They didn't want him coming to Quebec for fear that he might speak out for the Rose brothers and the other FLQ members who had kidnapped Pierre Laporte.
A packet of secret documents just released from dusty RCMP archives reveals that Mountie spies had a huge file on the French existentialist thinker.
The prime minister at the time was Pierre Elliott Trudeau, who loved philosophy, particularly that of France where he had studied.
The "Sartre" file fills two volumes totaling 234 pages, and dates back to 1952, clearly indicating the passion and determination of the RCMP to follow Sartre. There is enough in there for a doctoral thesis.
The Director of Security and Intelligence for the RCMP at the time was the famous RCMP Superintendent Raymond Parent, one of the greats of federal espionage in Quebec at this time.
Parent was the "controller" at this time of the famous Claude Morin, the leading bureaucrat in the Robert Bourassa government and later the eminence grise of the Parti Quebecois.
The documents reveal that Parent advised the Department of External Affairs in Ottawa in March 1971, that Sartre was going to Montreal, on his way to California, to attend the trial of activist Angela Davis.
Parent asked the Immigration Department to take steps to prevent Sartre from entering Canada, lest he stop off in Montreal and contact the FLQ.
Did the illustrious Claude Morin, know about the link?
With time all conspiracy theories are shown to be true, and eventually all the secrets become known.