04/27/2013 01:59 EDT | Updated 06/27/2013 05:12 EDT

Omar Khadr Will Appeal Terrorism Convictions, Lawyer Says

Omar Khadr will appeal his plea-bargained guilty plea and war crimes convictions in a U.S. civilian federal court, his Canadian lawyer has told CBC News.

Khadr, 26, has been held in maximum-security Millhaven Institution in Bath, Ont., since he was returned to Canada last September from Guantanamo Bay where he had been held for a decade.

The transfer was as a result of a plea deal reached with prosecutors in October 2010 when Khadr pleaded guilty to and was convicted of killing Sgt. 1st Class Christopher Speer – an American medic in the U.S. army – with a hand grenade in Afghanistan in 2002, when he was 15.

As part of the plea, Khadr also confessed before a military commission in Guantanamo Bay to five war crimes, including murder in violation of the law of war, attempted murder in violation of the law of war, conspiracy, providing material support for terrorism, and spying.

He also agreed not to be part of any lawsuit against the United States or to enter the country after his transfer to Canadian custody or to profit from any publication of his story.

- Key events in the Omar Khadr case

Khadr's charges, according to his lawyer, Dennis Edney, "are not recognized international law–of–war offences. We questioned the validity of the charges before the Military Commission Process."

The charge of murder in violation of the law of war is "particularly offensive and not recognized by any legal observers outside the commission process," Edney said.

"We expect the military tribunal convictions will be overturned considering the present state of the law and ultimately putting to rest the Harper government's characterization of Omar Khadr as a war criminal and a terrorist."

Question of international law

The U.S. Office of the Chief Defense Counsel has named lawyer Sam Morison to lead an appellate team of attorneys to represent Khadr.

"My job at this point is to advise [Khadr] of his post-trial rights and then proceed as he directs," Morison told CBC News in a telephone interview on Saturday.

Khadr's legal team believes that "none of the charges" to which he pleaded guilty are war crimes under international law.

"If we are correct about that then the convictions are invalid and would have to be vacated," Morison said.

Khadr's U.S. lawyer expects the U.S. Court of Appeals for the District of Columbia Circuit to overturn Khadr's convictions based on two previous rulings where two of Osama bin Laden's aides who were convicted at Guantanamo later saw their terrorism convictions overturned.

Khadr agreed to a sentence of eight years, with no credit for time served, with the first year spent in U.S. custody.

Under Canadian law, Khadr will be eligible for a parole hearing in July, at which point he will have served one-third of his sentence.

Response from Ottawa

Julie Carmichael, a spokesperson for Public Safety Minister Vic Toews, issued a statement to CBC News on Saturday afternoon regarding Khadr's decision to appeal.

"Omar Khadr is a convicted terrorist," the statement said. "Decisions related to his future will be made by the Parole Board of Canada."

- Key questions on the future of Omar Khadr

According to Morison, if Khadr is successful in his appeal, the Canadian government would have to release him from jail immediately.

"There would be no basis for Canada, for the Canadian government, to take a position on this one way or the other."

"Under the provisions of an international transfer agreement, the receiving state … takes responsibility for executing the judgment. But they have no role in determining the validity of the underlying conviction. That's a matter for the U.S. courts," Morison said.

"If the U.S. courts were to throw out Khadr's convictions, there would no longer be any legal basis to hold him in prison."