For retributivists, who believe that criminal sanctions should be used to punish only conduct that is blameworthy, the so-called mala prohibita offenses have always been a source of concern: When the conduct being criminalized is wrongful prior to and independent of its being illegal - as it is with presumptive mala in se offenses like murder and rape - the path to blameworthiness is relatively clear. But when the wrongfulness of the conduct depends on the very fact of its being illegal - as is said to be the case with presumptive mala prohibita offenses like fishing without a license and buying drugs without a prescription - the argument in favor of criminalization becomes more difficult to sustain. Unless one believes that law-breaking as such is morally wrongful, criminal penalties would seem hard to justify. That, in any event, is the standard liberal, retributivist view. As I shall argue, however, things are considerably more complicated than this account would suggest. No offense, at least in the real world, is wholly malum in se or wholly malum prohibitum. Rather, the concepts of malum in se and malum prohibitum should be understood as contrasting, scalar qualities that all criminal offenses, to one degree or another, possess. Under such a conception, an offense could be, say, 80 percent malum in se and 20 percent malum prohibitum, or 20 percent malum in se and 80 percent malum prohibitum. Thinking about malum in se and malum prohibitum in this way can help us make a more precise assessment of the moral content of criminal offenses, taking account of the various ways in which law and legal institutions inform their moral content, the reasons people obey such laws, and what it means to “obey” the law in the first place.