In this article it is discussed how the European Union's use of treaty-making powers and other external relations competences has contributed to the establishment of human rights as customary international law and makes it more likely that democracy and modern concepts such as good governance, precaution and sustainable development, will also gain this status. A specific focus of attention is on the EU's vision of the aforementioned rights and principles as a limit to State sovereignty. It is shown that the EU promotes an interventionist approach, which allows for proportionate responses to violations of peremptory norms by or in sovereign States. Since this view is expressly subscribed by a vast number of the EU's treaty partners, the EU's vision of State sovereignty is becoming a significant element in the development of the international legal order.