The Canadians know how to write a law.  Here we have laws for phone marketing and we have laws for fax marketing and we have laws for email marketing.  The Canadian way does not encompass all forms of marketing, but it should and it is a good start.  These days e-mail is almost rendered useless by SPAM.
Here is how the Canadians do it, via ITBusinessEdge online:
"The Canadian government passed CASL in December 2010 to establish a regulatory framework for permission-based marketing, including email marketing, social media marketing, text, and other electronic messaging. This framework will protect electronic commerce in Canada, deter damaging and deceptive forms of spam, such as identity theft, phishing and spyware, and drive out spammers."

Enforcement is the defining issue.  We shall see.