According to deterrence justifications of legal punishment, legal punishment is justified at least in part because it deters offenses. These justifications rely on important empirical assumptions, e.g., that non-punitive enforcement can't deter or that it can't deter enough. I’ll challenge these assumptions and argue that extant deterrence justifications of legal punishment fail. In the process, I examine contemporary deterrence research and argue that it provides no support for these justifications.