This contribution analyses the development of the doctrine of fundamental rights of states in German international legal doctrine. It shows how the doctrine, despite its natural law origins, was able to adapt and flourish in a more positivist environment in the late nineteenth and early twentieth century. It was highly malleable with respect to the uses to which it was put. Accordingly, it was relied on in order to support National Socialist conceptions of international law as well as to connect with a return to natural law after the Second World War. With a turn to more pragmatist approaches in German scholarship since the middle of the twentieth century, the doctrine seemed to have faded away. However, this contribution argues that it has witnessed a somewhat unexpected comeback. Driven by some functional and constructive analogies with parts of the constitutionalisation literature, it is possible to see traces of the doctrine re-emerging. In this respect, it may even be said to resemble parts of the recent case law of the German Federal Constitutional Court, which has put a strong emphasis on sovereignty and self-determination as limits of international and European integration.