Sure, and that's one of the current avenues of appeal Terri's parents are pursuing. It's a WAY better argument than the religious liberty one which is practically exhausted.
Unfortunately, Judge Greer has held that the guardianship issue shouldn't be resolved until after the issue of whether Terri should be put to death, since it would be pointless to look into the guardianship issue if Terri's death renders it moot.
What's important is not the particular issues raised here or there, but rather that it looks as though Felos may have overplayed his hand. I am reminded of the Book of Exodus, where the Red Sea parts, and God hardens the hearts of the Egyptions to follow the Israelites. I suspect the Red Sea will be closing shortly.
It's important to keep praying, and keep spreading the word to the populace and to the politicians, but I think I may be starting to understand His plan. Had He allowed Terri to be saved earlier, that would have saved one life. By letting things get where they are, He may save thousands.