French authorities allege Hassan Diab was a member of the Popular Front for the Liberation of Palestine. They also claim he took part in the 1980 bombing of a Paris synagogue that killed four people and injured more than 40 others.
Diab, a Canadian citizen, has repeatedly denied the allegations. He and his legal team are appealing an extradition order over what they describe as crucial questions about the use of untested intelligence in a criminal prosecution.
In arguments filed with the Supreme Court, lawyers for the sociology instructor say France's reliance on secret information raises fundamental issues of constitutionality and procedural fairness.
In 2011, an Ontario judge ordered Diab extradited even though he said the case against him was weak. Diab has been living under house arrest ever since.
The lower court's decision was upheld by Ontario's Court of Appeal and the federal Justice Minister.
Donald Pratt, who went to graduate school with Diab in the 1980s and is a member of Diab's support committee, said he's critical of Canada's extradition law, which he said allows evidence even the judge called problematic.
"If this case is not challenged successfully in the Canadian system, this will set a new precedent — a dangerous new low on what's acceptable to extradite," Pratt said.
French authorities say Diab's handwriting resembles five words written by a suspect. Diab's lawyers had five handwriting experts testify that the analysis is flawed.
Pratt said his friend's case is highly politicized because the bombing is unsolved.
"Clearly you know Hassan's background as an Arab and the whole climate around terrorism is clearly a factor in this," Pratt said.
Under Canada's extradition law, Diab was incarcerated Wednesday in advance of the high court's decision. Pratt said Diab is worried about his pregnant wife and his young daughter.
"Of course going in with the uncertainty if he's ever going to come out this time is weighing heavily on him," Pratt said.