Implying rights and obligations that are not explicitly set forth in a treaty is not a technique of treaty interpretation explicitly recognized in the Vienna Convention. But the practice of treaty interpretation supplies numerous examples of interpretively implied consequences of express treaty commitments. This chapter focuses on some of the best-known examples of treaty interpretation based on necessary implications ranging from the theory of implied powers of international organizations to the doctrine of positive obligations in international human rights law. Building on philosopher Robert Brandom’s theory of inferentialism, it argues that what is presented as necessary implications in treaty interpretation are discursively articulated inferential consequences of formal commitments undertaken under the treaty.