WASHINGTON — U.S. citizens overseas who take up arms against their country can be held as enemy combatants without the constitutional rights afforded other Americans, a federal appeals court ruled Wednesday.

The decision by a three-judge panel of the 4th U.S. Circuit Court of Appeals in Richmond, Va., affirms the government's authority to detain indefinitely American citizens captured in foreign battles or those who participate in terrorist attacks against U.S. interests.

But the ruling stopped short of approving those same powers over Americans arrested on U.S. soil, which legal experts said leaves a major question for courts to settle in the future.

"They have substantially cooled what has been a legal hot potato," said Michael Greenberger, a former senior Justice Department official in the Clinton administration who now directs the University of Maryland's Center for Health and Homeland Security.

The appeals decision overturned a lower court's ruling that 22-year-old Yaser Esam Hamdi, a Louisiana native captured in Afghanistan in November 2001, must see the government's evidence supporting its claims that he fought with Al Qaeda and Taliban forces against the United States.

Courts, the judges ruled, must be "highly deferential" to the government during wartime, even an unconventional war such as that against global terrorism. Hamdi, they added, is being held under "well-established laws and customs of war."

"The fact that he is a citizen does not affect the legality of his detention as an enemy combatant," the judges said.

Attorney General John Ashcroft applauded the decision, calling it "an important victory for the president's ability to protect the American people in times of war."

"Detention of enemy combatants prevents them from rejoining the enemy and continuing to fight against America and its allies, and has long been upheld by our nation's courts, regardless of the citizenship of the enemy combatant," Ashcroft said in a statement.

Frank Dunham Jr., a lawyer hired by Hamdi's family who has represented him in the case but has not met with him, did not immediately return calls seeking comment.

Constitutional activist called the decision an abdication of the judicial system's duties to protect the rights of U.S. citizens. Some compared it to the decisions upholding internment of Japanese-Americans during World War II, when the government was given broad latitude and later was forced to apologize for mistreating citizens.

"It's a we'll-look-the-other-way decision which undermines the system of checks and balances put in place in this country to ensure that power is not abused," said Elisa Massimino, who heads the Washington office of the Lawyers Committee for Human Rights.

Other experts questioned the court's rejection of arguments that Hamdi should be treated either as a prisoner of war, subject to rights under the Geneva Convention, or prosecuted for crimes using traditional methods.

"This decision condones government's creation of a constitutional no man's land," said Susan Herman, law professor at Brooklyn Law School.

According to the government, Hamdi was captured after his Taliban unit was overrun by Northern Alliance forces. He was at the prison uprising in Mazar-e-Sharif where fellow U.S. citizen John Walker Lindh was captured and later was transported with hundreds of others to a prison at the U.S. Navy base at Guantanamo Bay, Cuba.

Hamdi was transferred to the naval brig in Norfolk, Va., after it was discovered he was born in Louisiana to Saudi parents. Hamdi and his family returned to Saudi Arabia while he was a toddler, but he never renounced his U.S. citizenship.

The appeals court in Richmond, Va., agreed that the case raises serious questions about the rights of citizens but concluded that, in wartime, the government's authority is supreme in deciding who may be held indefinitely.

Hamdi was "squarely within the zone of active combat" when captured and was in possession of an AK-47 rifle, the judges said. They added that courts have only limited authority to intervene in such national security matters.

"Any effort to ascertain the facts concerning the petitioner's conduct while amongst the nation's enemies would entail an unacceptable risk of obstructing war efforts authorized by Congress and undertaken by the executive branch," the judges said.

The court did not address questions about U.S. citizens arrested as enemy combatants in this country. The government has classified as a combatant Jose Padilla of Chicago, who was arrested at O'Hare Airport after returning from Pakistan.

Authorities accused Padilla of plotting to detonate a radioactive "dirty bomb." A federal judge in New York has ruled that Padilla should have the right to argue he is being improperly detained.

The three circuit judges who unanimously decided the Hamdi case were James Harvie Wilkinson III and William W. Wilkins, both appointed by President Reagan, and William B. Traxler, who was appointed by President Clinton.