You can of course point out this law? (Hint: there is none. No statute law defines "natural born citizen". Citizen, sure, but not natural born citizen.
It's quite possible that even based on the known facts, that his father was a Subject of the British Crown at the time of his birth, that he is not a natural born US citizen, regardless of where he was born. He would be a citizen, under both the law and the 14th amendment, but possibly not a natural born citizen. There 's just no statute or (US) case law on the matter, because the only time the difference matters is in eligibility to the Office of President. There's only been one other case where it seems, well after the fact that the President was not born to US citizen parents. And in that case, Chester Arthur, his father did become naturalized well before he became President (by succession, not election, he had been VP when the President died). But he hid that fact when he ran for VP and after he became President. BHO's father, and stepfather for that matter, never were, nor never became US Citizens.
S.301 of the Immigration and Nationality Act (INA).
Citizenship is acquired , and "naturally born" is a prima facie assumption.So the question is what is "Unaturally born?"
Many servicemen and women have children abroad foeign postings, and this is how they obtain citizenship. But it would be rather gauche to suggest that hey are NOT naturally born in most instances of citizenship law contests involving the issue ( ie. qualifying for an SS number etc.) Of course one of the areas where that definition is an issue is in Article II , section 1 of the constitution.
There is a reason it is not defined. It simply has not had to be, yet.
Perhaps an Obama case will do so.