In this final chapter of Part II, we analyse the key legal issues related to the allocation of international investment competence within the EU and examine their implications for policy efficiency and choices in external EU trade and investment relations. Following the Lisbon Treaty of 2009, the EU has gained competence for international investment treaty-making, which previously fell within the scope of the Member States’ competence. Given the relevance of international investment for the EU, on the one hand, and the cross-cutting nature of investment within the range of domestic policy areas on the other, the exercise of competences relating to foreign investment has been surrounded by controversies. Importantly, treaty-making procedure in the EU is not a matter of political inter-institutional preference but it is defined by the delineation of competences, grounded in primary law. The focus of our analysis in this chapter is placed on the internal EU institutional framework regarding competences between the EU and its Member States for investment and the conclusion of EU international investment agreements, and the role of the CJEU in defining the scope of EU policy. The content of EU international investment policy is then analysed in Part III.