Washington ? The Supreme Court ruling on Guantanamo puts the brakes on what has been a sharp expansion of executive powers and raises fresh questions about other aspects of President Bush’s war-on-terror policy.

The 5-3 decision was a frontal assault on Bush’s tactics and a reaffirmation of the court’s own role in a system where power is shared among three branches of government.

“What it says is that the court has a viable interest in remaining the ultimate authority on the law,” said Charles Rose, a constitutional law professor at Stetson University College of Law in Gulfport, Fla.

Other administration anti-terror programs, including a warrantless eavesdropping program that worries even some Republicans, “are based on the same interpretation of presidential authority in a time of war” rejected in the Guantanamo case, Rose said.

Politically, the ruling comes at a bad time for Republicans. It puts Bush allies back on the defensive in a congressional election year over secretive war-on-terror initiatives. It could also help offset recent momentum from political progress in Iraq.

Bush immediately pledged to work with Congress “to have a military tribunal to hold people to account” that would meet the court’s objections. But neither politicians, legal scholars nor Bush’s own advisers suggested getting Congress to go along would be an easy task.

“This is not a decision that lends itself to a very quick disposition,” said White House press secretary Tony Snow.

Snow said the president had not set out to increase his powers but was caught between the Constitution and his obligations to the nation as commander in chief. The war on terror is “raising questions that are fairly new and people are wrestling with,” Snow said.

The court ruled on Thursday that Bush overstepped his authority in setting up military tribunals for war-crimes trials at the U.S. prison camp at Guantanamo Bay, Cuba. The justices cited violations of U.S. and international standards on prisoner rights. They also rejected an effort by Congress to strip the court of jurisdiction over habeas corpus appeals by Guantanamo detainees.

Legal and presidential scholars saw the decision as a check on the president’s assertion of expanded wartime powers.

They likened it to the court’s 1952 rejection of President Truman’s efforts to take over a strike-closed steel mill by claiming its steel production was necessary to the U.S. war effort in Korea. Similarly, the Supreme Court rejected President Nixon’s claim in the early 1970s of broad wartime power to authorize warrantless wiretap surveillance of domestic groups opposed to the Vietnam war, such as the Black Panthers.

The president and Vice President Dick Cheney have aggressively defended anti-war programs that have been criticized by Democrats, human rights groups and many legal scholars.

They have argued that increased surveillance of Americans and the holding of detainees without charges were part of inherent expanded powers that all presidents receive during times of war.

In recent days, they also have criticized the news media, particularly The New York Times, for disclosing once-secret programs including the use of an international database to track financial transactions.