Recent efforts in the United Nations to establish a comprehensive system of international criminal repression by creating a permanent international criminal court are by no means free from doubts regarding the possibility ever to enforce such law. The preamble of the draft statute prepared by the International Law Commission states the basis on which the court is to assert jurisdiction in an ambitious manner: it is the ``International Community'', joining against ``the most serious crimes of international concern''. The project cannot, however, ignore decades of realist criticism against the assumption of the existence of an international community that is ready to accept an international criminal jurisdiction. In the negotiations, this contradiction is dealt with by a technique provided with an ambiguous name: ``complementarity'', i.e. the coordination of the tasks of the international and domestic jurisdiction. The writer discusses the various ideas and proposals presented under the heading of ``complementarity'' in order to examine the tension between communitarian and sovereignty-based strands in the international project to create an effective criminal jurisdiction.