Ignorance of Law Is an Excuse – but Only for the Virtuous

It’s axiomatic that “ignorance of the law is no excuse.” My aim in this essay is to examine what the “mistake of law doctrine” reveals about the relationship between criminal law and morality in general and about the law’s understanding of moral responsibility in particular. The conventional understanding of the mistake of law doctrine rests on two premises, which are encapsulated in the Holmesian epigrams with which I’ve started this essay. The first is liberal positivism. As a descriptive claim, liberal positivism holds that the content of the law can be identified without reference to morality: one needn’t be a good man to perceive what’s lawful, Holmes tells us; one need only understand the consequences in store if one should choose to act badly. The nonnative side of liberal positivism urges us to see the independence of law from morality as a good thing. In a pluralistic society, the law should aspire to be comprehensible to persons of diverse moral views. What’s more, it should avoid embodying within itself a standard of culpability or blame that depends on an individual’s acceptance of any such view as orthodox; in a liberal society, even the bad man can be a good citizen so long as he lives up to society’s rules.