He is only her "legal guardian" because he is considered her spouse under the law. In light of the fact that he has taken up with another woman and had two children by her, he has -- for all intents and purposes -- abandoned his wife. As far as I know, shacking up with another woman and having two children out of wedlock would be irrefutable grounds for divorce in any state in the U.S.
Terri has never been given "due process" in this case, as she has never had her own legal counsel appointed to represent her. She needs a lawyer appointed to act on her behalf, and the first thing that lawyer must do is file for divorce on the grounds that I just described.
What else should the Court consider if not the law?