As others have noted, the Supreme Court left open a number of pressing questions in its Boumediene opinion. Most intriguing from my perspective is the choice of law issue addressed to the question of which body (or bodies) of law will apply to determine the lawfulness of the detainees’ detentions in the forthcoming habeas proceedings. To this issue, the Court merely noted that: “It bears repeating that our opinion does not address the content of the law that governs petitioners’ detention. That is a matter yet to be determined” (p. 69).
The question of which law governs is not an obvious one. In all cases, of course, U.S. law will govern the question of when and how an individual may be detained by U.S. government agents. In certain cases, however, international law speaks to the same question.
International humanitarian law (IHL) in particular is relevant to those individuals detained while participating in hostilities in Afghanistan prior to the establishment of a new government there (i.e., between October 7, 2001, and June 19, 2002). During this time, the conflict in Afghanistan was an “international armed conflict” within the meaning of Article 2 of the 1940 Geneva Conventions. (According to that provision, the Conventions “apply to all cases of declared war or of any other armed conflict which may arise between two or more of the High Contracting Parties, even if the state of war is not recognized by one of them”). By contrast, individuals detained after June 19, 2002—when the conflict in Afghanistan was no longer an “international armed conflict” as defined by IHL—are only subject to the IHL governing non-international armed conflicts. (From that date onward, the conflict was no longer between High Contracting Parties; although multiple High Contracting Parties remain involved in the conflict, they are aligned on the same side). Individuals detained outside of the theater of war, like the Boumediene petitioners who were detained in Bosnia-Herzegovina, likely fall outside of IHL altogether.
All of these individuals are presumptively protected by human rights law, which applies in times of peace and war. Article 9(1) of the International Covenant on Civil and Political Rights states: “No one shall be subjected to arbitrary arrest or detention.” The precise relationship between IHL and human rights law remains inchoate, although it is clear that in situations of armed conflict, both bodies of law will apply in a complementary fashion. For example, IHL as the lex specialis can add content to the determination when a detention is “arbitrary” within the meaning of human rights law.
This leads to the question of what substantive standards govern the legality of the detention of individuals under these various bodies of international law, assuming they apply. Under IHL, the specific rules applying to individual detainees depend upon conflict classification, the relationship of such individuals to the conflict, and the circumstances of their capture. In particular, in international armed conflicts, there are regimes for interning prisoners of war as a matter of course and for interning aliens in the territory of the Detaining Power or in occupied territory who present security risks.
By contrast, the rules governing non-international armed conflicts do not create a specific regime for the detention of individuals. Thus, the procedures applicable to their detention are governed by domestic criminal law as tempered by relevant provisions of international human rights law. The International Covenant on Civil and Political Rights, while setting forth a general prohibition against arbitrary detention and a right to habeas corpus, does not provide much in the way of substantive standards to determine when a detention is arbitrary. Clearly detentions not in accordance with procedures established by law would qualify (Art. 9(1)).
This choice of law question will also force the lower courts to confront §5 of the Military Commission Act, assuming it applies to pending cases. This provision states:
No person may invoke the Geneva Conventions or any protocols thereto in any habeas corpus or other civil action or proceeding to which the United States, or a current or former officer, employee, member of the Armed Forces, or other agent of the United States is a party as a source of rights in any court of the United States or its States or territories.
Strong arguments exist that this clause—if it indeed applies to situations in which detainees are contesting the validity of their detentions—violates fundamental separation of powers principles by constraining the sources of law and rules of decision courts can invoke in deciding matters before them, as convincingly advanced by our colleague Steve Vladeck in his amicus brief in the cases.