There is a large--and not entirely consistent-- body of law over when a corporation is a "person" under the Constitution and when it isn't.
Likewise, I understand that some old buildings are registered as "persons" in order to protect them from the wrecking ball.
This only makes my case stronger: if corporations cannot be ended (killed?) willy-nilly, nor historical buildings, then similar protections should be afforded actual human beings.
It would actually be instructive (and helpful if what you say is true regarding the current ambiguity of corporate law) to have all entities that can be declared "persons" described in one law. If this so offends people (i.e. associating humans with victorian houses and Enron) then maybe we might start to clarify things in these areas as well.