OTTAWA - It's time for the Harper government to seek the return of Omar Khadr from a U.S. military prison now that an appeals court has upheld an order to bring him home, say supporters and opposition MPs.

In a 2-1 judgment Friday, the Federal Court of Appeal dismissed a challenge by the government, which has consistently refused to ask that the Toronto-born prisoner be sent back to Canada.

Khadr, 22, is being held by the Americans at Guantanamo Bay, Cuba, for allegedly throwing a grenade that killed a U.S. soldier in Afghanistan seven years ago.

Dennis Edney, one of Khadr's lawyers, said the courts have spoken clearly: "It's time for this Canadian government to follow the rule of law."

Prime Minister Stephen Harper noted that the ruling was a "split decision," but refused to speculate whether the government will appeal to the Supreme Court of Canada.

"The Department of Justice will be examining that decision and obviously I won't be commenting until we see their analysis and their recommendations," he said in Chelsea, Que.

Previously, Harper has said Canada would wait and see what the administration of U.S. President Barack Obama does in Khadr's case.

Liberal foreign affairs critic Bob Rae said it's no longer acceptable for Khadr to remain at the prison.

"I think the government's case has been blown out of the water."

Paul Dewar, the NDP foreign affairs critic, said the government has "no place left to hide now."

"There's no response left other than to do the right thing and bring him home."

Documents show Khadr's captors threatened him with rape, kept him isolated and deprived him of sleep by moving him from cell to cell.

The Federal Court of Canada ruled in April that the Conservative government must ask the United States to return Khadr "as soon as practicable."

It said Canada's refusal to request his repatriation offends fundamental justice and violates Khadr's constitutional rights to life, liberty and security of the person.

The appeal court rejected the government's bid to overturn the decision, saying the conduct of Canadian officials who interviewed Khadr at Guantanamo amounted to "knowing participation" in his mistreatment.

U.S. military court proceedings initiated against Khadr four years ago remain up in the air.

Successive governments, both Liberal and Conservative, have refrained from intervening in the Khadr case. The Tories have rejected a growing chorus of calls to deal with him on Canadian soil.

Canadian officials questioned Khadr at Guantanamo and shared the results of their interrogations with the Americans.

The appeal court said the principles of fundamental justice do not permit the questioning of a prisoner to obtain information after he has been subjected to cruel and abusive treatment to induce him to talk.

"Canada cannot avoid responsibility for its participation in the process at the Guantanamo Bay prison by relying on the fact that Mr. Khadr was mistreated by officials of the United States, because Canadian officials knew of the abuse when they conducted the interviews, and sought to take advantage of it," the majority ruling said.

Public release of a video in which a teenaged Khadr cries for his mother sparked an international uproar last year.

In his dissenting opinion, Justice Marc Nadon said the fact Canadian officials interviewed Khadr cannot amount to cruel and unusual treatment, even if they were aware that he had been denied sleep.

"Mere knowledge of Mr. Khadr's mistreatment cannot be equated with participation in such mistreatment."

In May 2008, the Supreme Court ruled Canada had taken part in a foreign process that breached its international human rights obligations.

The Khadr family has gained notoriety for apparent longstanding ties to al-Qaida leader Osama bin Laden.

Omar's father, Ahmed Said Khadr, was a purported extremist and financier for bin Laden's terror network. He was killed by Pakistani forces six years ago.

A brother, Abdul Karim, was left a paraplegic from wounds suffered in the shootout.