A citizen born within the confines of the United States of parents who are citizens can lose that citizenship under certain conditions, those conditions being contingent upon the deliberate actions of the citizen thus born to officially renounce that citizenship.
That there was by Act of Congress conditions placed upon children born abroad of citizen parents makes those children no less citizens, thus stating that they be not "natural born" because of Congress's constitutionally supplied power to stipulate conditions of residency must be met in order to not lose citizenship acquired at birth, does not equate with being not "natural born" citizen.
