'Criminal' background

Hi, My dad wants to visit Canada for the purpose of attending my wedding. The problem is this, he is an ex political prisoner, in the North of Ireland. The details of what he was convicted with I dont wish to go into here, suffice to say it was not murder, manslaughter or rape. He was jailed for 7 years and served those in prison, and was released in 1984. From that date forth he had no dealings with any paramilitary organisation. Anyone who understands the situation in the North of Ireland in the late 1960's early 1970's will understand. Will he be admitted as a tourist or will he be deported if he lands in Canada. I have e-mailed various people but I have yet to get a reply. Any information at this moment in time will be greatly appriciated. Thank you all for your time