I was reading around Christmas last year that b/c of the new, extensive US databases, Canada's denying entry to more and more people. These were more recent arrests, but the article was talking about people who'd be cited for pot in the '70s being turned back, even if they're previously been able to get in, no problem.

Canada seriously needs to reevaluate what resources (and how crappy they are on this end) they're using to allow entry, but with Stephen Harper around - don't hold your breath!