After the September 11, 2001 terrorist attacks, the Bush Administration began using military commissions rather than Article III courts to try alleged terrorists1 at Guantánamo Bay, Cuba. In response to the Supreme Court’s determination in Hamdan v. Rumsfeld2 (Hamdan I) that these military commissions lacked statutory authorization and were thus invalid, Congress explicitly authorized prosecution by military commission for certain enumerated crimes in the Military Commissions Act of 20063 (MCA). In Hamdan v. United States4 (Hamdan II), the D.C. Circuit held that the MCA did not authorize “retroactive prosecution for conduct committed before [its] enactment . . . unless the conduct was already prohibited under existing U.S. law as a war crime triable by military commission,”5 fearing that a contrary construction would raise constitutional concerns under the Ex Post Facto Clause.6 Recently, in Al Bahlul v. United States,7 the en banc D.C. Circuit overruled Hamdan II’s statutory analysis and instead considered the constitutional question directly, holding that retroactive prosecution for inchoate conspiracy to commit war crimes8 under the MCA did not plainly violate the Ex Post Facto Clause.9 The court found that even before enactment of the MCA, inchoate conspiracy may have been triable by military commission under 10 U.S.C. § 821, which granted military commissions jurisdiction over offenses that “by statute or the law of war may be tried by military commissions.”10 To reach its holding, the court found that, though inchoate conspiracy was not a crime under the international law of war at the time of the defendant’s alleged conduct, it nevertheless may have been a crime under the U.S. common law of war11 — even though the Hamdan II court had found that § 821’s “law of war” did not encompass this category.12 Interpreting § 821’s “law of war” to include the common law of war would misread congressional intent and historical precedents that sought to avoid the risks such a reading would pose for the stability of the international law of war.
Ali Hamza Ahmad Suliman al Bahlul (Bahlul), a native of Yemen, joined al Qaeda in Afghanistan in the late 1990s.13 After Bahlul produced a popular propaganda video celebrating the al Qaeda attack on the U.S.S. Cole and calling for jihad against the United States,14 Osama bin Laden appointed Bahlul as his personal assistant and secretary for public relations — roles in which Bahlul soon became indispensable.15 After the September 11 attacks, Bahlul was captured in Pakistan, turned over to U.S. forces in December 2001, and transferred to the U.S. Naval Base at Guantánamo Bay in 2002.16 In 2004, after President Bush declared Bahlul eligible for trial by military commission, military prosecutors charged him with conspiracy to commit war crimes.17 Soon thereafter, the Hamdan I Court invalidated the existing military commission procedures,18 and Congress enacted the MCA to remedy the procedural flaws.19 The MCA also enumerated thirty war crimes triable by military commission and conferred such jurisdiction for any of those offenses committed “before, on, or after September 11, 2001.”20 In 2008, military prosecutors amended Bahlul’s charges to include three of the MCA’s enumerated offenses: conspiracy to commit war crimes, providing material support for terrorism, and solicitation of others to commit war crimes.21
In his military commission trial, Bahlul mounted no defense;22 the military commission convicted him of all three offenses.23 The Court of Military Commissions Review affirmed Bahlul’s convictions.24 He then appealed to the D.C. Circuit, challenging his convictions as, inter alia, violations of the Ex Post Facto Clause.25 After the D.C. Circuit held in Hamdan II that the MCA did not authorize retroactive prosecution for conduct that was not triable by military commission as a crime under the international law of war at the time the conduct occurred,26 a panel of the D.C. Circuit vacated Bahlul’s convictions.27 While the government had conceded that the Hamdan II reasoning would necessitate that Bahlul’s convictions be vacated, it contested the soundness of that reasoning and petitioned the court for en banc review.28 The D.C. Circuit granted the government’s petition for rehearing en banc.29
The D.C. Circuit affirmed the military commission’s conviction for conspiracy, but vacated and remanded Bahlul’s convictions for material support and solicitation. Writing for the en banc court, Judge Henderson30 first concluded that because Bahlul did not challenge his trial on Ex Post Facto Clause grounds before the military commission, he forfeited this ground for appeal, and the defense needed to show “plain error” to prevail.31 The Court then explicitly overruled Hamdan II’s statutory holding, finding that, because the plain text was clear32 and the legislative intent was “overwhelmingly in favor of retroactive application,”33 the MCA did authorize retroactive prosecution for certain enumerated crimes when committed before, on, or after September 11, 2001.34 Then, the Court addressed Bahlul’s Ex Post Facto Clause challenges to this retroactive prosecution.35
The court determined that Bahlul’s conviction for conspiracy did not plainly violate the Ex Post Facto Clause for “two independent and alternative reasons.”36 First, the court reasoned that the alleged conspiracy was already a federal crime under 18 U.S.C. § 2332(b) when committed.37 By the court’s logic, the MCA’s transfer of jurisdiction to try such conspiracies from Article III courts to military commissions “does not implicate ex post facto concerns”38 because it does not alter “the definition of the crime, the defenses or the punishment.”39
Second, even if a mere shift in jurisdiction were sufficient to offend the Ex Post Facto Clause, the court reasoned that when Bahlul committed his offense, conspiracy may have been a “law of war” offense already triable by military commission under 10 U.S.C. § 821.40 The court acknowledged the government’s concession that conspiracy was not a crime under the international law of war.41 However, while the D.C. Circuit in Hamdan II concluded that § 821’s reference to the “law of war” means only the international law of war,42 here the court entertained the government’s argument43 that § 821’s reference to the “law of war” encompasses crimes under the U.S. common law of war as well, thus making conspiracy triable by military commission prior to 2006.44 The court refused to “hold that . . . precedent conclusively establish[es] conspiracy” as triable under § 821,45 but it concluded that any Ex Post Facto Clause error was not plain.46 The court thus rejected Bahlul’s Ex Post Facto Clause challenge to his conspiracy conviction47 and remanded his case back to the D.C. Circuit panel to consider four other issues on appeal.48
In finding conspiracy to be a war crime under § 821 of the Uniform Code of Military Justice (UCMJ), the court determined, under a plain error standard of review,49 that “law of war” may include crimes not only under international law — which do not include conspiracy — but also under the “U.S. common law of war.” Such an interpretation would be problematic for two reasons: First, it would incorrectly broaden the ambit of the statute because it runs counter to judicial precedent and because Congress has never before recognized the existence of this category of war crimes. Second, it ignores normative reasons in favor of finding that Congress did not intend this interpretation; the recognition of a so-called “domestic law of war” in this statute has the potential to undermine efforts to standardize the law of war and poses dangers to American service members abroad. For these two reasons, then, this interpretation should be rejected if it were considered on de novo review.
