An action for annulment under Article 263 TFEU must be available in the case of all measures adopted by the EU institutions, irrespective of their nature or form, provided that they are intended to have legal effects. In order to ascertain whether such measures produce legal effects it is necessary to look to their substance. In this regard, a decision adopted on the basis of Article 218(3) and (4) TFEU produces legal effects as regards relations between the European Union and its Member States and between the EU institutions. Thus, a Council decision authorising the opening of negotiations with a third State, such as the Decision of 13 May 2013 authorising the opening of negotiations on linking the EU emissions trading scheme with an emissions trading system in Australia, can be the subject of an action for annulment brought by the Commission, inasmuch as it sets out a precise and detailed procedure, concerning the negotiation of the contemplated agreement, which the Council seeks to impose upon the Commission.

As regards the conclusion of international treaties, Article 218 TFEU constitutes an autonomous and general provision of constitutional scope, in that it confers specific powers on the EU institutions. With a view to establishing a balance between those institutions, it provides, in particular, that agreements between the European Union and one or more third States are to be negotiated by the Commission, in compliance with the negotiating directives drawn up by the Council, and then concluded by the Council, either after obtaining the consent of the European Parliament or after consulting it. The power to conclude such agreements is, however, conferred on the Council subject to the powers vested in the Commission in this field. In the context of those functions, the Council and the Commission are nevertheless required to comply with the principle of sincere cooperation, which is of particular importance for EU action at international level as such action triggers a closely circumscribed process of concerted action and consultation between the EU institutions.

Where the Council has designated a special committee under Article 218(4) TFEU, the Commission must provide the special committee with all the information necessary for it to monitor the progress of the negotiations, such as, in particular, the general aims announced and the positions taken by the other parties throughout the negotiations. It is only in this way that the special committee is in a position to formulate opinions and advice relating to the negotiations. Having regard to the various functions of the institutions in the negotiation and conclusion of the agreements referred to in Article 218 TFEU, the Commission can be required to provide that information to the Council as well.

Consequently, an obligation in the Council decision authorising the opening of negotiations which provides that the Commission is to report in writing to the Council on the outcome of the negotiations after each negotiating session and, in any event, at least quarterly must be regarded as in conformity with Article 218(2) and (4) TFEU. Such an obligation also complies with the obligation laid down in Article 13(2) TEU that each EU institution is to act within the limits of the powers conferred on it by the Treaties. Likewise, it does not infringe the principle of institutional balance or Article 295 TFEU.

(see paras 62, 64, 66-68, 70-72)