“It is the policy of this administration to invoke the state secrets privilege only when necessary and in the most appropriate cases,” he said, adding that Attorney General Eric H. Holder Jr. had asked for a review of pending cases in which the government had previously asserted a state secret privilege.

“The attorney general has directed that senior Justice Department officials review all assertions of the state secrets privilege to ensure that the privilege is being invoked only in legally appropriate situations,” he said. “It is vital that we protect information that, if released, could jeopardize national security.”

The court papers describe horrific treatment in secret prisons. Mr. Mohamed claimed that during his detention in Morocco, “he was routinely beaten, suffering broken bones and, on occasion, loss of consciousness. His clothes were cut off with a scalpel and the same scalpel was then used to make incisions on his body, including his penis. A hot stinging liquid was then poured into open wounds on his penis where he had been cut. He was frequently threatened with rape, electrocution and death.”

Ben Wizner, a lawyer for the A.C.L.U., told the judges that many of the facts that the government is trying to keep secret are scarcely secret at all, since the administration’s rendition program and the particulars of many of the cases have been revealed in news reports and in the work of government investigations from around the world. “The only place in the world where these claims can’t be discussed,” Mr. Wizner said, “is in this courtroom.”

What the A.C.L.U. is asking, he said, is that the case be allowed to go forward, giving the courts a chance to decide, based on classified information revealed solely to the judge, what should be allowed to be discussed.

But Mr. Letter said that the lower court judge, James Ware, did receive classified information and came to the correct conclusion in dismissing the case last year. He urged the judges to pore over the same material, and predicted “you will understand precisely, as Judge Ware did, why this case can’t be litigated.”

In a related matter, Patrick J. Leahy, the Vermont Democrat who is chairman of the Senate Judiciary Committee, on Monday proposed the establishment of a “truth commission” to investigate the Bush administration’s treatment of detainees and other issues, like the firings of United States attorneys by the Justice Department. The commission, he said, could grant immunity to witnesses to explore the facts without the threat of criminal prosecution.