If you've been arrested:
Entry into Canada
If you are convicted of DUI you may be denied entrance into Canada. Customs and Immigration Officers are granted ultimate authority to permit and deny entrance in to Canada and routine screening upon entry into Canada includes the question, "Have you ever been convicted of a crime?"
In Canada, a DUI is a felony and an excludable offense under the Immigration Act. Anyone with a conviction in the United States that is treated as a felony or indictable offense in Canada is excludable from Canada. Other convictions that can make a person inadmissible into Canada include reckless driving, careless driving, misdemeanor drug possession, domestic assault, theft and shoplifting.
A criminal conviction does not automatically bar you from entry into Canada; however, it can make it difficult. Canadian law does not let you enter the country for at least five (5) years from the date of your conviction or completion of your probation. After the five-year waiting period you can apply for "criminal rehabilitation" by submitting an application to be deemed rehabilitated. Please note applications for rehabilitation can take over a year to process.
If there is any possibility that you will one day enter Canada, we recommend securing certified true copies of all court records relating to your conviction and sentence, including proof of fine payment as Canada typically requires them for review. Proof of sentences being completed is crucial.
Further information can be found at Canada's Citizenship and Immigration webpage: http://www.cic.gc.ca/english/visit/conviction.asp