Treaty of Lisbon: Article 1 - Treaty on European Union… (2007)
“ Any Member State which, at a later stage, wishes to participate in the permanent structured cooperation shall notify its intention to the Council and to the High Representative. The Council shall adopt a decision confirming the participation of the Member State concerned which fulfils the criteria and makes the commitments referred to in Articles 1 and 2 of the Protocol on permanent structured cooperation. The Council shall act by a qualified majority after consulting the High Representative. Only members of the Council representing the participating Member States shall take part in the vote. ”
