"It depends. If you have been convicted of driving under the influence, you are criminally inadmissible to Canada. However, you may be eligible for individual or deemed rehabilitation, depending on how much time has passed. Under some circumstances, you may also be offered a fee-exempt temporary resident permit for one visit to Canada under CIC's new policy on criminal inadmissibility."

http://www.cic.gc.ca/english/helpcentre/answer.asp?qnum=152&top=8