What makes a fighter's nationality?

[Steak]

Bear in mind that nationality doesnt really matter at all, just judge the individual. but there have been some things Ive been confused about.

some people consider Darchinyan Australian because hes living in Australia, but he was born in Armenia
most people consider Bute Canadian because he lives in Canada, but he was born in Romania.

so does that mena that America really does have a Heavyweight champion? cause Oleg Maskaev lives in the USA with his family, and I believe he said he was a United States citizen before the 2nd Rahman fight, cause he brought his papers and everything and was showing it to everyone there.
but most people consider him Eastern European. and you see this happen a lot, a lot of fighters move to the US or another such country, but people tend to look at them from their old nationality.

dont take me the wrong way, Im not trying to pull some ridiculous logic to try and make it look like America has a heavyweight title or anything hahaha, but just curious, how do yall determin a fighters nationality?
Is it where they live? What country they are legally citizens of? Where they were born? How alike they are to a certain nation? Or is just what they choose? ...or maybe what it says on boxrec?

[BIGPOPPAPUMP]

Depends on the fighter. I think Lennox Lewis hurt his marketability by one year being Canadian, another year being Jamacian and then going back to being a UK fighter and playing between the three.

[Dick-Sucker]

A combination of current residency, where you most fight, were you were born etc etc.