Prime Minister Stephen Harper has an obligation to demand the repatriation of Omar Khadr because Canada was complicit in the torture of the Guantanamo Bay detainee, a lawyer for Khadr told Federal Court on Tuesday.

'I don't want to use the word "lie," but it was a demonstratively false statement that was made to the Canadian public.'— Nate Whitling, Omar Khadr's lawyer

While government lawyers argued Ottawa had nothing to do with any mistreatment, lawyer Nate Whitling said his client was subjected to the "frequent flyer program" — a process of constantly waking and moving a prisoner from cell to cell — to soften him up for interrogation by Canadian intelligence officials.

Despite knowing about the documented mistreatment, which several international bodies have condemned as torture, the Canadians went ahead and interrogated Khadr in the spring of 2004, court heard.

"This frequent flyer program was imposed to prepare [Khadr] for the Canadian interrogation; it was inflicted to get him to co-operate when he was interrogated by Canadians," Whitling told Justice James O'Reilly.

"Canada became implicated in the violation [of his rights] when it chose to proceed with the interview."

It was a "stretch" to argue the intelligence officer should have stayed away from Khadr in light of Canada's long-standing desire for access to him, said Crown lawyer Doreen Mueller.

"There is no connection between Canadian conduct and the harm [Khadr] complains of," Mueller told the court.

Khadr's lawyers are seeking a judicial review of Harper's decision to refuse to intervene in the Canadian's detention and prosecution at the American prison on Cuba, which has been criticized by numerous human rights groups and the United Nations.

The prime minister has repeatedly said he would not interfere. The Canadian government has also maintained the Americans reassured Ottawa of Khadr's humane treatment.

Khadr, now 22, is due to stand trial Jan. 26 for war crimes. The U.S. accuses him of throwing a hand grenade that killed an American army medic following a fierce four-hour firefight in Afghanistan in July 2002.

Khadr, who was 15 at the time, was badly wounded and near death when he was captured.

"We are obviously dealing with a child," Whitling said. "Torture, bad enough. Torture of a child, even worse."

Ottawa has pressed the Americans to ensure Khadr receives proper medical care, to take his age into account, and to allow him access to Canadian lawyers, Mueller told the court.

"Whatever assistance can be provided to him is constrained by the circumstances," she said.

Khadr's legal team has said Canadians don't need to ask themselves, at this point, whether Khadr is guilty. They just need to decide if he deserves the full protection of Canadian law.

On Tuesday, Whitling said Canada is obliged to demand repatriation, given the numerous violations of Khadr's rights under the Canadian Charter of Rights and Freedoms and international law and agreements, such as the UN Convention on the Rights of the Child.

He blasted Ottawa's repeated statements that the Americans had provided assurances of humane treatment for Khadr.

"I don't want to use the word 'lie,' but it was a demonstratively false statement that was made to the Canadian public."

Court heard that when authorities deemed Khadr to have been unco-operative with his Canadian interrogators, they kept him in solitary confinement in "refrigerator" conditions for a month.

Evidence of his mistreatment is "overwhelming" and amounts to cruel or unusual punishment, Whitling argued.

"When Canada is actually involved in those violations and has participated in them, then there can be a remedy," the lawyer said.

The remedy is for the Canadian government to demand his repatriation, he said.

But Mueller called Ottawa's approach reasonable, balanced and appropriate, and hence not open to review by the courts.

She also said Khadr's lawyers had now raised the same issues in four separate legal proceedings, which she said borders on "abuse of process."

O'Reilly reserved his decision.