The principle of loyal co-operation: a 'master key' for EU external representation?

The principle of loyal co-operation has in recent years become a recurrent instrument in judicial discourse for shaping the external relations of the Union. This paper explores how the Court of Justice made recourse to such a principle in defining the EU international presence and the role it plays in ensuring its representation in international fora. It will first outline loyalty duties emerging from the joint representation of the Union and its Member States at international level, such a representation being the traditional context for invoking the EU loyalty clause. Then, issues concerning the exclusive participation of Member States in international fora will be faced. In addition to these aspects, the paper will analyse the mutual nature of duties stemming from the principle of loyal co-operation and their impact on the EU external action. It concludes that the way the Court views the principle of loyal co-operation as a general tool for ensuring an effective external representation of the Union shows some structural limitations that might lead to political tensions between Member States and EU institutions. First, although the codification of the mutual nature of loyalty duties by the Lisbon Treaty, the case-law still remains essentially focused on defining the States’ obligations. Secondly, since States’ duties are mainly conceived as abstention obligations, the Court’s approach is likely to cause in some circumstances (especially in case of Union’s inaction) an excessive limitation of their foreign relations powers that may ultimately undermine the multifaceted governance of the external action of the Union.