Here is a comment that I appended to a discussion of the Terri Schiavo case at Patterico's blog, which is oriented to discussions of perspectives within the law. Please let me know what you think, especially if you are a legal beagle like the great Hunter Baker.
May I offer a legal theory that I believe could have been applied here with a modicum of creativity. Namely, the idea of the Federal Government appointing a guardian to supersede the State guardian. Now this idea is of the "out-of-the-box" variety, so let me give it a moment of development.
It seems clear that the status of "citizen" applies only as a description of a relationship with the Federal Government. One is a citizen of the United States and a resident of, say, Florida (like Terri Schiavo and me).
Theoretically, one could be a citizen of the United States and not be a resident of any state. Sell your house and move for a full year to another country and I don't believe that any State can claim jurisdiction over you as its resident.
Now, the institution of guardianship is usually left to the State to apply, within the context of its protection of residents. However, in theory there is no reason that the Federal Government cannot appoint a guardian for a person's rights of citizenship. That guardian would not be answerable to any State court.
Arguably, this might even be doable by order of the Executive branch alone, but it could certainly be done by the Legislative. The Congress could have passed a bill appointing Jeb Bush or some such personage as the guardian of Terri Schiavo, and the authority of Michael Schiavo would have been superseded and consequently circumvented.
No? Let's hear from all those finely honed legal minds.