In view of the proliferation of international organizations in the past century, it has become trite to claim that, especially through the creation of regional and supranational organizations aimed at integration rather than cooperation, State sovereignty is close to becoming an empty box.1 The rise of international organizations during the last century is without doubt one of the most important developments international law has witnessed. It is however doubtful that this evolution in and of itself has any bearing on the current traditional concept of state sovereignty.
This paper argues that instead of viewing regionalism and supranationalism as implying ipso facto a threat to state sovereignty, the form of the legitimacy of international organizations is determinant for the impact of international organization on the sovereignty of states. The question of the legitimacy of international organizations and the alleged threat that supranationalism and regionalism poses to the current conception of state sovereignty is of course closely intertwined with the type of international organization and the activity exercised by that organization. Both questions are indeed confined to those forms of supranationalism and regionalism which include the take-over of certain functions traditionally exercised by states, and thus go well beyond mere cooperation at the international legal level.