Depends. Does the Catholic groom or bride have a dispensation? If not, then the Catholic Justice of the Peace is an accomplice to the Catholic bride or groom’s sin and is sinning himself. Of course, I’m not sure if the JP is always aware of the religious affiliation of those seeking civil marriage. If he is unaware, then he is not an accomplice. I know if they don’t ask for that information, he has no right to ask for it because it violates one’s privacy.