Are you implying that because Bellei, born to an Italian father and an American mother in Italy has any bearing on the definition of a natural born citizen?
Bellei’s citizenship WHOLLY relies upon the naturalization laws as his father was not an American citizen and Bellei, being born in the country of his father’s citizenship, that citizenship IS subject to revocation because Bellei did NOT comply with US law, the residency requirement upon his coming of the age of consent and the selective service requirements. The court made its determination based upon feudal law of perpetual allegiance, the only problem with that, it is the State that determines when that allegiance has been broken and yet they do not even uphold that doctrine of their non-existent laws they apply.