The country's top court refused to hear the application and dismissed Hassan Diab's appeal without costs on Thursday. As is usual in applications for leave to appeal, the court did not give reasons for its decision.
The decision means Diab can now be extradited to France.
French authorities allege 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 appealed 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 said France's reliance on secret information raises fundamental issues of constitutionality and procedural fairness.
'It is beyond devastating,' Diab writes
In a statement read by a supporter during a news conference Thursday afternoon, Diab wrote: "It is beyond devastating that the Supreme Court would allow my extradition for a crime that I did not commit, and based on a handwriting analysis report that was shown by world-renowned handwriting experts to be wholly unreliable, totally erroneous and biased.
"I vow to never give up, and I will always remain hopeful that I will eventually return to my home in Canada and be reunited with my wife and children," Diab wrote.
Diab's lawyer, Donald Bayne, called the top court's decision "profoundly disappointing."
"Unfortunately, in this case, we now have, in my view, a classic recipe for the wrongful conviction of a Canadian," Bayne said. "This could never meet Canadian constitutional standards for criminal trial, yet we're sending a Canadian to such a Kafkaesque trial, where he can't possible meet the standards of knowing the case against him and making and having a real and meaningful opportunity to answer that case."
Supporter incredulous case wasn't heard
Peter Gose, who taught at Carleton when Diab lectured there, was with a group of 20 protesters outside the courthouse when the decision was announced.
Gose said he was saddened by the result and said it was incredible Diab's appeal wasn't heard because his case has exposed serious problems with Canada's extradition laws.
The French Embassy in Canada noted the court decision in a statement Thursday and reiterated that "with regard to French law, Mr. Hassan Naïm Diab is presumed innocent."
"In France, he will be heard by an investigating judge in an open judicial inquiry regarding the attack that took place on Oct. 3, 1980, on Rue Copernic in Paris," the statement read.
But Gose said he and Diab's supporters are worried about what kind of trial Diab will have in France.
"They have anti-terrorism laws that allow them to treat as evidence unsourced and uncircumstanced intelligence," Gose said.
The Centre for Israel and Jewish Affairs commended the Supreme Court for upholding the lower courts' decisions.
Case weak against him, lawyers had argued
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.