This paper aims to answer the following question: what is the understanding of the principle of sovereignty in the EU today, and how should this knowledge inform our actions tomorrow? It is demonstrated that from both doctrinal and practical points of view, it is impossible to determine conclusively what sovereignty or its preservation entails in the present European legal setting. The only point of clarity regarding the contemporary interpretation of sovereignty is that the principle should no longer be conceived in traditional and absolute terms – since this would be incompatible with the current European legal and political reality. Yet, while there seems to be an agreement on what sovereignty is not, there is no agreement, in either legal doctrine or practice, on what this principle actually is. It is argued that such a deeply contested nature of sovereignty puts in question not only the role and strength of this principle, but also the adequacy of its use as a legal parameter for determining the boundaries of the European integration process. It is thus concluded that in legal debates concerning the future of the EU, arguments relying on sovereignty should not be taken at face value. Rather, they should be approached with a critical eye and with full awareness of the disputed nature of the principle they rest upon.