Yes, sad but true, if you are convicted of a DUI you may not be able to enter into Canada. This site has a step by step analysis of the crimes that will prevent admission into Canada. It further describes the steps necessary to file a certificate of rehabilitation or become a temporary resident. This process is theoretically the only way that a convict can be deemed admissible to Canada. Although, the simple fact is that admission to Canada will be based upon the discretion of the border guard.

The process of rehabilitation may be initiated when 5 years has passed since the conviction. If a person needs to be admitted to Canada prior to initiating or completing the rehabilitation process you may apply for a temporary resident permit.