Unless I'm missing something, this this article did not give a single reason why it "will not be easy", aside from quoting the director of marijuana enforcement

Unless I'm missing something, this this article did not give a single reason why it "will not be easy", aside from quoting the director of marijuana enforcement in Colorado saying: "It’s going to be a lot harder to implement than you think". Otherwise, the article is just a description of the current landscape in the marijuana industry of Canada before legalization.