They should be turned over to law enforcement for prosecution.
Of course, there are acts that are crimes under church law, but not under civil law. (E.g., where minors are not involved.)
The state doesn't have the authority to remove a man from the priesthood; only to put him in prison. Similarly, the church (outside of the Vatican) doesn't have the authority to put a man in prison, but only to remove him from the priesthood. I think you and I probably both want it that way.