Before the Good friday agreement you had to have irish parents to be an Irish citizen. Unfortunately for the population of northern Ireland they were not considered to be Irish since they were British Subjects by virtue of living in the north.
So the Government decides to pander to these people who want to claim citizenship as a show of... fuck knows what . As a result, the constitution of Ireland is changed to allow anyone born in Ireland (the Island, not the republic) to be a citizen.
Time passes, and Ireland, through no fault of its own, becomes rather prosperous and a rather attractive prospect for refugees and economic migrants alike because it has such an open policy on the citizenship issue. No one on planet Earth is entirely surprised at this because the previous change to the constitution was shockingly broad. Many people are left wondering what the hell was wrong with putting "children born to parents who are British subjects who have been living in northern Ireland for five years may be Irish citizens" into the constitution instead.
EDITED - Forgot this bit:
For a while we have a bit of a "problem" with immigration here. By "problem" I of course mean that our petty little nation of racist fucktards was finally forced into the 20th century (a little late I know) and forced to accept the reality that we are a part of the european community and the world for that matter.
Of course that's not to say that all our good, upstanding citizens were happy about this and judicious use of the media and "statistics" revealed that we had a massive problem with pregnant women coming over to Ireland, popping a baby out and then staying in Ireland on the basis that their child was an irish Citizen. Our "Justice" minister was having none of this and arranged to have not only the parents deported from the country but also the children who were irish citizens. Natch, a good chunk of this happened at the dead of night or the wee hours of the morning when in a particularly shameful episode of our history we rounded up a bunch of immigrants and shipped them "back to africa".
But the Irish government is still faced with a crisis of epic proportions...
Or not since it seems that all of the "proof" cited by the government in an attempt to justify having this referendum has proven to be complete bullshit - particularly the bit where the doctors in the Mater hospital maternity ward supposedly claimed that dozens of Nigerian women came in to have babies every week.
In predictable fashion though the Government ploughed on regardless and declared that we needed a referendum to get RID of the old provisions for citizenship. Despite the fact that the precise wording has yet to be worked out (to my knowledge, and it's nice to see them at least pretend to give it some thought this time) there are huge numbers of "VOTE YES" posters going up all over the place. Naturally there is a marked lack of reasons why we *should* VOTE YES in this referendum given.
But thanks to the referendum commission (an independent body set up to combat fucking debacles like the double nice referendum we can now learn that this referendum is not a matter of changing the wording in the Constitution, they ACTUALLY want to remove all references to the entitlement of citizinship and make the whole thing a legislative matter - therefore allowing the government to determine who does and does not get to be a citizen (I could be wrong but I'm thinking that the Romanians and Nigerians wouldn't be on that list for example). More worryingly they want to be able to introduce a means to strip people of their citizenship. Given the government's attitude to dissent lately I don't like the thought of that.
Heck, even if that weren't an issue, would you really want those morons deciding who could be in our gang?
 Note to Americans - the Nice referendum (that's nice as in the french town pronounced Niece as opposed to nice/pleasant) was a matter voted on by the Irish public to determine whether or not we would pretty much hand over control of the country to Europe. We voted no the first time and the government decided that we obviously didn't understand the question (which was fair enough, they did a pretty good job of fucking up the information channels in that regard) and held another one a year later.