I would think that if it could be proven that his claims about Terri's "wishes" were a fraud upon the court, that would prevent him from using any resulting rulings as justification for starving her to death.
Certainly any murder prosecution would end up being dominated by arguments about what a jury could or could not be told, and the resulting verdict would depend more upon what information was withheld and upon the jury instructions than upon any real facts of the case. To my mind, the proper question for a jury would be whether it was plausible that Michael's efforts to have his wife dehydrated were at least 51% predicated upon a bona fide desire to carry out her wishes, rather than upon craven motives including, but not limited to, the concealment of evidence, the acquisition of her trust fund, revenge upon her parents, etc. Nearly all of Michael's actions should be fair game in ascertaining that.
Incidentally, my use of first names for some people (e.g. "Michael", "Terri") and last names for others (e.g. "Felos") is predicated not upon familiarity, but upon a desire for brevity without ambiguity. There are multiple people in this saga named Schiavo, and multiple people named George, but there is only one each of "Michael", "Terri", or "Felos".