The Northern Ireland / Free Derry one...
Looking at the lyrics, it could be about either, but I have a feeling that with U2's Irish background it is likely to be the latter. -- The Anome
Plus there are numerous interviews (and some onstage hectoring) by Bono which make it perfectly clear which one they're talking about...(e.g. http://politics.guardian.co.uk/devolvedpolitics/story/0,9137,582283,00.html)