Kelsen's two basic ideas on legal interpretation are, on the one hand, its characterization as a hybrid with both cognitive and volitional elements due to the partial indeterminacy of law, and, on the other, the relationship between legal interpretation and the structural properties of the legal system (dynamic principle). Kelsen's solution to the problem of irregular norms – the so-called "tacit alternative clause" – not only attracts accusations of decisionism but also seems to render the question of norm content and, therefore, legal interpretation, within his theory of law irrelevant. I will argue that a reconstruction of Kelsen's thesis which renders it less open to accusations of irrationalism is possible, starting from his initial intuition regarding legal interpretation. This reconstruction is based on two arguments: (i) the distinction between the validity of a norm and the fact that the act by which it is created is a correct interpretation of the higher norm, that is, a non-reductionist concept of validity; and (ii) a functional interpretation of the "determination" of the norm content between the different hierarchical levels of the legal system.