Within the debate on the attribution of international responsibility to international organizations and/or its Member States, the role that the internal rules of the organization may play is not settled. The competence-based approach, where a relationship is supposed to exist between the eu/Member States’ division of competences and international responsibility, and the normative control doctrine, where the Union is deemed responsible for the actions of its Member States in the course of implementing eu law, are at the heart of such debate. This contribution aims to investigate whether the recent practice concerning the Union’s international responsibility in the fields of fisheries and investment adds clarifying elements. The analysis will specifically focus on the 2015 itlos Advisory Opinion (Case No 21), an award under the Energy Charter Treaty (Electrabel v Hungary), and the investor-to-state dispute settlement mechanisms laid down in the recent eu bilateral investment agreements. Although one of these cases seems to implicitly recognise the normative control as a rule for the attribution of conduct to the eu when its Member States act implementing Union acts, what is missing, however, is a clear and deep debate on its specific elements. Discussions on a competence-based approach and normative control seem generally confused at the eu as well as at the international community level, suggesting that important opportunities have been missed to properly re-open the debate on the role of the organizations’ internal rules for the attribution of international responsibility.