The focus of the article is on the activities of the European Union and the United Nations in the fields of peace and security, human rights and democracy. These represent not only crucial issues uniting both the EU and the UN in their external actions, but are also founded upon, or at least affected by, fundamental principles of international law. It is argued that a coherent strategy for achieving long term peace and stability in regional and international relations must be based on respect for these fundamental principles as well as rules of international law derived from these principles. Such principles are not just abstract legal constructs but are a reflection of the values that international actors – states, organisations and others – have held since the UN Charter ushered in a new world order in 1945. Situating both organisations within the international legal order should enhance the legitimacy and arguably the effectiveness of the two organisations whether they act singly or together. Increasingly, the activities of the EU and the UN overlap in matters of peace, security, human rights and democracy. This overlap has the potential to result in confrontation, as well as what would normally be aspired to – co-operation. It is therefore essential to identify the underlying principles and rules governing the organisations and their activities. It is argued that these principles and rules should be recognised and reinforced if we are to have organisational activity that is more than discretionary or arbitrary.