So if Bush proposed an amendment to send all the nations Irish-American population to internment camps to make them grow potatoes, he'd be well within his rights as the president, right?

I havent attempted to halt the 'march of progress' of anyone. I dont care who marries who. It isnt my business if a man marries his sister. And when it becomes such a problem that many people are in love with their kin and wish to marry them, then it will become a constitutional issue. As yet, that situation doesnt exist, now does it?