Canada provides an interesting illustration of how far a system of government in practice may depart from the provisions of a legally valid constitution. Although in 1867 the British North America Act created a relatively centralized form of government, today, through changes wrought by geography, convention, and judicial decision, Canada's machinery of government is essentially federal in its operation. In other words, Canada has developed an “unwritten” constitution which goes far toward ensuring the independence of provincial governments in the exercise of exclusive powers. In one or two important respects, however, we find the federal character of Canadian government still somewhat in doubt. And it is by examining whether the existing system satisfies the essential requirements of federalism that the post-war developments in federal-provincial relations may be fruitfully analysed; by examining, that is to say, the extent to which these developments represent a movement towards or away from federalism.
Since World War II, Canada's constitutional system has been affected by three important changes: (1) federal-provincial financial arrangements have been radically revised; (2) the Supreme Court of Canada has been charged with the final interpretation of the constitution; and (3) the method of amending the constitution has been changed. It remains to record these developments in greater detail, and then to discuss their implications.