Since 1952, because of a principle firmly anchored in the Canadian customs, the position of Governor General is occupied in alternation by English- and French-speaking Canadians. Can we claim that this tradition of alternation at the position of Governor General is now elevated with the statute of constitutional convention? First, the author establishes and analyzes the fundamentals characteristics of constitutional conventions, that is to say particularly the three conditions necessary to their existence: precedents, the feeling of obligation of the actors, and the presence of a reason. Then, the author applies these conditions of existence to the process of appointment of the Governor General of Canada, in order to determine if such a convention of alternation exists. More than a simple synthesis or an analysis, the present study also aims at criticising or at least a putting into question certain conclusions drawn by the Supreme Court of Canada in the two references relating to repatriation. It uses for basic screen the Canadian duality and a mythical character of the Canadian constitutional law: the Governor General.