Canada must seek the immediate return of Toronto-born Guantánamo captive Omar Khadr rather than await the outcome of his U.S. military trial because American troops mistreated the alleged teen terrorist and Canadian officials knew about it, Canada's appeals court ruled Friday.

Omar Khadr at a hearing at the U.S. Military Commissions court for war crimes, at the US Naval Base, in Guantanamo Bay, Cuba in a court sketch. (Photograph by: Janet Hamlin, AFP/Getty Images) The Federal Court of Appeal's 2-1 ruling, issued in Ottawa, effectively instructs the Canadian government of Prime Minister Stephen Harper to intervene in the case before Khadr is tried by military commission.

His next hearing is Sept. 16 in the case that accuses the now 22-year-old Khadr of throwing a grenade that fatally wounded a U.S. Special Forces soldier in a firefight in Afghanistan in July 2002. Khadr was 15.

Harper has repeatedly said U.S. military justice should run its course, and his government said Friday that it was reviewing the ruling Friday afternoon.

"While Canada may have preferred to stand by and let the proceedings against Mr. Khadr in the United States run their course, the violation of his Charter rights by Canadian officials has removed that option,'' the majority wrote in the 53-page ruling and dissent.

Khadr could face life imprisonment if convicted under the war crimes tribunal system now being revised by the Obama administration.

His military lawyers have campaigned for his release, arguing he should have been treated as a vulnerable "child soldier'' when was captured near death after two bullets tore through his back. The Pentagon argues he was responsible for his actions.

The Canadian court ruled Friday that the Canadian officials were aware as far back as 2004 that Khadr was subjected to the military's "frequent flier'' sleep deprivation program to soften him up, and still interviewed the teen at the remote U.S. Navy base, then shared their findings with U.S. officials.

Testimony about the sleep deprivation program at Guantánamo's commissions showed U.S. troops systematically shifting captives between Camp Delta cells night and day ahead of scheduled interrogations.

"It is true that the United States is primarily responsible for Mr. Khadr's mistreatment,'' Justices John Maxwell Evans and Karen Sharlow ruled. "However, the purpose of the sleep deprivation mistreatment was to induce Mr. Khadr to talk, and Canadian officials knew that when they interviewed Mr. Khadr to obtain information for intelligence purposes. There can be no doubt that their conduct amounted to knowing participation in Mr. Khadr's mistreatment.''

In Washington, Canadian Embassy spokesman Jonathan Suavé said the Harper government was reviewing the "lengthy judgment with a strong dissenting opinion.''

"The Government of Canada will review it carefully,'' Suavé said. "It would be inappropriate to comment further on this matter.''

He noted that Canada's position on the Khadr case "remains unchanged. In fact, it is the same policy held by two previous governments.''

Canadian diplomats would continue to monitor the case, he said, as well as continue to hold "welfare visits'' with Khadr at Guantánamo.

Khadr's U.S. military lawyers have tried to avert a trial, arguing that he would become the first Westerner tried as a "child soldier'' in modern history -- a tactic that has garnered spotty sympathy for a member of what is known as Canada's "first family of terrorism.''

His father, an alleged al Qaeda militant and fundraiser, raised the child between Canada, Pakistan and Afghanistan until the Sept. 11, 2001, attacks, when the family scattered. The father died in a 2003 Pakistani forces raid on a suspected al Qaeda hideout.

Omar Khadr's older brother, Abdullah Khadr, is being held in Canada on a U.S. extradition warrant, accused of supplying weapons to al Qaeda. Another brother has acknowledged the family stayed with Osama bin Laden, and claimed he served as double agent for the CIA during a short stint at Guantánamo.

The younger Khadr allegedly threw a grenade in a July 2002 special forces assault on a suspect al Qaeda compound near Khost, Afghanistan, that fatally wounded Sgt. 1st Class Christopher Speer, 28, of Albuquerque, N.M.

Speer died of his wounds at a U.S. military hospital in Germany 11 days later. The Canadian was left blinded in one eye by his wounds, as was another U.S. soldier who has been expected to testify at the trial.

If Khadr is returned, the Canadian justices wrote in their majority opinion, "it will be for the attorney general to decide, in the exercise of his or her discretion, whether to institute criminal proceedings in Canada against Mr. Khadr.''

The dissenting justice, Marc Nadon, wrote that a lower court judge had overreacted by seeking Khadr's return because Canadian agents took part in the teen's Guantánamo interrogations.

"I cannot see the link between the inappropriateness of the interviews and the remedy of repatriation,'' he wrote, calling it "a remedy which is, in my view, totally disproportionate in the circumstances.''