This is part of the National Defence Act, part of the Queen's Regulations and Orders, and also part of our internal policy, which we call the Defence Administrative Orders and Directives on enrolment. It clearly states that Canadian citizens are being given the priority, and that permanent residents, those non-Canadian citizens with permanent resident status, can be enrolled if there is a special need, if they provide service that satisfies a special need, and whose enrolment, in the opinion of the commander of the Canadian Forces recruiting group, would not prejudice the national interest. This is only when those two factors are met.
On March 19th, 2013. See this statement in context.