No, what I'm not accepting is your position that citizens at birth and natural-born citizens are somehow different. If one is a citizen at birth then they don't need to be naturalized and are therefore what the Constitution calls natural-born citizens. If the Constitution identifies a third class of citizenship then I'm not finding it.
Congress can naturalize persons and grant them citizenship at any time in that person’s life and requiring any process or none.
The first (where born) is combined with the other 3 to determine whether or not a child is a citizen at birth. There are laws written to govern every situation - except one. The only situation not covered by positive law is when a child is born in a country, and both parents are citizens of that country. Why? Because no law is required, the child is a citizen ‘naturally’. 'Natural Born Citizen' simply means, a person born a Citizen according to the law of nature.
- Born in or out of a country.
- Both parents are citizens.
- One parent is a citizen.
- Neither parent is a citizen.
What is important about the 'law of nature'? There is a legal term Jura naturæ sunt immutabilia - and it means, "The laws of nature are unchangeable".