I'm way oversimplifying here:

Judges can only make decisions within their scope, the extent of the law, and on the evidence before them. They do have some jurisdiction within their court, like holding someone in contempt, but they can't convict when no charges have been laid.

Cops can be sued civilly, but since we're talking criminal law the charges would be determined by a crown. The problem is the whole criminal court process usually starts with cops arresting someone and presenting their reports, so good luck finding cops who will rat on a buddy. Or, a crown who wants to risk losing the cooperation of the police. I know one who moved to practice in another province after they went after an extremely corrupt detachment.

The CCLA has done a bunch of work taking up cases to hold cops accountable, but the whole judicial foundation isn't just cracked, it's crumbling. Ask any half decent crown, judge, or lawyer in private what they think of the police if you want to get stuck down a depressing rabbit hole.