The Military Commissions Act of 2006: Examining the Relationship between the International Law of Armed Conflict and US Law

John Cerone
November 13, 2006

In Hamdan v. Rumsfeld,[1] the US Supreme Court held that the military commission prosecuting Salim Ahmed Hamdan, an alleged Al-Qaeda affiliate captured during the US invasion of Afghanistan, lacked power to proceed.[2] The Court based its decision in part on its finding that the establishment of the commission and rules governing commission proceedings violated relevant provisions of US law. In so doing, the Court found the international law of armed conflict - including the standards of Common Article 3 of the 1949 Geneva Conventions - to be judicially cognizable in US courts, at least insofar as the Court construed it to be incorporated by reference in an Act of Congress.

In the wake of this decision, the Office of the US Secretary of Defense issued a memorandum noting that "[t]he Supreme Court has determined that Common Article 3 to the Geneva Conventions of 1949 applies as a matter of law to the conflict with Al Qaeda," and requesting Defense Department leadership to take steps to ensure compliance by all personnel. Shortly thereafter, the Bush Administration stated its intention to go to the US Congress to seek authorization to reconstitute the impugned commissions in light of the Court's decision.[3]

Its efforts resulted in the enactment of the Military Commissions Act of 2006 (MCA),[4] which was signed into law by President Bush on October 17, 2006. This Insight focuses on the international legal dimensions of that Act.

Summary of Provisions

The MCA encompasses a wide range of measures, including provisions:

-authorizing the President to establish military commissions for the prosecution of certain offenses committed by alien unlawful combatants;

-prescribing the procedure and substantive law to be applied by the commissions;

-amending the US War Crimes Act to specify criminal violations of Common Article 3;

-retroactively eliminating the right of habeas corpus for alien enemy combatants[5] detained by the US;

-extending the prohibition under US law on cruel, inhuman, or degrading treatment or punishment to encompass all those in the custody or under the physical control of the United States,[6] regardless of nationality or physical location;

-limiting the ability of individuals to invoke the Geneva Conventions as a source of rights in certain proceedings; and

-purporting to authoritatively interpret the Geneva Conventions and to delegate further interpretive authority to the US Executive.

Many of these measures address directly or indirectly the status of the international law of armed conflict within the US legal system.[7]

The "Law of War" as US Law

The MCA makes several references to the "law of war," a phrase which is not defined in the Act. The meaning of the term within the US legal system, and within the context of the MCA in particular, is unclear. First, it may refer to the international law of armed conflict, also known as international humanitarian law or the jus in bello. Second, it could refer to this same body of international law as it is understood within the US legal system (i.e. as interpreted by those empowered under US law to do so[8]). Or, third, it could refer to the second category as supplemented or modified by other related US law, including common law, legislation, and other legal instruments. This third category would include the MCA itself.

At a minimum, the "law of war" was understood by the Hamdan Court to include the 1949 Geneva Conventions. The Supreme Court read the Geneva Conventions into the reference to the "law of war" in Article 21 of the Uniform Code of Military Justice (UCMJ). The UCMJ is a federal statute. The Supreme Court did not, however, find that the Geneva Conventions were self-executing or otherwise part of US law beyond the confines of that Article.

The MCA does not directly address the status of the Conventions as US law. It does, however, preclude any "alien unlawful enemy combatant" from "invok[ing] the Geneva Conventions as a source of rights" in prosecutions before the military commissions envisioned by the MCA.[9] It also says that no person may invoke the Conventions in any habeas corpus proceeding or other civil action as a source of rights against the US government or those acting on its behalf.[10]

The Act also appears to limit the power of US courts to interpret the Geneva Conventions. The MCA confers upon the President "the authority for the United States to interpret the meaning and application of the Geneva Conventions and to promulgate higher standards and administrative regulations for violations of treaty obligations...."[11] These interpretations are to be issued in the form of Executive Orders and shall be authoritative as a matter of US law, in the same manner as other administrative regulations. To the extent this authority is used by the President, it might restrict the scope of interpretation otherwise afforded to the judicial branch.[12] This part of the Act, however, expressly recognizes the constitutional functions of the judicial branch.[13] Article III of the Constitution vests the judicial power of the United States in the Supreme Court and lower federal courts, and says that the judicial power extends to treaties of the United States.

