EDMONTON -- Alberta's top court says it needs time to decide where Omar Khadr should serve his sentence for war crimes.

The Appeal Court is considering whether the former Guantanamo Bay detainee should be serving a youth or adult sentence and, if it's a youth sentence, should he be transferred from a federal prison to a provincial jail.

Khadr's lawyers argue he was sentenced as a youth and should be moved to provincial custody. The federal government argues he is serving an adult sentence and should remain in the federal system.

Two of the three judges on the panel said Wednesday that the law suggests Khadr was likely sentenced as a youth. But after nearly three hours of questions aimed mostly at a federal government lawyer, Chief Justice Catherine Fraser said the court's decision on the "very interesting issue" would come at a later date.

The Toronto-born Khadr pleaded guilty in 2010 to five war crimes, including murder, for killing a U.S. soldier in Afghanistan when he was 15. He was accused of throwing a grenade that killed Sgt. Christopher Speer, during a vicious battle at an Afghan compound in July 2002.

A U.S. military commission sentenced Khadr to eight years beyond the dozen he'd already spent in Guantanamo Bay. It made no distinction between youth and adult punishment or between consecutive and concurrent sentences.

In 2012, he was transferred to Canada and corrections authorities took him into adult custody.

He was initially kept at a maximum security prison in eastern Ontario. He was moved to Edmonton's maximum security prison and, a few months ago, was reclassified as medium security and transferred to Bowden Institution in central Alberta.

Last fall, he lost his bid for a transfer to a provincial jail for less violent offenders.

Court of Queen's Bench Associate Chief Justice John Rooke sided with the federal government, ruling Khadr may have been sentenced as a youth for murder but, on the other offences, was sentenced as an adult. He said Khadr's placement in a federal prison was lawful.

Khadr's side appealed.

He is also appealing his war crimes convictions. In that case, his lawyers argue the offences have no validity in either international or American law. Khadr claims he felt hopeless and pleaded guilty to avoid more years of torture and abuse in Guantanamo Bay.

The 27-year-old sat straight in the prisoner's box as dozens of supporters, some wearing orange ribbons, packed the courtroom Wednesday. Others were sent to an overflow courtroom set up next door to watch the proceedings on a monitor.

One of his lawyers, Nathan Whitling, told the court that Khadr should be released entirely from custody because his detention is unlawful. But, because that's not a "practical outcome," Whitling said provincial jail is the next best thing.

Bruce Hughson, the lawyer representing the federal government and Correctional Service of Canada, said when Canada took Khadr back, it agreed he would serve the eight years. And Canada is not allowed to review or modify the sentence, he said.

The chief justice said she agreed with the argument that the eight-year sentence could be a youth sentence. A murder charge in Canada's adult court would net a life term and youth and adult sentences cannot be served at the same time, Fraser said.

Justice Jack Watson said classifying Khadr's sentence as a youth sentence wouldn't change the length of the term.

The court didn't give a timeline for when it would hand down its ruling.