The Roberts Court ruled 5–3 in Hamdan v. Rumsfeld (2006) that the executive branch (the George W. Bush administration) exceeded its constitutional authority in establishing military commissions to try the so-called “enemy combatants” held at the Naval base in Guantanamo Bay, Cuba. The Court determined that such military commissions, created without approval from the U.S. Congress, did not conform to the procedures established by the Uniform Code for Military Justice or the Geneva Conventions, which contain procedures for dealing with prisoners of war. The Court’s opinion means that the government must either seek legislation from Congress authorizing such military commissions or try individuals like Hamdan according to established rules of military justice. In a concurring opinion, Justice Stephen Breyer wrote that there was nothing to stop the president from urging Congress to pass legislation authorizing such military commissions.

Justices Clarence Thomas, Antonin Scalia, and Samuel Alito dissented, arguing that the Court should show more deference to the executive branch during the War on Terror. In his dissenting opinion, Justice Thomas termed the Court’s opinion “dangerous.”