In December I asked the following question of the European Commission:
Could the Commission advise me whether the Scottish Government, in the event of Scotland declaring independence from the United Kingdom, would be obliged to reapply for membership of the EU in its own right?
If so, would the Scottish Government, in accordance with the Treaty of Lisbon, then be obliged to make preparations for the adoption of the single currency?
Jose Manuel Barrosso answer:
As the Commission has noted in its reply to written question E-008133/2012, it is not its role to express a position on questions of internal organisation related to the constitutional arrangements of a particular Member State.
Scenarios such as the separation of one part of a Member State or the creation of a new state would not be neutral as regards the EU Treaties. The Commission would express its opinion on the legal consequences under EU law upon request from a Member State detailing a precise scenario. As the Commission has confirmed in the reply to written questions P-009756/2012 and P-009862/2012, the EU is founded on the Treaties which apply only to the Member States who have agreed and ratified them. If part of the territory of a Member State would cease to be part of that state because it were to become a new independent state, the Treaties would no longer apply to that territory. In other words, a new independent state would, by the fact of its independence, become a third country with respect to the EU and the Treaties would no longer apply on its territory.
Under Article 49 of the Treaty on European Union, any European state which respects the principles set out in Article 2 of the Treaty on European Union may apply to become a member of the EU. If the application is accepted by the Council acting unanimously, an agreement is then negotiated between the applicant state and the Member States on the conditions of admission and the adjustments to the Treaties which such admission entails. This agreement is subject to ratification by all Member States and the applicant state.