GUANTANAMO BAY, Cuba - U.S. military prosecutors are hoping for a smooth start to a landmark legal battle over Omar Khadr in their latest push to prosecute detainees in the war on terror.

But as the Canadian faced arraignment Monday, accused of throwing the grenade that killed an elite American soldier in Afghanistan in July 2002, it wasn't clear who would represent him.

Khadr, 20, fired his U.S. lawyers last week, saying he would only deal with his Canadian lawyers.

So the makeup of his legal team is likely to be the first order of business in a case American authorities hope will restore faith in the justice system they've devised for what they've called the "worst of the worst" terrorists.

If that's the goal, say critics, Khadr is an unusual choice among the 380 Guantanamo detainees, including 14 "high-value" prisoners transferred there from secret CIA prisons abroad who allegedly had a direct hand in the attacks on Sept. 11, 2001.

The military prison camp in southeast Cuba and the special tribunals created under President George W. Bush have been widely condemned by many countries, except Canada, as inhumane. Detainees languish in indefinite detention and could remain there even if they're acquitted at a trial.

But Khadr, who was only 15 years old when he was taken into custody, presents a special challenge as the first juvenile to face war crimes charges in decades.

To U.S. authorities, he's a dangerous killer who made his own decisions and must be held accountable for killing Sgt. 1st Class Christopher Speer, 28, who left behind a wife and two children.

"He could have surrendered," said John Bellinger, top legal adviser at the State Department. "He did make certain choices."

For activists, Khadr's as much of a victim as Speer and Sgt. Layne Morris, who was nearly blinded during the firefight.

"We have a kid who was dragged to meet al Qaeda leaders from the age of 10, sent to military training camps at age 15 and then out to the battlefield to be shot at," said Jennifer Daskal at Human Rights Watch.

"He hardly qualifies as the worst of the worst," said Daskal, adding his case should be moved to U.S. federal court.

Authorities insist international law permits them to prosecute Khadr as an enemy combatant without the rights afforded prisoners of war while others argue the United States has an obligation to rehabiliate child soldiers under a United Nations treaty it has ratified.

Meantime, some find it strange that Khadr is among only three prisoners to be formally charged since the military commission system was revamped last year after the U.S. Supreme Court ruled it was illegal.

"You have to wonder why it's Omar Khadr who may be the first to go on trial," said Jameel Jaffer, director of the national security project at the American Civil Liberties Union in New York.

To give others with links to the Sept. 11 attacks a hearing may expose some uncomfortable information about interrogation techniques employed by the CIA, he said.

"They don't want that information on the front of the New York Times."

This is the second go-round for Khadr, who attended pre-trail hearings in January 2006 before the Supreme Court nixed the tribunals.

He will have, said Bellinger, "the most extensive and robust" defence possible.

But it's unclear whether his Canadian lawyers, Dennis Edney and Nate Whitling, will be allowed to do more than act as so-called foreign attorney consultants as stipulated in the military commission rules.

Edney, who plans to challenge the process, has already ruled out a plea bargain for Khadr, saying the U.S. military would insist he serve another 30 years.

The Canadian Council on American-Islamic Relations has called on Ottawa to step in to ensure the Canadian lawyers have full participation.

"It seems the present government wants to forget that Omar Khadr exists," said spokesman Sameer Zuberi.

But Foreign Affairs spokesman Alain Cacchione said there will be no talks with U.S. authorities on the issue.

"The role Canadian lawyers can play abroad are subjected to the rules of military proceedings," he said.

Khadr is a member of a controversial Canadian family whose patriarch, Ahmen Said Khadr, moved them to Afghanistan and was close to terror chief Osama bin Laden. The elder Khadr was killed by Pakistani forces in October 2003.

"It's so easy to think of Omar as a kid from a terrorist family and not think of him as a kid from Ontario caught up in a lawless system," said U.S. lawyer Muneer Ahmad, who has represented him.