In June 2006, the Supreme Court ruled in the case of Hamdan v. Rumsfeld (548 U.S. 557) that Al Qaeda prisoners were entitled to the Geneva Conventions’ protections against humiliating and degrading treatment, and “outrages on personal dignity.” And the Court ruled that the original military commission system for Guantanamo Bay violated the U.S. Constitution and the Geneva Conventions.
Following this ruling, officials in the Bush Administration were greatly concerned about their criminal legal liability. Both the officials who authorized “grave breaches” of laws governing treatment of prisoners of war, and those who engaged in torturing Al-Qaeda detainees feared being criminally prosecuted–as this is prohibited by the Geneva Conventions and the U.S. War Crimes Act (1996).
But Congress obliged the Administration (with the help of a dozen Democrats) by amending the War Crimes Act (WCA) with the Military Commissions Act (MCA, 2006) which provided legal immunity retroactively. The MCA limited the scope of the WCA and the Geneva Convention, and it provided legal immunity – beginning Sept. 2001 – to U.S. personnel who engaged in “any authorized conduct which was undertaken with the reasonable (though mistaken) belief that such conduct was legal.” (Michael John Garcia. The War Crimes Act: Current Issues, Congressional Research Service, Jan. 22, 2009)