Canada's Supreme Court gave a young Canadian prisoner held at Guantanamo Bay the chance to try to force Ottawa to release secret documents that could help show his innocence.
Lawyers for Omar Khadr, who is charged with murdering a US soldier in Afghanistan in a firefight when he was 15, will argue before the court next week that his detention violated international law.
Khadr, now 21, was taken prisoner in 2002. He said in an affidavit that U.S. interrogators repeatedly threatened to rape him and Canadian government officials told him they were powerless to do anything.
Defence lawyers say interrogations of Khadr in Guantanamo, carried out by members of the Canadian Security Intelligence Service, had violated Canada's charter of rights.
"That argument in turn requires a lot of analysis of whether or not what is going on in Guantanamo is contrary to international law," Khadr's lawyer Nathan Whitling told Reuters.
"If they (the judges) were to accept our arguments, that would be a basis for directing the Crown to produce the documents that we want to use as part of his defence."
Unlike other Western governments that have intervened in the cases of their citizens held in the U.S. prison on Cuba, Ottawa has not asked Washington to release Khadr, saying his case is serious.
The Supreme Court overruled the Justice Department, which had argued the judges were not in a position to make a decision about a case under US jurisdiction. A spokesman for Justice Minister Rob Nicholson declined to comment.