The Supreme Court of Canada wasted no time Thursday as it summarily rejected the federal government's bid to have former Guantanamo Bay prisoner Omar Khadr declared an adult offender.

The case — the third time the Khadr file has come before the high court — centred on whether the eight-year war-crimes sentence he got from a U.S. military commission in 2010 ought to be interpreted as a youth or adult sentence.

The federal government has argued the latter, saying Khadr actually received five concurrent eight-year terms, one for each of his five war crimes — a conclusion the nine justices rejected in a rare decision from the bench.

"The sentence is under the minimum for an adult sentence," Chief Justice Beverley McLachlin told the court after about 30 minutes of midday deliberations that immediately followed the end of the hearing.

"We are of the view that a proper interpretation of the relevant legislation does not permit Mr. Khadr's eight-year sentence to be treated as five distinct eight-year sentences to be served concurrently."

McLachlin ordered that appeal dismissed with costs, and confirmed the earlier order of the Alberta Court of Appeal that Khadr's sentence should be served in a provincial facility.

A spokesman for Public Safety Minister Steven Blaney said the government is disappointed with Thursday's Supreme Court decision and repeated the message it has maintained since Khadr was released on bail last week.

"At all times, we are focused on supporting the victims of crimes and ensuring the safety of Canadians. Omar Khadr has plead [sic] guilty to heinous crimes, including the murder of American Army medic Sgt. Christopher Speer," said Jeremy Laurin in an emailed statement. "Our thoughts and prayers remain with the family of Sgt. Christopher Speer during this difficult time."

Dennis Edney, the lawyer with whom the 28-year-old Khadr lives in Edmonton under strict bail conditions, said the swiftness of the ruling was a message to the Harper government for wasting taxpayer money on "persecuting my client."

Standing in the vast marble foyer of the country's highest court, Edney repeated the accusation that he first levelled at Prime Minister Stephen Harper last week.

"I come to the conclusion ... Mr. Harper is a bigot," he said. "Mr. Harper doesn't like Muslims and there's evidence to show that."

After almost 13 years in custody, the 28-year-old Khadr was released on bail last week while he appeals his U.S. conviction, which has drawn fierce criticism from legal and human rights experts.

Khadr was 15 when he threw the grenade that killed U.S. Sgt. Christopher Speer during a firefight in Afghanistan in July 2002.

Canada has extradition relations with some 83 countries, all of whom want assurances that an offender transferred here will serve their intended sentence, Department of Justice lawyer Sharlene Telles-Langdon argued during the hearing.

1 sentence or 5?

Several members of the panel challenged Telles-Langdon during her 50-minute oral argument before a packed courtroom.

"We can't slice and dice the eight years," said Justice Marshall Rothstein.

Compared with the mandatory adult sentence for first-degree murder, which is life behind bars with no parole eligibility for 25 years, "eight years for first-degree murder would be a youth sentence," Justice Andromache Karakastanis added.

Justice Rosalie Abella wondered aloud whether the U.S. government actually views Khadr's sentences as being concurrent. The only party that seems to take that view, Abella said, is the Canadian government.

Abella asked Telles-Langdon whether she considers eight years to be a youth sentence. Yes, the lawyer replied.

"Then, isn't that the end of the story?" Abella said.

Khadr's sentence is not open to interpretation, his lawyer Nate Whitling argued before the court. A concurrent sentence is without precedent in U.S. military procedure, and not supported in Canadian law, Whitling said.

"It is one sentence for eight years, and that is undisputed," he argued.

Khadr's lawyers say the Harper government is simply being vindictive as it pursues its tough-on-terror, tough-on-crime agenda prior to a fall election.

Court sided with Khadr in 2 previous cases

While the government concedes the sentence for the most serious charge — the murder of an American special forces soldier — can only be considered a youth sentence, it argued the other four, including attempted murder, must be viewed as adult sentences.

No provisions exist for an inmate to serve both youth and adult sentences at the same time, so Ottawa classified him as an adult offender when he transferred to Canada from Guantanamo Bay in September 2012 under an international treaty to serve out his punishment.

The federal government is bound by United Nations conventions that Canada has signed that protect the rights of the child and children in armed conflict, argued Fannie Lafontaine, a lawyer for Amnesty International, which was granted intervener status in the case.

The Canadian Civil Liberties Association, which has also intervened in the case, said Canada has consistently taken a heavy-handed approach towards Khadr.

The Supreme Court has taken up Khadr's case twice before, and sided with him both times.

In 2008, the court ruled Canadian officials had acted illegally by sharing intelligence information about him with his U.S. captors.

In 2010, the top court declared that Ottawa had violated Khadr's constitutional rights when Canadian agents interrogated him in Guantanamo Bay despite knowing he had been abused beforehand.