For greater clarity (as the Criminal Code of Canada often says) here is Canada's legal restriction on prosecuting people who have committed gross human rights abuses in other countries:

"No proceedings for an offence under any of sections 4 to 7 of this Act... may be commenced without the personal consent in writing of the Attorney General or Deputy Attorney General of Canada, and those proceedings may be conducted only by the Attorney General of Canada or counsel acting on their behalf." - Criminal Code of Canada

Canada's version of the Magnitsky Act is structured the same way. After all you don't want ordinary people, via Canada's justice system, bringing complaints against foreign human rights abusers with whom Canada is friendly.