All Well in Libertopia?
I would have thought that when I wrote: "For the record, I think they are wrong for supporting it, but just because I think it's imprudent to get involved in a single family's case in this way, particularly when the odds of success appear remote" in my original post I was signalling that I thought this was a bad law. Not all bad law is a violation of federalism, which is not just a catch all for "stuff one likes about the law as a (choose one: conservative, libertarian, etc.)." Indeed, even properly construed, federalism is hardly absolute and its contours are not altogether obvious, so that one always has to ask why federalism here and why not there. Quite clearly, in this case, it was legitimate to wonder about due process. I don't think we needed more than the Supreme Court's cert. review (which was already available), so I don't think the law should have passed. But there is nothing so marvelous about the certiorari process that it threatens the republic to have altered it here, and nothing so federalist about it that to alter it, however improvidently (shall I say again I would not have voted for this law?), is to threaten federalism.
I also think that if the law had been written in such a fashion as to ask the courts what its authors probably intended, the consequences for federalism and the rule of law would be as you (and Charles Fried in the NYTimes) have suggested. I look at this case, in this sense, as a vindication of textualism. The bill that passed, probably for good reasons (some responsible legislators who were willing to support a reasonable extension of jurisdiction, rather than an untenable one), simply does not, as you appear to acknowledge, do much that is so radical. It certainly does not permit, let alone require, the setting aside of state law.
You may have more insight into what Sen. Frist and others in the majority intended. I'm interested, as a textualist, in what they passed. What they passed did not amount to a Congressional aggrandizement or a de facto appellate court, because, in fact, they did not direct any substantive outcome. They got what they asked for--however much that may differ from (a) what they wanted or (b) what they wanted to ask for...[Cf. this part of an exchange between Orin Kerr and Hugh Hewitt on similar issues.]
So I hope we are clear that I share your disappointment that people supported this legislation. I just do not see the grounds for opposing it as arising so much from federalism and the separation of powers as from the bad precedent (which doesn't disappear by their having written "this is no precedent" into the bill) for behavior by the national legislature, from the false hope that it gave the Schiavo family, given that nobody was really able to suggest there was a federal case here likely to win on the merits (including Judge Wilson in his dissent).
P.S. There is a St. Thomas More, who is a hero of mine, but I do not claim St. as part of my pseudonym!