The disparity in how their law is enforced does not make it invalid on the northern border, any more than it does here in the U.S.A. does it? Let's face it, terrorists can come in from either way (referring the DHS involvement.) So, Cheech, you've never gotten a work permit, or visa when you've been there to work? Every time I went there for my former job, that was the first thing we did, because some of the guys that had been there other times before me had been checked, verifying that they DO check this stuff!