IF Scotland eventually leaves the United Kingdom, then would it continue to be a member of the European Union? Further, would England/Wales/Northern Ireland (EWNI) remain a member given that it is currently the United Kingdom of Great Britain and Northern Ireland which is a member. These questions have been under consideration for some time as is shown by Commons Library Note of 8th November 2011 - Scotland, Independence and the EU.
The Treaty on European Union (TEU):
Article 49 of TEU states:
"Any European State which respects the values referred to in Article 2 and is committed to promoting them may apply to become a member of the Union. The European Parliament and national Parliaments shall be notified of this application. The applicant State shall address its application to the Council, which shall act unanimously after consulting the Commission and after receiving the consent of the European Parliament, which shall act by a majority of its component members. The conditions of eligibility agreed upon by the European Council shall be taken into account.