Well I guess I have to scratch another thing off my list of differences between Canada and Japan. It seems Canada is not forcing non-citizens to get a kind of re-entry permit, called a Maple Leaf. Although I'm not sure if they are required to get one everytime they travel or is it a one time deal.
http://www.canoe.ca/NewsStand/OttawaSun/News/2003/12/09/281273.html