Following Kelsen’s influential theory of law, the concept of validity has been used in the literature to refer to different properties of law (such as existence, membership, bindingness, and more), and so it is inherently ambiguous. More importantly, Kelsen’s equivalence between the existence and the validity of law prevents us from accounting satisfactorily for relevant aspects of our current legal practices, such as the phenomenon of “unlawful law.” This chapter addresses this ambiguity to argue that the most important function of (...) the concept of validity is constituting the complex ontological paradigm of modern law as an institutional-normative practice. In this sense, validity is an artificial ontological status that supervenes on that of the existence of legal norms, thus allowing law to regulate its own creation and creating the logical space for the occurrence of “unlawful law.” This function, I argue in the last part, is crucial to understanding the relationship between the ontological and epistemic dimensions of the objectivity of law. Given the necessary practice-independence of legal norms it is the epistemic accessibility of their creation that enables the law to fulfill its general action-guiding (and thus coordinating) function. (shrink)