The tarnished U.S. human rights image faces a major test this week as the Supreme Court considers whether terrorism suspects held for years without charges at Guantanamo Bay are wrongly detained.

The court's nine justices on Wednesday are to hear the appeal of Guantanamo prisoners who say a 2006 law unconstitutionally denies them a meaningful way to challenge in court their detention at the U.S. Naval Base on Cuba.

The case is being watched by governments and human rights activists around the world, who say President George W. Bush has overreached his powers and trampled on rights in the war on terrorism he launched after the September 11, 2001, attacks.

"The rule-of-law, humanitarian and human rights principles at stake in this case are the very principles which the coalition of liberal democracies together seek to uphold and defend in the 'war on terror,'" British and European parliament members said in one of the many outside briefs urging the Supreme Court to rule in favor of the detainees.

The Bush administration told the court the Guantanamo prisoners receive fair treatment and a chance to make their case before a military tribunal, with a limited appeals court review. But it said the Constitution's "habeas corpus" rights for prisoners to seek a court review of their detention do not apply to foreigners held outside the country.

"The detainees now enjoy greater procedural protections and statutory rights to challenge their wartime detentions than any other captured enemy combatants in the history of war. Yet they claim an entitlement to more," the Justice Department said in its brief on the case.