Territorial Sovereignty has been treated as a presupposition without the perspective of history in the study of international relations. This paper aims at tracing back the relationship between authority and space in the Middle Ages, finding it was defined by feudatory¡¦s fealty and alliance rather than by boundaries. Therefore, authority space in the Middle Ages could overlap and coexist above one land. On the contrary, modern national boundary excludes other authorities from its territory; territory serves as a container to reify power in the modern time. Besides, this paper shows that processes of re-scaling of authority space, which include sub-national spatial scales of global cities and supra-national spatial scales of the European Union, constitute the current round of globalization. This development of overlapping authority spaces could be conceived as a sign of arrival of Neo-Medievalism.