"Counsel for a detainee has a 'need to know' the classified information relating to his client's case," the appeals court ruled. "The government may withhold from counsel, but not from the court, certain highly sensitive information."

The appeals court decision is likely to be considered by the Supreme Court as it decides whether detainees should have greater access to U.S. civilian courts.

When detainees are brought before military CSRTs, they are not allowed to have lawyers with them and the Pentagon decides what evidence to put forward. Unlike in criminal trials, there is no obligation for the government to turn over evidence that the defendant might be innocent. If the military reviewers determine a prisoner is an enemy combatant, he can challenge that designation in the U.S. Circuit Court of Appeals for the District of Columbia.

During that appeal, government attorneys argued, federal judges have the authority only to review the evidence the Pentagon had chosen to put forward during the CSRT hearing.

Without all the information, the appeals court said, deciding whether the military reviewers acted appropriately would be like trying to figure out the value of a fraction without knowing both numbers.

"The court has resoundingly rejected the government's effort to control the record and to limit an investigation into the truth," said attorney Sabin Willett, who argued the case.

Washington, D.C., attorney David Remes said, however, that the court's decision "will turn out to be a prescription for endless litigation in these cases."

"The court said that its review goes beyond the information presented to the Combatant Status Review Tribunals, but the court never explains how it can determine what that information might be," said Remes, who represents 17 Guantanamo Bay detainees.

Remes also said that "it's clear from the decision that the review under the Detainee Treatment Act falls short of constitutionally required habeas corpus review." The Supreme Court will soon consider whether detainees have the right to challenge their detention in federal courts. That right was stripped away by the most recent terrorism law.

Remes said the ruling contains restrictions that "will seriously cripple the lawyer-client relationship." Under the decision, detainees and their lawyers must limit communications to events leading up to a detainee's capture and the conduct of CSRT proceedings relating to the detainee.

Jonathan Hafetz, an attorney involved in other detainee cases, said Friday's court ruling is only a minor improvement in a seriously flawed process.

"It's definitely better than what the government had proposed but it still doesn't provide for a meaningful process," Hafetz said.

The Justice Department argues that the detainees are being afforded more rights than required by law. The government argues that it cannot bring the detainee cases in civilian courts without jeopardizing national security.

Friday's unanimous decision was issued by Judges Douglas Ginsburg, Judith Rogers and Karen Lecraft Henderson. Rogers is a Clinton appointee. Ginsburg, the chief judge of the appeals court, is a Reagan appointee. Henderon was appointed by President Bush's father, George H.W. Bush.