When in Europe: Customary International Law and EU Competence in the Sphere of External Action

European Union law must be interpreted and its scope delimited, to the extent possible, consistent with the relevant rules of international law. Article 3(5) of the Treaty on European Union (TEU) provides that “the EU shall uphold and promote … the strict observance and the development of international law.” A similar legal commitment can be found in the constitutions of most EU Member States, which in some cases is about delegation of powers, whilst in others it concerns the achievement of global objectives. Article 3(5) of the TEU is also reminiscent of the judicial canon laid down by the United States Supreme Court inCharming Betsyregarding the affirmation of international norms by the Congress. TheCharming Betsydoctrine of statutory construction requires national legislation (an American statute) to be construed so as not to raise conflict with international law where possible.