No legal tradition in history has developed an account of law and legal validity that compares in significance to that of legal positivism. Its most celebrated theorist in the 20th century, Hans Kelsen, conceptualizes legal validity as produced and reproduced within a self-referential system of law. Yet, by focusing on law's self-referentiality, i.e., norms legitimating other norms, his theory fails to account for the complex interplay between positive and non-positive norms, and how this interplay is related to legal validity. More specifically, the positivist conception of law cannot account for how non-positive practices of legal adjudication produce and reproduce legal validity. To address this problem, I develop a "post-positivist" approach to legal validity grounded in non-positive norms of legal adjudication. I discuss three normative theories of legal adjudication that provide non-positive, practice-based accounts of legal validity. The three theories of adjudication I discuss are those of Ronald Dworkin, Jürgen Habermas, and Rainer Forst. In conclusion, a post-positivist approach to law means keeping positivism's notion of self-referential legal validity, but introducing other normative inputs that compete with it without negating it in an on-going fashion.