Two different dynamics govern the autonomy of the European Union (EU) legal order. On the one hand, autonomy seeks to define what EU law is not, i. e. it is not ordinary international law. Positively, on the other, autonomy seeks to define what EU law is, i. e. a legal order that has the capacity to operate as a self-referential system of norms that is both coherent and complete. Yet the concept of autonomy of the EU legal order in no way conveys the message that the EU and its law are euro-centric and that the Court of Justice of the European Union (the ‘Court of Justice’) seeks to insulate EU law from external influences by building walls that prevent the migration of legal ideas. Autonomy rather enables the Court of Justice to strike the right balance between the need to preserve the values on which the EU is founded and openness to other legal orders. The autonomy of the EU legal order is thus part of the very DNA of that legal order as it allows the EU to find its own constitutional space whilst interacting in a cooperative way with its Member States and the wider world.