President Bush wants as much flexibility as possible to protect the United States from a repeat of the 9/11 terror attacks.
But does he have the authority to whisk a civilian in the US suspected of being an Al Qaeda sleeper agent into indefinite military detention without charge?
That's the question on Wednesday confronting all 10 judges of the Fourth US Circuit Court of Appeals in Richmond, Va., in a case examining the treatment of a graduate student from Qatar named Ali Saleh al-Marri.
The case raises one of the most significant unresolved constitutional questions in the war on terror, legal analysts say, and could set the stage for a landmark decision later at the US Supreme Court.
Mr. Marri has been held in an isolated wing of the naval brig in Charleston, S.C., for more than four years after being designated an enemy combatant by Mr. Bush in June 2003.
Government officials suspect Marri came to the US as an Al Qaeda sleeper agent to participate in a second wave of terror attacks after 9/11. Their suspicions are based in large part on information obtained through coercive interrogations conducted by intelligence officials overseas.
Coerced statements are not considered reliable enough to be admitted as evidence in an American courtroom. That means it could be difficult to win a conviction against Marri should the government attempt a terror-conspiracy prosecution within the criminal-justice system.
The Bush administration's alternative has been to simply declare the suspect an enemy combatant and order him detained in military custody, potentially for the rest of his life.
At issue before the appeals court is who can validly be held by US forces as an enemy combatant in the war on terror. The law of war permits the military to take war prisoners and hold them in detention facilities to prevent enemy combatants from rejoining the battle.
There is no doubt that someone captured while using an AK-47 on a battlefield in Afghanistan can legitimately be detained by the American military for the duration of the conflict.
What is less clear is whether the president can use his power as commander in chief to order similar open-ended military detentions of civilians in the US who are suspected of conspiring with Al Qaeda to commit future acts of terrorism in America.
The Bush administration argues that the battlefield in the global war on terror extends to every corner of the US itself. It does not just apply to those engaged in traditional combat on a raging battlefield. It also applies to those who secretly associate themselves with Al Qaeda and come to the US to conduct hostile, warlike acts on behalf of Al Qaeda.
Otherwise, government lawyers say in a brief, the president would be "without the authority to use the military force necessary to prevent individuals identically situated with Mohamed Atta and his cohorts from planning and executing another September 11 attack."
The president can use his military detention power against anyone in the US – including American citizens and foreign nationals who are in the US under a valid visa, government lawyers say. Once designated an enemy combatant and held in military custody, the detainee is stripped of most legal and constitutional protections and is held as if he had been taken prisoner on a traditional battlefield.
Lawyers for Marri say the Bush administration's use of military power against civilians in the US destroys the critical distinction between civilian and military jurisdiction.
"The government has sought here an unprecedented and wholesale erasure of that line," says Jonathan Hafetz in his brief to the court on behalf of Marri.
If endorsed by the judiciary, the administration's position would "allow a president, by the mere stroke of a pen, to avoid the criminal process in any case involving allegations of terrorism," writes Mr. Hafetz, who is also a lawyer at the Brennan Center for Justice at New York University School of Law in New York City.
"Our argument is that [Marri] is being held illegally. Either charge him or release him," says Hafetz in an interview. "They can't just lock him up."
In June, a Fourth Circuit panel decided 2 to 1 that Bush overstepped his constitutional authority in the Marri case. Now, the full appeals court is reviewing that decision.
In a brief, Assistant Solicitor General Eric Miller told the judges that the earlier appeals court ruling "poses an immediate and potentially grave threat to national security" by limiting the president's authority to capture and detain Al Qaeda agents.
Hafetz disputes the suggestion that national security is in peril. His client was "captured" by the military in a jail cell where he had been held within the criminal-justice system by the federal government for 18 months and was about to stand trial. Nothing prevents his return to the criminal-justice system, Hafetz says.