It is not codified anywhere I'm aware of.
...but the fact is, that statement comports with the original intent of the Framers of the Constitution.
OK, so point out where they defined the difference.
>>> "OK, so point out where they defined the difference." <<<
Perhaps this comment I found (below) on Leo Donofrio's Natural Born Citizen blog will help. It contains a case reference which may also shed some light on this, as well as a quote from former Chief Justice William Rehnquist:
>>> "Historians need to help here. Remember, Congress was given the authority to regulate naturalization. It was the time of the French Revolution. Napoleon would soon be Emperor of France. It was his Napoleonic Code that would make citizenship by blood or descent the law of all Europe (except Great Britain, although by 1860, Great Britain would begin to adopt descent, and did so fully by 1948)
In the U.S., Africans were slaves, persons held as property. Africans were American-born, but NOT citizens.
In 1866, the Civil Rights Act made new freemen citizens, not by naturalization, because they were not foreigners, but by appeal to the natural-born clause in Article II as the qualification to be President of the United States. It was the discussion of citizenship in United States v. Rhodes, 27 F. Cas. 785, at 790 (1866) that confirmed the logic of this decision: If born subject to the jurisdiction of the United States, then a citizen.
Justice Rehnquist (before he became Chief Justice) pointed out that there were 11 instances in the Constitution a document noted for its brevity that address the citizen-alien distinction.
Clearly, this matter was vitally important to the Framers, and to every Court and Congress since. It will be important in this case, too." <<<