Starting in 1908 with a law based on welfare principles and finishing in 2003 with a law based on criminal law principles and proportionality, successive changes in Canada's youth justice legislation have provided additional structure in governing the key decisions involving youths. While criminal law in Canada, including youth justice laws, is a Federal responsibility, the provinces administer the law. Interestingly, there are very large differences in the manner in which the provinces administer the single (Federal) criminal law. Although most Canadians believe that the youth justice system is too lenient, the data show that many of the cases being processed through Canada's youth courts and many of the cases resulting in imprisonment for youth involve very minor offenses. Federal government concerns about the provincial overuse of the youth justice system and about the high rates of custodial sentences for minor offenses were important determinants of the shape of the most recent youth justice legislation - the Youth Criminal Justice Act (YCJA), which came into effect in 2003. For political reasons, these concerns were "balanced" with symbolically tough, but practically inconsequential, measures. It remains to be seen what the effects of the new law will be. (Published Abstract)