Automatic Entry

From the Irish Times:
"State to seek automatic EU entry for NI in event of unification"

The Government is to push for a commitment that Northern Ireland will be given speedy admittance to the European Union in the event of Irish unity.  Sources have said the talks on Britain’s departure from the EU, due to begin by the end of March, must take account of the prospect of a future Border poll. A referendum on Irish unity is allowed for in the Belfast Agreement but only if certain conditions are met. The example being cited, and the argument that will be deployed by the Government, is that of East Germany becoming an automatic member of the then European Community on the day of German reunification in October 1990.  One well-placed source said the Government will “look for the same thing in relation to the North”.  “You could be talking in 20 years’ time if the people of Northern Ireland decide to join up,” said a source.

^ I think that should Northern Ireland vote to leave the UK and become a part of the Republic of Ireland then NI should automatically become part of the EU - even if the UK has left the EU by then. The case for East Germany directly mirrors that of NI  - if NI reunites with Ireland. ^

http://www.irishtimes.com/news/ireland/irish-news/state-to-seek-automatic-eu-entry-for-ni-in-event-of-unification-1.2918722