NBC requires no naturalization or law, it is the essence of unquestionable being.
A child of 2 citizen parents being born on the soil leaves no doubt, others require statutes.
The Naturalization power of Congress, granted by the Constitution, enables them to say who must be Naturalized, so therefore, they have to identify who does NOT have to be naturalized.
According to those laws, children born overseas to citizen parents do NOT have to be naturalized. Their citizenship is native, natural, by birth, by blood.