The New York-based Center for Constitutional Rights and the Canadian Centre for International Justice say Canada's attorney general must launch a criminal investigation against George W. Bush.
The groups say Bush has violated a United Nations convention against torture by admitting to authorizing treatments ranging from assault to secret detention of prisoners.
They say because Canada has signed the UN treaty, it must act against the former president when he appears at a speaking engagement in Surrey, B.C., on Oct. 20.
Protesters unsuccessfully appealed for similar action against former U.S. vice president Dick Cheney when he visited Vancouver and Calgary earlier this week as part of a book tour.
Rallies were held in both cities as demonstrators denounced Cheney for alleged war crimes, but the only person arrested and charged with assault was a 51-year-old Vancouver protester.