The MCA also appears to stipulate certain interpretations.[14] For example, the Act states that "[a] military commission established under this chapter is a regularly constituted court, affording all the necessary judicial guarantees which are recognized as indispensable by civilized peoples' for purposes of common Article 3 of the Geneva Conventions."[15] This attempts to preclude the possibility of a US court finding that the newly authorized commissions were not such "regularly constituted" courts, as the Supreme Court did with respect to the earlier commissions in Hamdan. The Supreme Court might hold that it is still able to make such findings under its constitutional power.

Another stipulated interpretation appears in the Section of the MCA that amends the US War Crimes Act by criminalizing certain serious violations of Common Article 3. The Act provides that this criminalization "fully satisf[ies] the obligation under Article 129 of the Third Geneva Convention for the United States to provide effective penal sanctions for grave breaches which are encompassed in common Article 3 in the context of an armed conflict not of an international character."[16] It then further limits the ability of US courts to interpret the crimes by stating that "[n]o foreign or international source of law shall supply a basis for a rule of decision in the courts of the United States in interpreting the prohibitions enumerated..."[17]

Notably, however, the MCA does not state that the Geneva Conventions do not form part of US law. In addition, the US Supreme Court's Charming Betsy canon will apply to interpretation of the MCA.[18] According to this canon, an Act of Congress ought never to be interpreted to conflict with the international obligations of the United States so long as another reasonable construction is possible. Thus, the MCA would presumably be interpreted in such a way as to be consistent with the Geneva Conventions except where it clearly and irreconcilably departs.

The Content of the Law of Armed Conflict as Reflected in the MCA

The MCA authorizes the President to create military commissions to prosecute alien unlawful enemy combatants and elaborates a code of crimes within the commissions' subject matter jurisdiction. In defining unlawful enemy combatants as well as the various enumerated crimes, the Act draws heavily on the language of the Geneva Conventions. At the same time, it does so selectively, at times omitting certain provisions or omitting phrases within otherwise incorporated provisions. For example, the definition of a lawful combatant is drawn from the definition of prisoners of war in Article 4 of the Third Geneva Convention. However, it narrows that definition, conversely expanding the definition of an unlawful combatant, by excluding certain categories of individuals.[19]

The code of offenses also illustrates a broader tension within the US understanding of the law of armed conflict. Many of the enumerated crimes are composites of rules drawn from the law of international armed conflict and the law of non-international armed conflict. While these two bodies of law have converged to a degree, significant differences remain.[20] Thus, any attempt to blend these bodies of law must be undertaken with great care, particularly when prescribing criminal liability for their violation.

In some cases, the code criminalizes[21] conduct traditionally understood as violating the law of international armed conflict. However, because the US views the conflict with Al-Qaeda as a non-international armed conflict, many of the enumerated crimes would not qualify as war crimes as traditionally understood given the narrower scope of rules applicable in such conflicts under common Article 3 of the Geneva Conventions.

The definitions of some of the crimes include an express reference to "the law of war." For example, the MCA criminalizes the "intentional killing of one or more persons, including lawful combatants, in violation of the law of war." As the killing of lawful combatants who are placed hors de combat is addressed elsewhere in the MCA, it would seem that this provision is meant to include the killing of lawful combatants who are still taking part in the hostilities. Such killing is not of itself a violation of the law of non-international armed conflict. Certainly, international law provides no privilege to kill in a non-international armed conflict; however, this simply means that the person could be held criminally responsible under ordinary domestic law, not the law of armed conflict.[22]

Thus, the phrase "in violation of the law of war" in this context seems to impose as an additional element the violation of a rule of that body of law relating to the methods and means of battlefield killings. For example, it is possible that this provision could be construed to criminalize violations of the Hague Regulations, including, for example, the employment of prohibited weapons, to the extent this body of law has evolved through custom to apply in non-international armed conflicts.[23]

While the US is free to legislate new crimes under US law,[24] it could not prosecute new crimes on the basis of acts committed prior to the MCA's entry into force. Conscious of this issue, the MCA asserts that the crimes contained therein are "declarative of existing law" - an across-the-board assertion likely to be met with doubt by many international law authorities.[25]

A similar discord is found in the section of the MCA amending the US War Crimes Act. The impetus to amend the War Crimes Act was presumably provided by the Supreme Court's finding that Common Article 3 (which was incorporated by reference in the Act) regulated the treatment of Hamdan. As has been noted above, the Defense Department has applied the Court's ruling to the conflict with Al-Qaeda in general. The War Crimes Act previously prohibited violations of Common Article 3 in very general terms. The MCA amends the War Crimes Act to prohibit violations of Common Article 3 only if they amount to "grave breaches," and then specifically defines the crimes that constitute "grave breaches" of Common Article 3.

