OTTAWA — The Supreme Court of Canada refused Thursday to hear arguments that Canadian troops in Afghanistan should apply the Charter of Rights in their dealings with prisoners.

That leaves it to the Military Police Complaints Commission to investigate whether foreign captives delivered to Afghan custody by Canadian troops are routinely tortured.

The high court gave no reasons for its decision to refuse the case, its usual practice in dealing with requests for hearings.

"The evidence was plain that Canadian-transferred detainees are being tortured," said Paul Champ, lawyer for Amnesty International Canada and the British Columbia Civil Liberties Association which brought the case.

"It is disappointing that the Supreme Court did not view this situation as warranting the attention of the highest court in the land."

The two groups have complained to the military police commission, which starts related hearings Monday.

Champ had hoped to argue before the high court that handing foreign prisoners to Afghan authorities without assurance they won't be tortured violates the charter.

The Federal Court of Canada, in a ruling essentially upheld by Thursday's decision, said the charter does not automatically apply and that captives must rely on international legal protections.

Amnesty International says Afghan prisoners have no effective way of enforcing such protections -- except through the Charter of Rights.

"Detainees held by the American army in Afghanistan are protected by the U.S. constitution, but individuals captured by Canadian Forces are not protected by the Canadian Charter of Rights and Freedoms," Champ said.

A spokeswoman for National Defence said the federal government is pleased with the Supreme Court's decision.

"The transfer of detainees to Afghan authorities is assessed on a case-by-case basis, in accordance with international law," said Melanie Villeneuve in an email response.

"Any decision to transfer made by the commander . . .takes into consideration the facts on the ground and input from other government departments including Correctional Services Canada and Foreign Affairs."

The fate of Afghan detainees has been the subject of intense and sometimes nasty debate in Parliament. The Harper government once accused opposition MPs who raised the issue of being more concerned about the fate of Taliban captives than Canadian troops.

Ottawa temporarily stopped the contentious transfers after published reports detailed claims of torture by foreign prisoners.

The government then announced in 2007 that it had signed a new deal with the Kabul regime allowing Canadian officials access to inspect prisons after captives were handed over.

But Amnesty International says there's little reason to believe much changed after that. The group has accused the federal government of stonewalling requests for detailed information on the number of detainees transferred and their subsequent fate.

At the very least, Amnesty says NATO forces should be jointly operating a prison site with Afghan officials to ensure human rights are upheld.

A study last year by the Afghanistan Independent Human Rights Commission -- a watchdog group supported by Ottawa -- found that fewer than 20 per cent of Afghan law-enforcement officials were aware it's illegal to torture crime suspects.

The commission found that "torture and cruel, inhumane and belittling behaviour" is widespread among Afghanistan's police and security agencies.