So my obvious question is...what did I get wrong this time?
I honestly don't think it's wrong so much as all of us have been mislead.
In your earlier post, when speaking of Vattel:
215 Children of citizens born in a foreign country... ...the place of birth produces no change in this particular, and cannot, of itself, furnish any reason for taking from a child what nature has given him; I say "of itself," for, civil or political laws may, for particular reasons, ordain otherwise.
That's quite true....BUT
The federal government is neither a civil or political entity, it is an 'administrative organ' [as Tucker put it] made to operate ONLY in designated areas.
One designated area is Article 1, Section 8, Clause 4;
To establish an uniform Rule of Naturalization.
Nowhere in that clause is found the word 'citizenship'. That's because the citizenship the Constitution speaks of, whether natural born OR naturalized, does not emanate from the federal government, it emanates from the civil States.
So Vattel's words DO apply, they just don't apply to what most people think they do.....the federal government.
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Civil and administrative are two totally separate kinds of 'law'. The Founders used them purposefully to 'secure the Blessings of Liberty to themselves and their Posterity'.
The only other option would be to believe that the Founders pledged their lives, fortunes and sacred Honor and then fought a War just to write down less than 5000 and trust the judgment of the people elected to do the 'right thing'.
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Be that as it may [and IMHO] McCain would be eligible according to Vattel's § 217.
Natural born citizenship is inherited. The location of that inheritance doesn't matter.