When Conventionalism Goes Too Far*

Abstract

Legal positivism used to be a lean theory. When it first entered the arena,challenging natural law theory, it was strikingly lean compared to itsopponent. It offered a thin concept of law, to replace the thick, value-ladenconcept developed in the natural law theory. And this was its strength. Thechampions of legal positivism argued convincingly that the conditions forthe existence of law had been made too thick. Natural law theory hadinjected the existence-question with moral considerations that were betterleft aside. In the words of John Austin, the existence of law is one thing,its merit or demerit is another (Austin 1996, 132).But these were the good old days. If you take a look at legal posi-tivism today, you will see that it is not such a lean theory anymore. Likean aging prizefighter, it has put on some weight over the years. In itsdevelopment after Herbert Hart, the concept of law offered by legalpositivism has been beefed up with a theory known as conventionalism.According to this theory, the existence of a legal order not only requiresthat legal officials obey its fundamental rule, the rule of recognition. Theexistence of law also requires that the fundamental rule is obeyed as aconvention. This means that the reasons for obeying the law must bebased on the expectation that others obey it. As Hart puts it: rules areconventional social practices if the general conformity of a group to