You are mixing up different points of law. Yes, the Canadian police does not have jurisdiction to prosecute for crimes committed abroad (somewhat, but let’s not get into that complex legal minefield here), but as an employee, you would have signed a contract with a clause to allow the employer to terminate your employment if you did anything illegal or brought the employer into disrepute. Government employees would normally have tighter regulations in this regard.
So, if you got involved in illegal rioting abroad while being an active reservist and made international news, at a minimum you can expect to have your reservists status terminated. Failure of the armed forces to take any action is effectively condoning your actions through their own inaction, which opens them up to accusations of your rioting being approved if not outright ordered by the chain of command, and they would know that, which is why if such extracurricular activities were not sponsored, governments tend to throw the book and then some at the offenders to prove beyond doubt that they weren’t involved.