International law states that another country's "political" laws and tax laws are non-extradictable. So draft dodging is a non extradictable offence.Crimes covered in the treaty are defined and extradition on crimes associated to your personal beliefs is tricky. These draft dodgers did not get charged for any criminal acts recognized by the treaty. They might even suggest their lives are in danger do to an arbitrary federal run draft lottery. I don't know details but I can see it would be complicated.
FYI: The details of the treaty are here - https://www.treaty-accord.gc.ca/text-texte.aspx?id=101323