One point I haven’t seen brought up is that the definition of who is a natural-born citizen, if based on parentage, has necessarily changed since the Constitution was written.
At the time a married woman had no existence in law, as husband and wife were quite literally considered “one flesh” in the legal sense. This was true under common law, civil law and US law.
So when Ann married Barrack, Sr. she immediately lost her US citizenship and became a British and/or Kenyan citizen, if we use the legal principles in force at the time the Constitution was written.
This is untenable in today’s world, as we have significantly modified the legal position of women, especially married women. So any definition of NBC must be modified to reflect these realities. The question is how to modify it.
I won't get into a whole legal discussion here, but simply say that “natural born” is not synonymous with “native born,”. In fact, some people born on US soil to parents who are here legally are not US citizens at birth, while most children born here to mothers who are not here legally are US citizens at birth!
The basic concept is that a person can become a citizen in two ways; 1, "naturally,” at birth or 2, later, by application and operation of law. Then they can be become citizens as if (with a few exceptions) “natural” at birth. That operation of law allows them to become “naturalized,” i.e. as if natural.
Of course, the really interestingthing is that if Obama is not a natural born citizen, then he is not a citizen at all, because he never applied to become naturialized!