And Irish citizenship, which means that for nearly all purposes, his US citizenship will be irrelevant to how he is treated under Irish law. Dual citizenship complications are more an issue in third countries. If you are a citizen of the country you happen to be in, that usually trumps everything else.
Unless Ireland values its US relationship more than its citizens.
It's up to the judiciary and not the government.
And if he doesn't like the courts' decisions (presuming he goes to the supreme court) he can then take his case to Europe, afaik.