“The laws of the United States fall under three classifications: treaties made under the authority of the United States, the law of nations,(Vattel), and the Constitution and statutes of the United States.” John Jay
And where do we find the meaning of the terms used in the Constitution? Alexander Hamilton told us that we should look to the legal language of the country that we derived our legal system from - England, and the English common law.
So when the Constitution says "natural born," the definition of that term, according to Alexander Hamilton (as well as due to the fact that it occurs NO PLACE ELSE) is to be found in the English common law.
That's it. Period. It's not that hard.