Well, the rules for Canada are given here: http://www.cadomains.ca/rules.htm The gist of it is, to register a company's domain name to end in .ca you have to have a "strong" Canadian connection (certain percentage of employees, etc., being Canadian citizens or Permanent Residents).

The trademark rule is interesting. You can register a domain name using only the exact wording of the trademark if that trademark is registered in Canada. So (for example) yahoo.ca gives me a Canadian version of yahoo.com, even though the guys at Yahoo! most likely don't live here.