OTTAWA, Ontario—A judge ruled Monday that a Canadian man can be extradited to France in connection with a 1980 Paris synagogue bombing that killed four people.

The decision by Ontario Superior Court Justice Robert Maranger means Hassan Diab is a step closer to being tried for murder in the 31-year-old terrorism case.

Canadian police arrested Diab, a 57-year-old Canadian of Lebanese descent, in 2008 in response to a request from France, where he is wanted on charges of murder, attempted murder and destruction of property in the Oct. 3, 1980, bombing.

The bomb, hidden in the saddlebags of a parked motorcycle, exploded outside a Parisian synagogue during a Sabbath service, killing three French men and one Israeli woman. About 200,000 people later marched through the streets of Paris to protest the attack.

Maranger concluded that France had presented “a weak case” that makes the prospect of conviction “unlikely.” But he said Diab must be surrendered under the terms of Canada’s extradition law.

Stamps in Diab’s 1980 passport indicated he was not in France at the time of the bombing.

But his handwriting allegedly appears on a hotel registration card—evidence his lawyers have vigorously disputed.

Still, Diab’s supporters were not hopeful in advance of the court ruling.

“The judge has signaled that he is likely to rule in favor of committal because Canada’s extradition law does not allow him to discard the handwriting  evidence,” the Diab support committee said in a statement.

Diab’s removal from Canada could still take years as he can appeal. Canadian Justice Minister Rob Nicholson will have the final say.

The Popular Front for the Liberation of Palestine-Special Operations was blamed for the bombing at the time. The investigation was reopened after Diab’s name turned up on a list of former members of a Palestinian extremist group obtained by German intelligence officials.

Diab denies any role in the deadly attack, saying it is a case of mistaken identity. Diab had been a part-time sociology professor at both Carleton University and the University of Ottawa before his arrest.