I understand that you would like your son to be considered NBC but if he has a passport from another country then he falls outside what I understand the Framers to mean. Another country has a claim on his citizenship so his loyalty is divided. I don't think the Framers considered dual citizens per se but the principle that motivated them to insert the NBC Clause is easy to understand in this case - if more than one country can claim your allegiance then you are NOT NBC.
Does that not then give a FOREIGN country the right to determine who is a natural born citizen of OUR country? If they grant a child born here to two US parents are passport then that kid is not an NBC. But if that don’t then he is? That would seem to destroy the sovereignty argument at the base of the requirement, no?
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Passports have absolutely nothing to do with the question.
The are strictly travel identification, not citizenship documents.