EU external competence : rationales for exclusivity

The aim of this chapter is to offer a reflection on the rationales for determining that EU external competence should be exclusive, as developed first by the Court of Justice and later by the EU Treaties. In doing so it explores the differences between express and implied competences, the implications of these differences for exclusivity, as well as assessing recent institutional practice. The choice between express and implied external powers does not represent a straightforward choice between less or more exclusivity. But it does imply a difference in the rationale for, and implications of, exclusivity. And when external powers are justified by the existence of a body of EU legislation, the interactions between external and internal regimes mean that exclusivity is in turn likely to be required