A welcome rebuke.

Byline: The Register-Guard

Since Sept. 11, 2001, President Bush has acted if there are absolutely no limits on his powers in the war on terror.

For the second time in two years, the U.S. Supreme Court has bluntly informed the president that's not the case, at least when it comes to the handling of "unlawful combatants." While there is no question that presidents have more power in wartime, they cannot ignore the delicate but essential balance that allows the government's three branches to review and check each other's powers.

The court's ruling was historic in nature and scope, and provides a welcome check to an administration that in its prosecution of the war on terror has become dangerously imperial. Sen. Patrick Leahy, D-Vermont, was right to call the decision "a triumph for our constitutional system of checks and balances."

The case before the court involved Osama bin Laden's former driver, Salim Ahmed Hamdan, who challenged the administration's decision to try him in a makeshift military tribunal that lacked the basic protections accorded defendants in a court-martial, or as required under the Geneva Conventions.

By a 5-3 vote, the court said Bush did not have authority to set up the tribunals at the prison camp at Guantanamo Bay. The court also ruled that the tribunals themselves were illegal under U.S. military justice law and international law.

The court dealt the president another setback by ruling that the Geneva Conventions do apply to the conflict against al-Qaeda and that all detainees must therefore be treated humanely "in all circumstances."

The Bush administration has justified its glaring failure to provide suspected terrorists with the bare minimum of protections normally accorded prisoners of war by insisting that the conventions were intended to serve as a treaty between sovereign states and do not apply to members of an amorphous terrorist network such as al-Qaeda.

In a related decision two years ago, the court ruled that Guanta- namo detainees had the right to challenge their indefinite detention in U.S. courts. The administration sidestepped that decision by persuading an appallingly compliant Congress to pass a law restricting inmates' ability to pursue those legal challenges.

The court's new ruling also torpedoes that law - and the disturbing notion that Congress can retroactively revoke someone's right to their day in court.

In the wake of Thursday's ruling, Bush immediately pledged to work with Congress to create a tribunal system that will pass judicial scru- tiny.

Lawmakers should accept his offer but must show more backbone and constitutional resolve than they have in their previous dealings with the administration. Congress should also exercise its long-dormant oversight responsibility over other administration anti-terror initiatives, including the warrantless eavesdropping program, which are based on the same erroneous assumption that the president has limitless wartime powers.

Meanwhile, the ruling leaves Bush without any excuses for continuing to operate the Guantanamo Bay prison. The court didn't order its closure, but its ruling thoroughly undermined the administration's rationale for establishing the facility.

As international condemnation of Gitmo has grown, Bush has said he is eager to close the prison but insisted he first had to wait for the court to rule in the Hamdan case. Now, the president has his ruling. He should shut down Guantanamo, and either bring its detainees to justice in the United States or return them to their home countries.

The Bush administration defied the Constitution and international law by pursuing tribunals that made a mockery of this nation's ideals of justice and the rule of law. The court's ruling is the first step in restoring the moral and constitutional authority that should be this country's most effective weapon against terrorism.