” over the offense. 10 U.S.C. § 948d(a)
    (2006) (military commissions have “jurisdiction to try any
    offense made punishable by this chapter or the law of war”)
    (emphasis added); 
    10 U.S.C. § 821
     (2000) (“provisions of this
    chapter conferring jurisdiction upon courts-martial do not
    deprive military commissions . . . of concurrent jurisdiction
    with respect to offenders or offenses that by statute or by the
    law of war may be tried by military commissions”) (emphases
    32
    added). Indeed, the Military Judge construed Bahlul’s
    sometimes rambling comments as an objection to the military
    commission’s jurisdiction. See Supp. App. at 31-32.
    And in any event, the question raised by Bahlul in this
    Court is surely whether the conspiracy charge fails to “allege
    an offense,” which is the other kind of non-forfeitable
    objection under Rules 905 and 907.9 Although there is
    obviously scarce precedent interpreting the recently
    promulgated Rules of Military Commissions with respect to a
    charge that fails to state an offense, the same basic language is
    found in Federal Rule of Criminal Procedure 12(b)(3)(B).
    That Criminal Rule provides an exception to waiver or
    forfeiture in criminal cases for, among other things, a claim
    that the indictment or information “fails to state an offense.”
    Interpreting that language, courts have determined that
    constitutional objections such as Ex Post Facto Clause claims
    challenging the validity of the charge are objections that the
    charge failed to state an offense – and thus may be raised for
    the first time on appeal and reviewed de novo even if those
    objections were not timely raised in the district court
    proceedings. See United States v. Haddock, 
    956 F.2d 1534
    ,
    1542 (10th Cir. 1992) (reviewing de novo Ex Post Facto
    Clause challenge that was not raised prior to trial); United
    States v. Gilbert, 
    813 F.2d 1523
    , 1528-29 (9th Cir. 1987)
    (constitutional challenges attacking “the sufficiency of the
    information to charge an offense . . . may be raised for the
    9
    Rules 905 and 907 are entitled “waiver” but those Rules, like
    the other Rules of Military Commissions, use that term
    (imprecisely) to cover both waived arguments and forfeited
    arguments. See MANUAL FOR MILITARY COMMISSIONS pt. II, at II-
    83-84, II-87 (2007); MANUAL FOR MILITARY COMMISSIONS pt. II,
    at II-89-91, II-95 (2012); see also Rules 920(f), 1005(f), 1106(e)(6),
    MANUAL FOR MILITARY COMMISSIONS pt. II, at II-115, II-125, II-
    145 (2007).
    33
    first time on appeal”); United States v. Seuss, 
    474 F.2d 385
    ,
    387 n.2 (1st Cir. 1973) (“The defense of failure of an
    indictment to charge an offense includes the claim that the
    statute apparently creating the offense is unconstitutional.
    That objection may be raised for the first time on appeal.”);
    see also United States v. Al Hedaithy, 
    392 F.3d 580
    , 586 (3d
    Cir. 2004) (reviewing de novo Rule 12(b)(3)(B) objection that
    was not raised at trial); United States v. Panarella, 
    277 F.3d 678
    , 682-86 (3d Cir. 2002) (same); United States v. Maybee,
    No. 11-30006, 
    2011 WL 2784446
    , at *3 (W.D. Ark. July 15,
    2011) (“Courts have held that a claim that the indictment fails
    to ‘charge an offense’ includes a claim that the statute
    creating the offense is unconstitutional.”), aff’d, 
    687 F.3d 1026
     (8th Cir. 2012); United States v. Thomas, 
    534 F. Supp. 2d 912
    , 915 (N.D. Iowa 2008) (“It is settled that a claim that
    the indictment fails to state an offense under Rule 12(b)(3)(B)
    includes a claim that the statute creating the offense is
    unconstitutional.”) (internal quotation marks and ellipses
    omitted), aff’d sub nom. United States v. Howell, 
    552 F.3d 709
     (8th Cir. 2009); MOORE’S FEDERAL PRACTICE § 612.04
    (Lexis 2014) (“The defense of failure to charge an offense
    may be based on the absence of an essential element in the
    indictment, indefiniteness of allegations, the lack of a statute
    creating the crime, or the unconstitutionality of the statute
    relied upon.”).10
    10
    Notably, the Advisory Committee on the Federal Rules of
    Criminal Procedure has recently recommended changing this aspect
    of Rule 12(b)(3)(B), apparently because it is somewhat too lenient.
    Under the proposed change, the argument that a charge failed to
    state an offense would no longer be an exception to the usual rules
    governing waiver and forfeiture. In other words, a defendant would
    no longer be able to raise an argument that the charge failed to state
    an offense for the first time on appeal and still receive de novo
    review of that claim. See SUMMARY OF THE REPORT OF THE
    JUDICIAL CONFERENCE COMMITTEE ON RULES OF PRACTICE AND
    34
    Finally, even if the issue had been forfeited and plain
    error review applied, the majority opinion still would possess
    discretion to decide the ex post facto issue under the first
    prong of the plain error test as defined by the Supreme Court
    and conclude that there was no “error” in the conspiracy
    conviction. See United States v. Olano, 
    507 U.S. 725
    , 732
    (1993). The majority opinion should do so. Courts have an
    appropriate role in times of war to decide certain justiciable
    disputes – but we should do so “with as much clarity and
    expedition as possible.” Kiyemba v. Obama, 
    561 F.3d 509
    ,
    522 (D.C. Cir. 2009) (Kavanaugh, J., concurring). The
    majority opinion’s failure to decide the ex post facto question
    with respect to conspiracy does not comport with that
    principle, in my respectful view. Given the various pending
    cases raising the same question and the need for guidance in
    those wartime tribunals, I believe that the majority opinion
    should decide the issue.
    On top of not deciding how the ex post facto principle
    applies to conspiracy trials before military commissions, the
    majority opinion also does not decide Bahlul’s Article I, jury
    trial, equal protection, or First Amendment challenges, but
    rather sends those four issues back to a three-judge panel for
    resolution. I also respectfully disagree with that approach.
    The remaining issues are not that complicated; we have the
    PROCEDURE, Rules Appendix C-15-C-26 (Sept. 2013). But that
    proposed rule change, which has not yet taken effect, just highlights
    what the “fails to state an offense” language means now in the
    Criminal Rules. And that is the same language that the Rules of
    Military Commissions uses. Unless and until the Rules of Military
    Commissions are likewise changed, therefore, an argument that a
    military commission charge failed to state an offense – such as the
    Ex Post Facto Clause argument here – may be raised for the first
    time on appeal and receive de novo review.
    35
    requisite briefing; and we could request supplemental briefing
    if need be. Moreover, those issues are especially easy to
    decide on plain error review, which after all is the standard of
    review that the majority opinion indicates must be applied to
    those issues. Sending the case back to a three-judge panel
    will delay final resolution of this case, likely until some point
    in 2015, given the time it will take for a decision by the three-
    judge panel and then resolution of any future petitions for
    panel rehearing or rehearing en banc. Like Judge Brown, I
    believe that we should resolve the case now, not send it back
    to the three-judge panel.
    In short, I respectfully disagree with the majority
    opinion’s addressing the ex post facto issue in a way that does
    not actually decide the legal issue with respect to conspiracy
    and provides little clarity or guidance on that issue going
    forward, and also with its sending the other four issues back
    to a three-judge panel. There is a time to avoid and a time to
    decide. Now is the time to decide.
    ***
    In sum, I would affirm Bahlul’s conspiracy conviction,
    vacate the material support for terrorism and solicitation
    convictions as ex post facto violations, and remand to the U.S.
    Court of Military Commission Review for it to address the
    consequences, if any, for Bahlul’s life sentence.11
    11
    The Supreme Court in Quirin affirmed the Nazi saboteurs’
    convictions and sentences on one charge and declined to review
    their convictions on the remaining charges. See Ex parte Quirin,
    
