The problem is that the US courts ruled that US law does apply in Ireland because Microsoft has a presence in both countries.
And you think that somehow the ruling of a US court absolves Microsoft from Irish law?
Yes but these aren't 2 distinct entities. Does MS Ireland own MS US, or are they wholly separate entities, or does MS US own / control MS Ireland? It would seem the latter. I'm sure there's all kinds of shenanigans done for tax purposes, etc, but its part of MS, nonetheless, and the parent is US based, and under US legal jurisdiction.
That said, I hope they loose on this. A really bad precedent would be set and probably be detrimental to long term US business doing anything outside the US.