There was a question about Irish citizenship that reminded me that birthright Irish citizenship applies to both the Republic and Northern Ireland. So how many Northern Irish residents have taken out Irish citizenship? Why? And do any other countries give birth citizenship to areas that actually aren’t inside the country’s boundaries?
Because a significant percentage of Northern Ireland’s population believes that they are in fact Irish, not British, and the Republic is sympathetic to this.
People born in Northern Ireland (who meet certain requirements around parental residency and nationality) have the same entitlement to citizenship as people born in the Republic. There exists no process for someone in this situation to “take out” citizenship. In this respect Irish law does not distinguish between the territory of the Republic of Ireland and Northern Ireland. Since 1998, this is guaranteed under the terms of the Belfast agreement: “accepted as either Irish, or British, or both”; previously it followed from Article 2 of the Irish Constitution: “the entitlement and birthright of every person born in the island of Ireland to be part of the Irish nation”.
Applying for an Irish passport is a common (but not the only) way of asserting your Irish citizenship. However, you can of course be an Irish citizen without having any passport at all, or indeed while holding a British or other passport.
In practice, someone in Northern Ireland may or may not choose to apply for an Irish passport. However, this does not always imply an assertion of Irish national identity - for example a unionist may choose to apply for an Irish passport for practical reasons while still regarding himself or herself as fully British.
This is relevant in the context of Brexit - residents of Northern Ireland can continue to be EU citizens and carry EU passports even after Northern Ireland leaves the EU.