Criminal legal codes draw clear lines between permissible and illegal conduct, and the criminal justice system counts on people knowing these lines and governing their conduct accordingly. This is the “ex ante” function of the law; lines are drawn, and because citizens fear punishments or believe in the moral validity of the legal codes they do not cross these lines. But do people in fact know the lines that legal codes draw? The fact that several states have adopted laws that deviate from other state laws enables a field experiment to address this question. Residents (N = 203) of states (Wisconsin, Texas, North Dakota, and South Dakota) that had adopted a minority position on some aspect of criminal law reported the relevant law of their state to be no different than did citizens of “majoritarian” states. Path analyses using structural equation modeling suggest that people make guesses about what their state law holds by extrapolating from their personal view of whether or not the act in question ought to be criminalized.