    317 U.S. 1
    , 46 (1942). That approach reflected the practice at the
    time for American appellate review of criminal convictions. The
    modern American appellate practice, however, is to address each
    conviction separately in these circumstances. See Rutledge v.
    United States, 
    517 U.S. 292
    , 301-03 (1996); Ray v. United States,
    36
    
    481 U.S. 736
    , 736-37 (1987). Absent contrary indication, I assume
    that Congress intended appellate review under the Military
    Commissions Acts of 2006 and 2009 to proceed in the same
    manner as modern appellate review of multiple criminal
    convictions. For that reason and because a sentence was not
    specified for each individual offense in this case, I have addressed
    the material support for terrorism and solicitation offenses as well
    as the conspiracy offense.
    

Document Info

Docket Number: 11-1324

Citation Numbers: 412 U.S. App. D.C. 372, 767 F.3d 1, 2014 WL 3437485, 2014 U.S. App. LEXIS 13287

Judges: Garland, Henderson, Rogers, Tatel, Brown, Griffith, Kavanaugh

Filed Date: 7/14/2014

Precedential Status: Precedential

Modified Date: 10/19/2024

Authorities (141)

Stern v. Marshall , 131 S. Ct. 2594 ( 2011 )

Ashwander v. Tennessee Valley Authority , 56 S. Ct. 466 ( 1936 )

United States v. Jean Carlo Ferreira , 275 F.3d 1020 ( 2001 )

Pinkerton v. United States , 66 S. Ct. 1180 ( 1946 )

United States v. Williams , 71 S. Ct. 595 ( 1951 )

United States v. Webb, Dennis L. , 255 F.3d 890 ( 2001 )

United States v. Keith Dwayne Gilbert , 813 F.2d 1523 ( 1987 )

People's Mojahedin Organization of Iran v. United States ... , 182 F.3d 17 ( 1999 )

United States v. Thomas , 534 F. Supp. 2d 912 ( 2008 )

Bluman v. Federal Election Commission , 800 F. Supp. 2d 281 ( 2011 )

United States v. Al Bahlul , 820 F. Supp. 2d 1141 ( 2011 )

Bond v. United States , 134 S. Ct. 2077 ( 2014 )

Clark v. Martinez , 125 S. Ct. 716 ( 2005 )

Puckett v. United States , 129 S. Ct. 1423 ( 2009 )

Holder v. Humanitarian Law Project , 130 S. Ct. 2705 ( 2010 )

In Re Yamashita , 66 S. Ct. 340 ( 1946 )

Johnson v. Eisentrager , 70 S. Ct. 936 ( 1950 )

Kwong Hai Chew v. Colding , 73 S. Ct. 472 ( 1953 )

United States v. Public Utilities Commission , 73 S. Ct. 706 ( 1953 )

Cook v. United States , 11 S. Ct. 268 ( 1891 )

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