The Bush administration ran into skepticism from the Supreme Court on Tuesday as justices heard debate over a landmark war powers dispute testing the legal rights of enemy combatants held at Guantanamo Bay, Cuba.

At issue were military tribunals set up by the White House to try suspected terrorists, including Salim Hamdan, said to be the driver for Osama bin Laden, in the wake of the Sept. 11, 2001 attacks. Opponents claim the tribunals are an unlawful exercise of executive branch authority.