As noted above, the MCA stipulates that its criminalization of these violations of Common Article 3 "fully satisf[ies] the obligation under Article 129 of the Third Geneva Convention for the United States to provide effective penal sanctions for grave breaches which are encompassed in common Article 3..." The relevant part of Article 129 of that Convention reads:

The High Contracting Parties undertake to enact any legislation necessary to provide effective penal sanctions for persons committing, or ordering to be committed, any of the grave breaches of the present Convention defined in the following Article.[26]

However, the "following Article," Article 130 of the Third Geneva Convention, makes no reference to Common Article 3. Indeed, the International Criminal Tribunal for the former Yugoslavia and the Statute of the International Criminal Court recognize the existence of "grave breaches" only in the context of international armed conflicts. Thus, one could not sensibly speak of "grave breaches" of Common Article 3, in the sense of Article 129.

Finally, in enumerating the various "grave breaches" of Common Article 3, the MCA omits two prohibitions contained within Common Article 3 - the prohibition of "[o]utrages upon personal dignity, in particular, humiliating and degrading treatment" and of "[t]he passing of sentences and the carrying out of executions without previous judgment pronounced by a regularly constituted court affording all the judicial guarantees which are recognized as indispensable by civilized peoples."[27]

According to a number of US officials, the prohibition of "outrages upon personal dignity" was too vague to serve as a basis for prosecution. Nonetheless, outrages upon personal dignity have been prosecuted as such by the International Criminal Tribunals for the former Yugoslavia and Rwanda, and are included in the subject matter jurisdiction of the International Criminal Court.[28] In its place, the War Crimes Act now expressly criminalizes rape and sexual assault or abuse.

The omission of any reference to "judicial guarantees which are recognized as indispensable by civilized peoples" is significant as well. Four Justices of the US Supreme Court in the Hamdan case found that the military commission the President had established to prosecute Hamdan failed to meet that standard. Nothing in the Act has taken its place.

The MCA does state, however, that "The definitions in this subsection are intended only to define the grave breaches of common Article 3 and not the full scope of United States obligations under that Article." This tacitly acknowledges that the US is still obliged to comply with all of the prohibitions contained in Common Article 3, even though it does not regard itself as obliged to hold criminally accountable individuals who violate these prohibitions.


Under US law, the US legislature is free to deviate from the understanding of the law of armed conflict held by others. However, if it does so, it risks placing the US in default of its international obligations. Also, to the extent it purports to create criminal liability for conduct that was not prohibited under international law or US law at the time it occurred, it risks running afoul of the principle against ex post facto criminalization, as recognized in international law[29] well as US constitutional law.[30] Finally, the extent to which the Act purports to limit the power of US courts to interpret the international law of armed conflict, including by stipulating certain interpretations, may raise separation-of-powers concerns. All of these issues are likely to arise in the ongoing litigation over the detainees at Guantanamo Bay.



About the author

John P. Cerone, an ASIL member and co-chair of the ASIL Human Rights Interest Group, is Associate Professor of Law and Director of the Center for International Law and Policy at the New England School of Law.


[1] 126 S.Ct. 2749 (2006).

[2] See the July 2006 Insight "Status of Detainees in Non-International Armed Conflict, and their Protection in the Course of Criminal Proceedings: The Case of Hamdan v. Rumsfeld."

[3] International law, when recognized as part of the law applicable in US courts, has the status of, at most, ordinary federal law. This is particularly true with respect to the Hamdan Court's reading of Common Article 3, as this provision was deemed applicable as incorporated into a federal statute. Thus, it can be overridden by an Act of Congress.

[4] Public Law 109-366, 120 Stat. 2600 (Oct. 17, 2006).

[5] This provision applies to all alien enemy combatants, lawful or unlawful.

[6] This would include individuals in the custody or otherwise under the control of the CIA.

