"Section 19(2)(a.1) of the Immigration Act of Canada states that persons convicted of an offence outside of Canada, that would be an offence under Canadian law, cannot be admitted to Canada. Criminally inadmissable persons can, however, apply for a special permission to enter Canada. This special permission is expressed by a Minister's Permit."
Any person living in the United States who possesses a criminal record and wishes to travel to Canada will need a Ministers Permit. This is valid up to one year. One may also apply for a Rehabilitation. This document is a permanent approval, and allows hassle free border crossing into Canada.
The Canadian Government will look at each application individually. They will consider the following factors:
1) Nature of conviction
2) Date of last conviction
3) Sentencing
4) Reasons for travel
A Ministers Permit may take up to 6 months for processing. A personal interview may be required at the port of entry nearest the applicant's residence.
Rehabilitation allows lifetime access into Canada. This document never needs to be renewed. A Ministers Permit and Rehabilitation does not permit one to work in Canada. These approvals allow visitation for a period up to 6 months at a time.
Interestingly enough, President Bush had to file for these papers as he has a DUI conviction. He can cross the border until 2004 according to his paper work."
By amricca (2007)
Check out the following website for the latest information:
http://www.cic.gc.ca/english/visit/faq-inadmissibility.asp
http://www.cic.gc.ca/english/information/inadmissibility/conviction.asp
http://www.cic.gc.ca/english/information/inadmissibility/who.asp