A federal appeals court ruled Tuesday that foreign-born prisoners seized as potential terrorists and held in Guantanamo Bay may not challenge their detention in U.S. courts, a key victory for President Bush's anti-terrorism plan.

The U.S. Court of Appeals for the District of Columbia Circuit ruled 2-1 that civilian courts no longer have the authority to consider whether the military is illegally holding the prisoners -- a decision that will strip court access for hundreds of detainees with cases currently pending.

"The arguments are creative but not cogent. To accept them would be to defy the will of Congress," wrote Judge A. Raymond Randolph in the 25-page opinion, which was joined by Judge David B. Sentelle. Both are Republican appointees to the federal bench.

Barring federal court access was a key provision in the Military Commissions Act, which Bush pushed through Congress last year to set up a system run by the Defense Department to prosecute terrorism suspects.

Attorneys for the detainees immediately said they would appeal the ruling to the Supreme Court, which last year struck down the Bush administration's original plan for trying detainees before military commissions.

"We're disappointed," said Shayana Kadidal of the Center for Constitutional Rights. "The bottom line is that according to two of the federal judges, the president can do whatever he wants without any legal limitations as long as he does it offshore."

A spokesman for the Justice Department praised the decision.

"The decision reaffirms the validity of the framework that Congress established in the MCA permitting Guantanamo detainees to challenge their detention" through military hearings coordinated by the Defense Department, said spokesman Erik Ablin.

Under the commissions act, the government may indefinitely detain foreigners who have been designed as "enemy combatants" and authorizes the CIA to use aggressive but undefined interrogation tactics.

Most criticized by Democrats and civil libertarians was a provision that stripped U.S. courts of the authority to hear arguments from detainees who said they were being held illegally. The law instead authorizes three-officer military panels to review whether there is sufficient evidence to justify the detention.

Attorneys argued that the detainees aren't covered by that provision and the military panels don't meet minimum standards of detainees' due process rights. But in Tuesday's ruling, the D.C. Circuit panel said the new law did apply.

A spokeswoman for Democratic Sen. Patrick Leahy, chairman of the Judiciary Committee, said he was accelerating efforts to pass a revision to the law that would restore detainees' legal rights, noting that some 12 million lawful permanent residents currently in the U.S. could also be stripped of rights.

The new provision, introduced by Leahy and then-Judiciary Chairman Arlen Specter, R-Pa., narrowly failed last year on a 48-51 vote.

"The Military Commissions Act is a dangerous and misguided law that undercuts our freedoms and assaults our Constitution by removing vital checks and balances designed to prevent government overreaching and lawlessness," Leahy, D-Vt., said in a statement.

U.S. citizens and foreigners being held inside the country normally have the right to contest their detention before a judge. The Justice Department said foreign enemy combatants are not protected by the Constitution.

Judge Judith W. Rogers dissented, saying the cases should proceed. She argued that the military hearings -- known as Combatant Status Review Tribunals, or CSRTs -- deprive detainees of critical due process rights by putting the legal burden on detainees to prove they do not pose a terrorist threat.

"District courts are well able to adjust these proceedings in light of the government's significant interests in guarding national security," wrote Rogers, a Clinton appointee. "More significant still, continued detention may be justified by a CSRT on the basis of evidence resulting from torture."

Rep. Ike Skelton, D-Mo., who chairs the House Armed Services Committee, said he is concerned about whether military hearings offer detainees the legal protections and will launch a congressional review.

"The last thing that we would want is to convict an individual for terrorism and then have that conviction overturned because of fatal flaws in the Military Commissions law passed in the previous Congress," he said.

Jonathan Hafetz, an attorney at the Brennan Center for Justice, said the ruling sends the wrong message about justice to U.S. citizens and the international community.

"It's a terrible ruling that contradicts centuries of Anglo-American history and allows the indefinite detention of innocent people without charge or judicial review," he said.