The federal opposition parties presented a united front in Ottawa in demanding the release of Omar Khadr.
The 21-year-old Canadian has been held at a U.S. military prison in Guantanamo Bay, Cuba for more than five years.
He is the only Westerner still being held at Guantanamo Bay.
The MPs believe that Khadr should be treated as a child soldier and want Conservative Prime Minister Stephen Harper to intervene in the case.
U.S. forces captured Khadr, who was 15 at the time, in Afghanistan in 2002. They have accused him of killing an Army sergeant with a hand grenade during a firefight.
Lt.-Cmdr. William Kuebler, Khadr's U.S. military lawyer, told Canada AM on Monday that they want Canada to "follow the lead of every other western country" and demand Khadr's repatriation to face justice here.
Canada has tried to give the U.S. the benefit of the doubt over conditions at Guantanamo and the legal process to be followed in prosecuting the detainees, he said.
"I think certain inaction can maybe be forgiven in the past. But it's become increasingly clear that this young Canadian's rights have been violated, and that he's going to be put on trial in a fundamentally unfair process unless the Canadian government acts soon to do something for him," Kuebler said.
The military commission process makes no distinction between child soldiers and adults, he said.
Khadr could be prosecuted in Canada or the United States in civilian courts, he said.
"There are also a number of non-prosecutorial options," such as the peace bonds option under section 810 of Canada's Criminal Code, he said.
CBA speaks out
Bernard Amyot, president of the Canadian Bar Association, told Canada AM that his group supports the closing of Guantanamo Bay.
"I believe that this facility is a grievous affront to the rule of law," he said from Montreal.
People detained there are not allowed the protection of due process of law, he said.
Omar Khadr has been "languishing" there for five years without even clear charges against him, he said.
The CBA and 34 other bar associations around the world are calling for Khadr's repatriation so he can be subject to a fair trial. "You don't have to say he's innocent or that he's guilty. We only say that he should get a fair trial," Amyot said.
