Unjust positive laws, then, are not valid law under the natural law view. As Cicero put it: “What of the many deadly, the many pestilential statutes which are imposed on peoples? These no more deserve to be called laws than the rules a band of robbers might pass in their assembly.” An “unjust” law’s supposed invalidity does not translate into a natural law defense that is recognized in court, however. Although a formal natural law defense is not recognized in court, judges may sometimes take natural law-oriented views into account when interpreting the law.
As compared with positivist judges, judges influenced by natural law ideas may be more likely to read constitutional provisions broadly in order to strike down positive laws they regard as unjust. They also may be more likely to let morality influence their interpretation of the law. Of course, neither judges nor natural law thinkers always agree about what is moral and immoral—a major difficulty for the natural law position. This difficulty allows legal positivists to claim that only by keeping legal and moral questions separate can we obtain stability and predictability in the law. To some, the debate between natural law and legal positivism may seem unreal. Not only is natural law unworkable, such people might say, but sometimes positive law does not mean much either.
For example, juries sometimes pay little attention to the legal rules that are supposed to guide their decisions, and prosecutors have discretion concerning whether to enforce criminal statutes. In some legal proceedings, moreover, the background, biases, and values of the judge—and not the positive law—determine the result. An old joke reminds us that justice sometimes is what the judge ate for breakfast.