[7] Many of the law's provisions also potentially raise issues under human rights law, including the International Covenant on Civil and Political Rights, to which the US is a party. With respect to the treatment of individuals outside US territory, this raises the issue of whether the ICCPR applies extraterritorially. See the October 2005 Insight, "The Application of Regional Human Rights Law Beyond Regional Frontiers: The Inter-American Commission on Human Rights and US Activities in Iraq," and the February 2006 Insight, "Alleged Secret Detentions of Terrorism Suspects."

[8] The MCA itself delegates substantial interpretive authority to the US Executive as explained infra.

[9] MCA Section 3(a).

[10] MCA Section 5(a).

[11] MCA Section 6(a)(3)(A).

[12] While it is not unusual to confer interpretive authority on the Executive, the context here is quite different from the granting of authority to interpret US legislation. The Executive is here given the power under US law to authoritatively interpret legal instruments (i.e. the Geneva Conventions) that the US is without power to change unilaterally under international law.

[13] MCA Section 6(a)(3)(D).

[14] These stipulations may raise separation-of-powers concerns.

[15] MCA Section 3(a)(1).

[16] MCA Section 6(a)(2).

[17] The inclusion of this provision illustrates a tension in the White House attitude toward the jurisprudence of international courts. The September 2006 White House Fact Sheet explaining the President's proposed legislation sought to demonstrate the acceptability of the commission's proposed evidentiary rules by noting that similar rules have been adopted by international tribunals.

[18] See The Charming Betsy, 6 US (2 Cranch) 64, 117-118 (1804).

[19] It excludes, for example, individuals participating in a levée en masse (a spontaneous resort to arms in resistance to invading forces), codified in article 4(6) of the Third Convention. Similarly, it omits the phrase "or an authority" in its incorporation of article 4(3), which gives prisoner-of-war status to captured "Members of regular armed forces who profess allegiance to a government or an authority not recognized by the Detaining Power."

[20] Hamdan Insight, supra note 1.

[21] The term "criminalizes" is here used to denote codification as a crime for prosecution by the envisioned military commissions.

[22] In certain circumstances, particularly when a conflict is internal within a single State, a killer could be held criminally responsible under ordinary domestic law. The MCA is likely to lead to difficulties of interpretation and application because it fails to account for the implications of removing Common Article 3 from the context of an internal armed conflict and applying it to a transnational armed conflict with a non-state group.

[23] It should be noted, however, that the Act elsewhere specifically criminalizes "using treachery or perfidy," "denying quarter," and "employing poison or similar weapons." Notably, the Act does not criminalize the use of incendiary weapons.

[24] The US would likely be able to invoke the protective principle (allowing a State to prohibit and prosecute conduct outside its territory that is directed against its security or other vital interests) or passive personality principle (allowing, in limited circumstances, a State to prohibit and prosecute conduct harmful to its citizens even outside its own territory).

[25] In the section of the MCA asserting that it does not establish new crimes, but rather codifies already-existing crimes traditionally triable by military commissions, it indicates that some of the crimes "incorporate definitions in other provisions of law." 47A US Code § 950p (added by MCA Section 3). While this phrase is unclear, it seems to imply that those crimes that may not be violations of the law of war are drawn from analogous offenses under ordinary criminal law. This raises the question of how far analogy can be extended under the principle that no one shall be held guilty of an offense that did not constitute a crime, under national or international law, at the time when it was committed. It may also raise questions regarding the extraterritorial reach of domestic criminal law as they relate to this issue.

[26] Parallel language is found in each of the four Geneva Conventions. While a subsequent paragraph of Article 129 requires states parties to suppress "other breaches" of the Convention (i.e. other than "grave breaches"), that paragraph makes no mention of "effective penal sanctions.

[27] The stipulation that the MCA's criminalization of the specified violations satisfies the obligation to provide effective penal sanctions is presumably designed to prevent courts from importing these prohibitions into the War Crimes Act through a strained reading of Article 129 of the Third Geneva Convention.

[28] Article 8(2)(c) of the ICC Statute criminalizes "serious violations of article 3 common to the four Geneva Conventions of 12 August 1949" and includes almost verbatim the list of acts prohibited under Common Article 3.

[29] International Covenant on Civil and Political Rights, art. 15.

[30] US Constitution, art. 1, sections 9 & 10.