"Might it be legal in the long run? No."
That's the whole point!! If it is an illegal act, you have either (a) a constitutional crisis, or (b) final disposition that kills Terri anyway.
Taking physical custody at this point does nothing unless you can ALSO legally overturn the Judge Greer ruling that is effectively a death sentence. That's why Congress passed the law the way they did, to get a 'de novo' Federal review. But the Federal Judges arrogantly snubbed the law in this case, pretending that the issues had been reviewed.