A critical analysis of Kelsen’s theory leads to a broad concept of custom, which covers diverse types of customary norms, where the always required conviction of legal bindingness depends on different types of factual and normative reasons. In it we should include a strict concept of custom or legal usage, derogating custom, custom of general international law, custom that establishes an unwritten constitution, custom that establishes a new written constitution, judicial custom which creates a rule of precedent and custom newly (...) expressed in the judicial application of customary rules. The basic norm could be formulated as a constitutive norm: ‘If the norms created through the first historical constitution are effective, then the first historical constitution are valid.’ It is thus a customary constitutive rule that recognizes the first historical constitution as valid law. Norms which establish sources of law are constitutive rules, they can be customary norms or legislated norms, but if they are legislated, they have their validity recognized by, directly or indirectly, a constitutive customary norm. By using a broad concept of custom as a conventional practice, Hart implies that general recognition of a customary rule, together with the practice that accompanies it, are sufficient conditions of validity. A doctrine of recognition that is arrived at by means of criticism and a rational reconstruction of the doctrines of Kelsen and Hart regains the essential theses of the traditional recognition theory of Bierling and Engisch. (shrink)