You may be inadmissible to Canada if you were convicted in Canada or outside Canada on grounds of criminality. This will either prevent an individual from entering Canada as a visitor, student, or worker, or from obtaining permanent residence or maintaining their PR status.
You will be found inadmissible if;
Conviction occurred outside Canada that, if committed in Canada, would constitute an offence punishable by a maximum term of imprisonment of at least ten years
Convicted in Canada of an offence punishable by a maximum term of imprisonment of at least ten years, or of an offence for which a term of imprisonment of more than six months was imposed
Human or International Rights Violations
Permanent residents and foreign nationals who have violated human or international rights outside of Canada are barred from entering the country.
Security Risk
A permanent resident or a foreign national seeking to enter Canada may be found inadmissible on security grounds if he or she is, among other things;
Engaged in an act of espionage against Canada or actions that are contrary to Canada’s interest
Engaged in or instigating the subversion of any government
Engaged in terrorism
A danger to the security of Canada.
Exemptions
Depending on the nature and facts pertaining to inadmissibility, a person found inadmissible (for example) by reason of serious criminality may be exempted and permitted to enter or remain in Canada if he receives a record suspension (a pardon), granted a conditional discharge or if he is acquitted of the offence in question.
With respect to offences committed outside Canada, the person will be exempt if he has been deemed to be rehabilitated or has demonstrated to the Minister of Immigration, Refugees and Citizenship that he is rehabilitated.
Organized Crime
Both permanent residents and foreign nationals may be found inadmissible for being members of an organized crime group.
Specifically, this section applies when a permanent resident or foreign national is a member of an organization that is believed on reasonable grounds to be or to have been engaged in activity that is part of a pattern of criminal activity OR applicant is engaged in activities such as people smuggling.