From the BBC (here):
European Commission President Jose Manuel Barroso has said it would be "extremely difficult, if not impossible" for an independent Scotland to join the European Union.
In his interview with Andrew Marr, Mr Barroso said: "In [the] case [that] there is a new country, a new state, coming out of a current member state it will have to apply."
He said it was important that "accession to the European Union will have to be approved by all other member states of the European Union."
He went on: "Of course it will be extremely difficult to get the approval of all the other member states to have a new member coming from one member state."
If Scotland were to become a new state, why would not also the rest of the UK? Splitting legal hairs, I know, but that’s what the arguments come down to. After Scottish independence, the rest of the UK would manifestly not be the same state it was before independence. If the Barroso doctrine is correct for Scotland, why would it not also be correct for the rest of the UK? Thus leading to the intriguing prospect of both the former parts of the UK having to apply …
It is not of course for Barroso to decide these matters. Nor indeed the ECJ, as nothing in the Treaties sets out what should happen in the event of the disintegration of an existing Member State. The one aspect where Barroso is correct is that it will require to be sorted out - politically - in the Council of Member States.