There is one more thing @longbelly : In line with the Good Friday Agreement there is the potential for a binding referendum leading to the unification of Ireland (i.e. secession of Norther Ireland from the United Kingdom)
The Good Friday Agreement committed the UK and Irish governments to respect the ‘principle of consent’.
This states that the two parts of Ireland have the right to be reunited, so long as that decision is “achieved and exercised with and subject to the agreement and consent of a majority of the people of Northern Ireland.”
If both Northern Ireland and the Republic of Ireland voted in favour of reunification, the Good Friday Agreement further specifies that "it will be a binding obligation on both Governments to introduce and support in their respective Parliaments legislation to give effect to that wish."
from the Institute of Government