This paper investigates two questions: what prompted the Member States of the EU to define the Union’s competence in the field of foreign policy during the treaty reform process and why did this question never become a matter of sustained concern before the Lisbon Treaty. The chapter develops an answer to these questions by relying on two concepts borrowed from international relations scholarship, legalization and organization development, and argues that the institutional design of European foreign policy cooperation is governed by what we may term the Goldilocks Principle.
