Article 3 TFEU

1. The Union shall have exclusive competence in the following areas:
(a) customs union;
(b) the establishing of the competition rules necessary for the functioning of the internal market;
(c) monetary policy for the Member States whose currency is the euro;
(d) the conservation of marine biological resources under the common fisheries policy;
(e) common commercial policy.

2. The Union shall also have exclusive competence for the conclusion of an international agreement when its conclusion is provided for in a legislative act of the Union or is necessary to enable the Union to exercise its internal competence, or in so far as its conclusion may affect common rules or alter their scope.