I'd rather they only recommended punishment and advised the rest of us than if they were placed in charge of all punishment. There's too much risk in individual persecution if one group alone is in charge of themselves. But a group dedicated to establishing a code of conduct, and to understanding each other's magic, the rules for each (if at all possible) and recommended consequences for ignoring said code of conduct. We do need laws covering use of magic here, which is absolutely something other magic users can do for us. Then we could move forward from there as we would with any crime.