It's a matter of reasonable effort. How can a company determine that a given email destination is Canadian? It really can't. So Canada's laws are affecting the whole world as companies have to either give up on things that people likely actually want (security bulletins) or scramble to form opt-in databases on worldwide recipients just because of Canada.
No, it's a matter of being a decent business partner, regardless of the country you do business in, as a company with moral standing you give the options of opt-in and opt-out.
In the EU it's been that way for several years and it caused no grief to any company that does value it's customers.
Many of the companies scrambling already have double-opt-in to get in and very thorough opt-out options (Reply, click in any one of three places, idle detection auto-culling, etc.). So why are they scrambling? Because being a decent business partner is not good enough for the law. And again, the people it won't affect are the Canadian Pharma spammers (as an excellent example, since I'm staring at one's email in my spam box right now) who operate outside the law and know it and don't care. Decent business partners screwed. Actual spam still there. Can of worms with people affected by one country. Part of the reason there are so many US-Only sellers. They won't sell anything to the rest of the world because there are so many countries that would suddenly try to extradite the owners of the site for eyeball removal or something*.
(*Eyeball removal is not common, but a rat's nest of laws, many of which contradict each other, is out there, making the cost of allowing people from other countries much more expensive than the margin allows for.)