Term employed by Hart for a rule determining which body has the authority to create law in a society. Although Hart believed that such a rule was needed to distinguish law from the arbitrary dictates of power, it is arguably neither necessary nor possible for a rule to perform this feat. Not necessary because a habit or convention, according to which enough people expect enough other people to allow authority to some sovereign body, and are then prepared to follow along, will perform the same role. And not possible because in a state in which no body has the authority to issue law, no body will have the authority to create a rule delegating that authority either. See also positivism (legal), voluntarism.