Former Guantanamo Bay prisoner Omar Khadr will be appealing his five war crimes convictions.

Lawyers for the 27-year-old Canadian will argue the U.S. military commission that heard his case had no legal authority to try him or accept his guilty pleas related to the death of a U.S. soldier during a battle at an Afghan compound in 2002.

They will also argue that what he's accused of doing as a 15-year-old in Afghanistan was not a war crime under U.S. or international law.

The appeal is to be filed in the U.S. Court of Military Commission Review in Washington, D.C.

Toronto-born Khadr was sentenced to eight years in prison after pleading guilty to war crime offences, including murder, providing material support for terrorism and spying. He was returned to Canada in September 2012 to serve out his sentence and is currently in prison in Edmonton.

Khadr's lawyers argue that the soldier's death occurred during the heat of battle and that Khadr's actions do not qualify as war crimes under international law.

But the military says Khadr was not in uniform and was therefore what's called an unprivileged combatant.

His lawyers say Khadr pleaded guilty to get out of Guantanamo.