NewRider is correct. I personally know of many musicians who have run into this. Sometimes, though, their opening act, or band or roadies aren't allowed in to Canada with them, which can make for an "interesting" show. (I won't say who the musician was, but I was witness to an unbelievable show at the Commodore in Vancouver; unbelievable in a bad way. The promoter of that show will not be bringing that musician back to Canada again.)