Canada, unlike the US, requires a license to run a cable TV channel, just like a license to have an over-the-air radio or TV station. Thus, their CRTC requires the cable channels to meet various requirements, including Canadian content laws (like the other broadcast media there---a minimum amount of Canadian-made content) and adhering to the channel's designated purpose. Thus, Teletoon can't pull a Cartoon Network and air live-action junk by the metric ton....
The US doesn't regulate cable TV the way it does broadcast TV, since cable's viewed as a privately-run enterprise you're intentionally paying for, and thus they have much greater freedom (hence the existence of South Park, Sopranos, Queer as Folk, etc. on cable) under the first amendment (freedom of speech and all)...
-B.