An in-out EU referendum in 2017
A UK referendum vote on EU membership will not be ‘illegal’ and the UK will not be prevented from leaving the EU in the event of a negative vote in 2017.
Article 50 of the Treaty on European Union (TEU) provides for a Member State to leave the EU if it wishes, without needing the permission of the other Member States. QMV would be used by the other Member States to agree the terms of exit for the withdrawing State. Article 50 TEU states:
1. Any Member State may decide to withdraw from the Union in accordance with its own constitutional requirements.
2. A Member State which decides to withdraw shall notify the European Council of its intention. In the light of the guidelines provided by the European Council, the Union shall negotiate and conclude an agreement with that State, setting out the arrangements for its withdrawal, taking account of the framework for its future relationship with the Union. That agreement shall be negotiated in accordance with Article 218(3) of the Treaty on the Functioning of the European Union. It shall be concluded on behalf of the Union by the Council, acting by a qualified majority, after obtaining the consent of the European Parliament.
3. The Treaties shall cease to apply to the State in question from the date of entry into force of the withdrawal agreement or, failing that, two years after the notification referred to in paragraph 2, unless the European Council, in agreement with the Member State concerned, unanimously decides to extend this period.