According to Article 25 of the UN Charter, member states of the United Nations are supposed to carry out the resolutions of the UN Security Council. The member states of the EU are therefore obliged to follow these resolutions, because all of them are also the member states of the UN. It is well known that the EU is not and cannot be a member of the UN simply because the EU is an international organization rather than a state. When the Security Council of UN makes a resolution and enacts economic sanctions against a third state, it will cause serious Problems, such as how could the member states of the EU implement the UN sanctions when the competence to it is taken over by EU which is not bound by the resolution. It is obvious that the member states of the EU should take on full responsibility under the UN law for the conduct of the EU institutions because the transfer of competences to EU does not exempt the member States from their responsibility under the UN resolutions. In order to overcome the internal division of competences the EU and the member states developed the complicated practices which combine the first pillar with the second. The Article will analyze the development of these practices and discuss the following questions: How does the EU transform the resolutions of the UN Security Council into Union law? What does the internal effect of the resolutions look like in the EU? Could the ECJ have the competence to decide the effect of resolutions of the UN Security Council in the EU legal order? Can the decision of the UN Security Council be subject to judicial review by the ECJ? The possible solutions of these questions can best be illustrated with reference to the Kadi case. In this case the ECJ claimed its jurisdiction to decide disputes concerning the EU legal order.