WASHINGTON - Senior lawyers in the Obama administration are deeply divided over some of the counterterrorism powers they inherited from former President George W. Bush, according to interviews and a review of legal briefs.

The rift has been most pronounced between top lawyers in the State Department and the Pentagon, though it has also involved conflicts among career Justice Department lawyers and political appointees throughout the national security agencies.

The discussions, which shaped classified court briefs filed in March, have centered on how broadly to define the types of terrorism suspects who may be detained without trials as wartime prisoners. The outcome of the yearlong debate could reverberate through national security policies, including the number of people the United States ultimately detains and decisions about who may be lawfully selected for killing using drones.

“Beyond the technical legal issues, this debate is about the fundamental question of whom we are at war with,” said Noah Feldman, a Harvard law professor . “The two problems most plaguing Obama in the war on terrorism are trials for terrorists and taking the fight beyond Afghanistan to places like Pakistan and Yemen. This issue of whom we are at war with defines both of them.”

After September 11, Mr. Bush claimed virtually unlimited power as commander in chief to detain those he deemed a threat . But President Obama and his team have sought to demonstrate that the executive branch can wage war while also respecting limits imposed on presidential power by what they see as the rule of law.

In March 2009, the Obama legal team adopted a new position about who was detainable , one that showed greater deference to the international laws of war, including the Geneva Conventions, than Mr. Bush had. But what has not been known is that while the administration has stuck to that broad principle, it has been arguing over how to apply the body of law, which was developed for conventional armies, to a terrorist organization.

In February 2009, John D. Bates, a federal judge overseeing several cases involving detainees in Guantanamo Bay, Cuba, asked a provocative question: Did the new administration want to modify Mr. Bush’s position that the president could wield sweeping powers to imprison people without trial as wartime detainees?

The White House counsel, Gregory B. Craig, saw this as an important opportunity to demonstrate a break with Mr. Bush. Mr. Obama declared that he did not want to invoke unrestrained commander-in-chief powers in detention matters.

Mr. Obama’s Justice Department came back on March 13, 2009, with a more modest position than Mr. Bush’s. It told Judge Bates that the president could detain without trial only people who were part of Al Qaeda or its affiliates, or their “substantial” supporters. The department rooted that power in the authorization granted by Congress to use military force against the perpetrators of the September 11 attacks. And it acknowledged that the scope and limits of that power were defined by the laws of war, as translated to a conflict against terrorists.

But some criticized the notion that the United States could also consider mere supporters, arrested far away, to be just as detainable without trial as enemy fighters.

In September 2009, David Barron, a Harvard law professor and co-author of a law review critique of Bush administration policy, circulated a preliminary draft memorandum stating that while the Office of Legal Counsel had found no precedents justifying the detention of mere supporters of Al Qaeda who were picked up far away from enemy forces, it was not prepared to state any definitive conclusion.

“I think the change in tone has been important and has helped internationally,” said John B. Bellinger III, a top Bush era National Security Council and State Department lawyer. “But the change in law has been largely cosmetic. And of course there has been no change in outcome.”

But at a recent American Bar Association event, Harold Koh, a former human-rights official and Yale Law School dean who had been a leading critic of the Bush administration’s detainee policies and who became the State Department’s top lawyer in late June, argued that the administration’s changes ? including requiring strict adherence to anti-torture rules and ensuring that all detainees are being held pursuant to recognizable legal authorities ? have been meaningful. The United States, he said, can now defend its national-security policies as fully compliant with domestic and international law under “common and universal standards, not double standards.”

“We are not saying that we don’t have to fight battles,” he said. “We’re just saying that we should fight those battles within the framework of law.”


By CHARLIE SAVAGE


ANDRES LEIGHTON/ASSOCIATED PRESS
In defending Guantanamo, the Bush administration claimed broad powers, including detaining terrorism suspects without trials.