Canada, yes. you will be denied entry unless you obtain a special diplomatic waiver. It's a nuisance even after you get the waiver. Every time he enters, that crewmember has to go into a room and get quizzed by the customs heavies, while the rest of us stand around and wish we could go to the hotel already

Some airlines that go into Canada will not hire anyone with DUI (or any other conviction) for this reason...if they train the person and then find out that Canada will not issue him a waiver, everybody's SOL.