WASHINGTON — The Bush administration argued in the Supreme Court yesterday that foreign terrorism suspects held at Guantanamo Bay have sufficient opportunities to challenge their confinement, the third round of high court review of the detentions.

The measures set out in American law for the 305 men to contest their detention is a “remarkable, remarkable liberalization” of the protections historically afforded foreigners held by America somewhere other than on American soil, Solicitor General Paul Clement said.

But attorney Seth Waxman, representing the detainees, portrayed the case as a fundamental test of the American system of justice. Many of the prisoners “have been held … for six years,” he said.

Under the current system, “they have no prospect” of being able to challenge their detention in any meaningful way, Mr. Waxman, who held Mr. Clement’s job during the Clinton administration, said. The justices, who ruled for the detainees in two prior decisions, subjected both Messrs. Clement and Waxman to a barrage of questions.

Chief Justice Roberts and Justice Scalia pressed Mr. Waxman on whether the detainees are entitled to hearings in civilian courts.

“Show me one case” down through the centuries where circumstances similar to those at Guantanamo Bay entitled an alien to challenge his detention in civilian courts, Justice Scalia said.

Justice Roberts challenged Mr. Waxman’s argument that the duration of detention is important. But most questions from the justices seemed to accept that the detainees have some rights and focused on whether procedures in place are adequate.

Justice Kennedy, considered a pivotal vote in the case, raised the possibility of returning the issue to the U.S. Court of Appeals for the District of Columbia Circuit, where the detainees’ status as enemy combatants is undergoing a highly restrictive form of review. Mr. Waxman argued that such a move would simply cause more delays in deciding the prisoners’ fate. Mr. Clement said the appeals court would be an appropriate forum for resolving the issue.

Lawyers for the foreign detainees contend the courts must get involved to rein in the White House and Congress, which changed the law to keep the detainee cases out of American courts after earlier Supreme Court rulings. The most recent legislation, last year’s Military Commissions Act, strips federal courts of their ability to hear detainee cases. Mr. Waxman, the top Supreme Court lawyer during the Clinton administration, said that “after six years of imprisonment without meaningful review, it is time for a court to decide the legality” of their confinement.

The detainee case drew several hundred spectators who lined up outside the courthouse in a light snow. About 50 had camped out overnight for a chance to get inside to hear the arguments in the third case the Supreme Court has heard since 2004 on the administration’s detention program.

Meanwhile, two dozen protesters, some in orange prison-like jumpsuits, chanted and waved signs.

“Restore habeas corpus!” they intoned, referring to the right to court review of the legality of detention, the heart of the argument before the high court.

Mr. Clement said foreigners captured and held outside the United States “have no constitutional rights to petition our courts for a writ of habeas corpus,” a judicial determination of the legality of detention.

The case could turn on whether the court decides that Guantanamo is essentially American soil, which would make the case for detainee rights stronger.

America has no plans to put most of those held at Guantanamo on trial. Three detainees face charges under the Military Commissions Act, and the military has said it could prosecute as many as 80.

[Meanwhile, despite sweeping measures to prevent suicides among the 305 prisoners at Guantanamo, a detainee slashed his throat with a sharpened fingernail recently and could have bled to death if guards hadn’t rushed to his aid, officers disclosed Tuesday. The apparent suicide attempt in November in a shower at the maximum-security Camp 6 prison was one of dozens known to have occurred since prisoners were first brought to the camp nearly six years ago.]