I looked at your thread. Indeed, I had responded to it back in January. I am commenter number 5. I didn't see a definition for the word "Citizen" in there anywhere. Do you have a link to the Oxford dictionary prior to 1770 so that we can see how they defined the word "Citizen" back in 1770? (Before Vattel's influence could have any effect.)
There was no OED prior to 1770. But if you look at the word entries I have previously supplied, you should be able to see how this works. They give a meaning and they follow it with dated usage examples. I would make you a copy of the entry for citizen, but my scanner is giving me trouble right now.
I already pointed out that the first example of the US usage tying a citizen to a state comes from 1538.
ML/NJ