This is what SO many people fail to understand...it isn't the location of the birth, or any paperwork concerning the birth, it's the citizenship of the parents that determine the citizenship of the child.
There are two arguments. One, if he was foreign born, his mother was too young to confer citizenship per the law of 1961.
Two, that he needed to have both parents be US citizens.
The first is more clear cut, IMO. The second is what Donofrio’s and Apuzzo’s cases are based upon. But it is certainly something that the courts might reject on merit.