First, interpreting § 821’s reference to the law of war to include both international law and the U.S. common law of war would misconstrue both judicial precedent interpreting this exact phrase and congressional intent. It is well established that conspiracy is not now, and has never been, a war crime under international law.50 Thus, to suggest that § 821 allocated prosecution of conspiracy to military commissions — in other words, that it considered such an offense to be under the “law of war” — Judge Henderson had to look beyond international law to a new category: the “U.S. common law of war.” The resort to this category would upend nearly seventy years of precedent interpreting the term “law of war” as referring to the branch of international law aiming to standardize the conduct of war among nations. The Supreme Court first interpreted the term “law of war” in 1942 in Ex parte Quirin,51 examining the predecessor statute to § 821 — Article 15 of the Articles of War52 — which used the same relevant language. The Quirin Court concluded that Article 15 conferred jurisdiction to try offenses “according to the rules and precepts of the law of nations, and more particularly the law of war.”53 Four years later, the Yamashita54 Court confirmed the law of war’s standing as a “branch of international law,”55 consulting the Hague Conventions and the Geneva Conventions, the two predominant sources of the law of war at that time.56 With these precedents established when drafting § 821, Congress likely was acutely focused on “law of war” as an international law concept.57
The precedents cited in Bahlul do not persuasively suggest a contrary congressional intent that “law of war” may encompass the U.S. common law of war. The D.C. Circuit, and the government, invoked the Hamdan I plurality’s mention that the “UCMJ conditions the President’s use of military commissions on compliance . . . with the American common law of war” as well as on international law.58 But the Hamdan I plurality’s reference to “the American common law of war” intended such domestic precedents to be “an additional constraint on, not an alternative basis for,” the jurisdiction of military commissions within § 821.59 Also, even the domestic precedents the government cites as establishing such a “common law” do not advance its argument. These commissions often exercised dual jurisdiction over both law-of-war crimes and criminal offenses under martial law,60 and so the commissions may not have considered the domestic substantive issues for law-of-war violations. The inconclusive nature of these early common law precedents makes it unlikely that Congress would incorporate them into § 821. Indeed, resort to mostly Civil War precedents as evidence of what the 1956 Congress that enacted § 821 would have understood “law of war” to mean is unpersuasive, given that the modern law of war did not emerge fully until after World War II.61
Second, the normative risks of such an interpretation provide further evidence that Congress did not intend to include domestic common law in the term “law of war” in § 821. Recognizing a U.S. common law of war would risk dismantling the notion of the “law of war” as a universally recognized subset of international law.62 From its earliest conceptions, the development of international law envisioned nations “reciprocally conform[ing] to general rules” as a means to constrain violent state behavior.63 The United Nations War Crimes Commission in 1949 definitively articulated the nature of a war crime as “not a crime against the law or criminal code of any individual nation” but “of universal application.”64 That each country could prosecute enemy combatants under its own domestic law of war contravenes “the very reciprocal nature” of the international law of war binding all parties.65 This would risk the balkanization of international law into various and possibly inconsistent domestic common laws of war,66 dismantling the international law of war project that has aimed to universalize the conduct of war since at least 1949.
Additionally, Congress would have recognized that allowing prosecutions under a U.S. common law of war would put American service-members at risk of prosecution under an indeterminate foreign “common law of war.”67 The “unilateralist impulse” that undergirds the government’s theory of a U.S. common law of war is yet “another manifestation of the United States’s view that international law should not constrain its ability to wage a global armed conflict against al Qaeda.”68 This approach would pose serious risks for Americans. First, American military prosecutors, judges, and other legal actors could face foreign prosecution “for the war crime of denial of a fair trial” — an offense recognized under Common Article 3 of the 1949 Geneva Conventions and in the Rome Statute — for prosecuting crimes by military commission that are not recognized as war crimes.69 Second, foreign adversaries could assert their own common law of war to try captured American personnel, with tremendous indeterminacy ex ante about what acts are prohibited.70
Therefore, interpreting “law of war” in § 821 to encompass a U.S. common law of war would defy seventy years of Supreme Court precedent and Congressional intent to further the stability and universality of the international law of war.