WASHINGTON -- The government can't throw out prisoners' constitutional rights to make their case in court just because the country faces new threats in the war on terrorism, an attorney for foreign-born detainees argued Tuesday in the Supreme Court's first case arising from the Sept. 11 attacks.

"It's been plain for 215 years," lawyer John Gibbons argued. The government, he said, cannot create a "lawless enclave" where no court, American or otherwise, can check up on things.

"The United States is at war," responded Theodore Olson, the Bush administration's top Supreme Court lawyer.

Foreigners held at the Navy's prison camp at Guantanamo Bay, Cuba, want the Supreme Court to give them a legal right "that is not authorized by Congress, does not arise from the Constitution, has never been exercised by this court," said Olson, himself a symbol of the cost of terrorism.

Olson's wife, Barbara, was killed aboard the jet that slammed into the Pentagon in September 2001. She called him on her cell phone minutes before the crash, and reported the plane had been hijacked.

The justices seemed deeply divided over the fate of more than 600 men from 44 countries who have been held for more than two years at the Guantanamo camp, and about the underlying questions concerning presidential powers in wartime.

"I'm still honestly most worried about the fact that there would be a large category of unchecked and uncheckable actions dealing with the detention of individuals that are being held in a place where America has the power to do everything," said Justice Stephen Breyer.

Two and a half years after the Sept. 11 attacks, the high court is starting small, with a simple question about whether federal judges can even hear the complaints of the Guantanamo prisoners.

Next week, the court takes up two related cases that may hit closer to home for many Americans. Those cases test President Bush's power to detain U.S. citizens for long periods without charges, and with virtually no access to the outside world.

The terrorism cases before the Supreme Court this year will draw some boundaries for White House and military authority in a war without defined opponents or a clear end.

The Kuwaiti, British and Australian prisoners at issue in Tuesday's case were swept up by U.S. forces during fighting in Afghanistan and Pakistan in the weeks after the jetliner attacks that killed thousands in New York, Virginia and Pennsylvania.

The Supreme Court's answer, due by late June, will not settle whether the men are dangerous terrorists or, as their lawyers contend, innocent victims of circumstance.

Justice Anthony M. Kennedy, a centrist whose vote may be pivotal, appeared skeptical at times that the government could simply declare the courthouse door closed to the prisoners.

True, the men are not U.S. citizens with clear rights to petition their government, Kennedy said, but the law "doesn't talk about citizens. It says prisoners held under the authority of the United States."

On the other side, Chief Justice William H. Rehnquist and Justice Antonin Scalia seemed convinced that federal courts cannot referee every complaint from foreigners held abroad.

The Supreme Court is also no place to write some detailed new rule book for the government to follow, Scalia said. He was speaking to Olson, but his real audience was Breyer, seated at the opposite end of the bench.

"We have only lawyers before us," Scalia said. "We have no witnesses. We have no cross examination. We have no investigative staff."

Central to the case is the reality of U.S. control in Guantanamo. Leased from Cuba since 1903, the base is independent of the communist country that surrounds it. As a legal matter, however, the Supreme Court must decide whether Cuba's technical sovereignty over the land means the United States courts are off-limits to prisoners.

American courts must have jurisdiction, because only American law and American authority govern what happens at Guantanamo, Gibbons argued.

"Cuban law has never had any application inside that base. A stamp with Fidel Castro's picture on it wouldn't get a letter off the base."