If it has been over five years since your conviction and / or termination of your sentence, you may apply for a pardon through the consulate. (Probation does not count as a sentence) If it has been ten years, then no pardon is necessary as they find that you have been rehabilitated enough. If it has been under five years, don't bother to apply, as no pardon will be considered. The DUI in Canada is in fact a felony charge, so they take it much more seriously then us in the states. I am not sure what the actual process is at the border but I think that you have to provide the proof of pardon from the magistrate when asked about your background.