Three of the four-member conservative bloc on the court spent much of the argument challenging former Clinton Solicitor General Seth Waxman, who represented the detainees.
Justice Antonin Scalia repeatedly asked Waxman whether "you have any precedent, U.S. or British, in which habeas corpus was granted to an alien?" Scalia rejected Waxman's argument that precedents allowing habeas on foreign territory "subject" to the United States was the real issue.
U.S. law sets up military commissions to try the foreign enemy combatants, but doesn't allow them to challenge the evidence, or even see it in most cases.
The four-member liberal bloc -- Justices John Paul Stevens, Ruth Bader Ginsburg, David Souter and Stephen Breyer -- were equally as challenging with Solicitor General Paul Clement, who spoke for the Bush administration.
How could existing U.S. law be an adequate substitute for habeas, Souter asked, "when you can't argue I've been held for six years without trial or charge."
Justice Anthony Kennedy, a probable swing vote, held his cards close to the vest. But when the conservatives badgered Waxman about whether U.S. law really applies at Guantanamo, he jokingly asked, "You're not heartened that the detainees could have access to the Cuban courts?"