You may be a criminal without even knowing it. Centuries ago, there were only nine felonies under English Common Law. The common law dealt with behavior that is widely understood to be culpable — murder, theft, rape, etc. — but in today's state legislatures and in Congress, innocuous behavior is too often criminalized. In Michigan, a person can be convicted of a crime for betting in an office March Madness pool, or mocking a person who refuses to duel. Accompanying this over-criminalization is the failure of legislatures to define the intent necessary for a prosecutor to prove a crime has...