Paradiplomacy is international relations conducted by subnational or regional governments on their own, with a view to promoting their own interests. With globalisation, non-state regions play an increasingly influential international role. Regions, federal states, provinces and cities seek their way to promote trade, investments, cooperation and partnership in a long list of subjects and account for a significant part of today’s cross-borders contacts. This trend raises new interesting questions concerning Public International Law and opens a debate on the future of the state system that has provided the grounds for the international political order in the last centuries.