I imagine that is is due to the fact that this is not a matter of statute law at all. It is a matter of Constitutional definition, and Constitutional words are not defined by statute. If they could be, we could do away with the Amendment process and just redefine select words and phrases any time we wanted to mean whatever we decided they should mean. That is decidedly NOT the case.
Well, if that is the case, we can permit the nine members of the SCOTUS decide on the definition of “natural born citizen.”