It will be argued, firstly, that there is a link between the legal validity of a norm and the rational justifiability of a requirement that judges should apply this norm, based on a normative conception of legal validity and the postulate that judges should act as rational persons; secondly, that rational justifiability of legal norms requires the construction of a legal system in a model of principles that differs from theories, e.g., of Kelsen, Hart, Dworkin and Alexy, which are not (...) fully adequate for a normative conception of law. (shrink)