I don't see that any just authority of the state of Florida is being displaced by the effort of Congress to ensure that Terri's right to life is honored and that civil rights claims on her behalf are given a hearing in the federal courts. By "just authority of the state of Florida," I mean the authority of the people of Florida to make laws through their elected representatives, subject to the provisions of the state constitution and the Constitution of the United States. I am not impressed by appeals to "federalism" to protect the decisions of state court judges who usurp the authority of democratically constituted state legislative bodies by interpreting statutes beyond recognition or by invalidating state laws or the actions of state officials in the absence of any remotely plausible argument rooted in the text, logic, structure, or historical understanding of the state or federal constitution. The fact is that, under color of law, Michael Schiavo is seeking to deprive Terri of sustenance because of her disability. Under federal civil-rights statutes, this raises a substantial issue. It cannot be waved away by invoking states' rights.
The federalism argument is more plausible in the case of Oregon's assisted-suicide law than it is in Terri Schiavo's case. It wasn't some judge in Oregon who manufactured a right to assisted suicide or claimed to find it hiding in a penumbra. I think the people of Oregon made an unwise, indeed, tragic, decision, but it was a decision made by the democratically constituted people of Oregon. Whether or not there are legitimate grounds for the federal government to override that decision, the federalism argument for not overriding it is far weightier and more serious than it is when trotted out as a reason to keep Congress from acting to prevent Terri Schiavo's being starved to death at the command of her husband.
The other thing that Congress is being accused of is interfering in a family decision. Now look: Terri Schiavo has been abandoned by her husband. Michael Schiavo took a vow to be faithful to Terri "in sickness and in health, forsaking all others, 'til death do us part." But he has not been faithful; he has not forsaken all others. He has set himself up in a marriage in all-but-name with someone else, a woman with whom he already has two children. He has disrespected Terri and, indeed, forsaken her. Now he is seeking to bring about her death by starvation. Notice something wrong with this picture? Terri's parents and siblings, by contrast, have never abandoned her. They are prepared to shoulder all the burdens, including the financial burdens, of caring for her. They want to provide the therapy that many medical people who have observed Terri, whether at the bedside or by videotape, believe can help her. No one expects a full recovery, but it may be possible for her to make genuine progress. That possibility will be foreclosed, however, if she is killed by deliberate starvation before it can begin.