Gotta link for that? Not that it matters.
It seems he was definitely entitled to be Canadian, as far as Canada was concerned (Canada's loss, our gain).
But Cuber?
Which would probably have shot his daddy, should he have returned.
The same law which gives him American citizenship gives him Cuban citizenship as well.
You don’t understand international law. I will walk you through it. His father was a Cuban citizen. He entered the US on a Cuban passport in 1957. Since you seem not to be a history buff, I’ll add - two years before the Castro takeover.
His father continued to be a Cuban citizen, regardless of what later occurred in Cuba. He entered Canada on a Cuban passport. His citizenship was automatically passed on to his son. This is true of all fathers and their children all over the world.
There is no reason to believe that he would have been shot if he returned to Cuba, and it is irrelevant to his legal status as a Cuban citizen.