The D.C. Circuit just reversed a district court, which had granted a writ of habeas corpus to a Guantanamo Bay detainee set for prosecution in a military commission. The district court had held that the detainee was entitled to the protections of the Geneva Convention and could not be tried for violating the laws of war unless properly stripped of prisoner of war status by an appropriate tribunal, which the military commission was not.
In Hamdan v. Rumsfeld, the D.C. Circuit rejected that argument, concluding that the Geneva Convention was not self-executing, that Hamdan could not claim much of its protections because Al Qaeda was not a signatory, and that his arguments concerning the make-up of the commission were not jurisdictional and hence were subject to abstention under Schlesinger v. Councilman, 420 U.S. 738 (1975).
The three-judge panel was unanimous in reversing, with Judge Williams adding a short concurrence in which he argued that Common Article 3 of the Geneva Convention, which applies in "armed conflict not of an international character occurring in the territory of one of the High Contracting Parties" was not limited to internal civil wars, as the court's opinion concluded, but extended as a "gap-filler" to conflicts involving non-state actors, such as Al Qaeda.
Presumably, Hamdan will seek cert., but my guess is that if he does, the Supreme Court won't take the case. If Hamdan is convicted in the military commission, there should be another opportunity for the Court to hear the case if it wants, so it's likely to let the proceedings run their course.