We had to have a referendum because it's in our constitution that any major changes to EU's constitution require a referendum. Which is a good thing for two reasons:
1. All the major political parties in Ireland are majorly pro-EU. Only fringe groups like the Socialists and Sinn Féin are anti it, and tbh, nobody votes for them.
2. If the Irish politicians are left to their own devices, they will sign us up to everything, and Irish people will, by their nature, complain for a few days and then accept it. A simple example: Five years after metrication was completed in this country, something that very few here wanted, Irish people are still dividing by 8 and multiplying by 5 on roads to figure out how far they really are from their destination and newbie shoppies are still wandering to the butter isle to figure out how to cut a pound of ham at the deli counter.
And that's a major reason why I voted no. Not because the EU is that bad, on the contrary it's done a lot for us, but because I don't trust our own parties to be left to their own devices in Brussels. I'm still making my mind up how to vote next time, and it's very interesting to hear others against it, because it has been painted here as us holding the rest of Europe up. The Treaty itself is pretty hard to get through; a famous comment by one of our MEPs was that you'd "be mad to read it.", so a lot of people really don't know what they're voting on; I only partly understood bits of it, but I think one of my objections at the time was the amazing vagueness of sections of it.