Canadian courts grossly overreached when they ordered Ottawa to ask Washington to send a Canadian held at the Guantanamo Bay military prison back to Canada, a federal lawyer argued on Friday.

The government wants the Supreme Court of Canada to overturn lower court decisions that it had to ask the Obama administration to repatriate Omar Khadr, accused of killing a U.S. soldier during a firefight in Afghanistan.

The court heard oral arguments on Friday, and Khadr's legal team asked it to give a speedy ruling.

The case coincided with an announcement from U.S. Attorney General Eric Holder that Khadr was one of 10 Guantanamo inmates -- among 215 held there now -- against whom prosecutions would proceed.

Khadr's lawyers say Ottawa violated Khadr's rights in refusing to ask the United States to send him home. Canada said the courts could not dictate how it conducted foreign affairs.

"The courts have no more authority to order the government to request (Khadr's) repatriation than they have the power to order the government to recall the U.S. ambassador in protest or to order the government to amass our warships on the Baltic," federal lawyer Robert Frater told the court.

Two successive Canadian governments have declined to seek the repatriation of Khadr, now the last citizen of a western nation held at Guantanamo.

"We believe the U.S. legal process announced today should run its course," Conservative legislator Pierre Poilievre said on behalf of the government, noting that Khadr is charged with murder and with preparing roadside bombs in Afghanistan.

Khadr's case has not been helped by the fact that he is from a family with close ties to al Qaeda leader Osama bin Laden. His late father was an al Qaeda financier.

His lawyers say he was a child soldier, 15 years old when he was captured in 2002, and that the United States tortured him in Guantanamo by depriving him of sleep.

The Supreme Court last year found that Canada had taken part in an illegal process in interviewing Khadr in Guantanamo, given the sleep deprivation and the legal conditions there.

But Chief Justice Beverley McLachlin seemed to agree with Frater that conditions at Guantanamo had improved.

"Usually you'd expect a remedy to fix up, to remedy the very thing that's gone wrong. At this point there's no more recent evidence of torture or (Canadian) complicity," she told Khadr lawyer Nathan Whitling.

The situation surrounding Khadr was in flux in light of President Barack Obama's order that Guantanamo be closed and Holder's announcement that Khadr's case would proceed.

Washington did not say where the commissions would be held. If closes Guantanamo, they would likely move to U.S. soil.

Some of the Canadian justices seemed reluctant to create a new duty of the federal government to protect its people abroad given the lack of precedent in Canada or abroad.

"No national court has ever recognized such a duty to repatriate, to protect," Marie Deschamps told Whitling.