The court's ruling stems from an August 2006 incident in which a tree maintained by the City of Westmount fell and killed Gabriel Anthony Rossy, who was in his automobile.
His family sued the city for failing to maintain the tree, but a Superior Court judge dismissed the action, saying it was a matter that should be dealt with through the province's Automobile Insurance Act.
The Quebec Court of Appeal overturned that ruling and found that the car had nothing to do with Rossy's death.
It ruled it was simply something he was sitting in when he died.
In its 7-0 decision, the Supreme Court restored the lower court ruling and dismissed the lawsuit against Westmount.