I have no knowledge on what the practice is (or should be) in Canada, but here in the US it is not uncommon for judges to give "talks" to the general public or to law school classes. Inevitably at these talks (especially ones aimed at the general public), specific questions will arise. Usually the judge says something along the lines of "I can't comment on your specific case, but here is the law on this in general. You should consult a lawyer about your specific matter." I have never really given the issue much thought, but I suspect it has something to do with our moronic system of electing judges and those judges having to make sure the public know who they are.