A bit late, the Toronto Star reports that Dion is a dual French/Canadian citizen, and intends to stay that way.
This actually might change my vote. The citizenship relationship ought to be a big deal. The Canadian government has an obligation to protect Canadian citizens, and I think Canadian citizens have correlative obligations of loyalty to the Canadian state. Same with French citizens to the French state (and the French are more serious about this than we are.) Since you can't have dual loyalties, we shouldn't permit dual citizenship.
It's bad enough that we have so many dual citizens in the ordinary population. To have one of them seek to be Prime Minister is too much.
Update: Andy suggests handing Dion over to the French authorities for treason against the Fifth Republic.