Consolidated version of the Treaty on European Union/Title IV: Provisions on Enhanced Cooperation
Article 20 
(ex Articles 27a to 27e, 40 to 40b and 43 to 45 TEU and ex Articles 11 and 11a TEC)
1. Member States which wish to establish enhanced cooperation between themselves within the framework of the Union's non-exclusive competences may make use of its institutions and exercise those competences by applying the relevant provisions of the Treaties, subject to the limits and in accordance with the detailed arrangements laid down in this Article and in Articles 326 to 334 of the Treaty on the Functioning of the European Union.
Enhanced cooperation shall aim to further the objectives of the Union, protect its interests and reinforce its integration process. Such cooperation shall be open at any time to all Member States, in accordance with Article 328 of the Treaty on the Functioning of the European Union.
2. The decision authorising enhanced cooperation shall be adopted by the Council as a last resort, when it has established that the objectives of such cooperation cannot be attained within a reasonable period by the Union as a whole, and provided that at least nine Member States participate in it. The Council shall act in accordance with the procedure laid down in Article 329 of the Treaty on the Functioning of the European Union.
3. All members of the Council may participate in its deliberations, but only members of the Council representing the Member States participating in enhanced cooperation shall take part in the vote. The voting rules are set out in Article 330 of the Treaty on the Functioning of the European Union.
4. Acts adopted in the framework of enhanced cooperation shall bind only participating Member States. They shall not be regarded as part of the acquis which has to be accepted by candidate States for accession to the Union.