if the exchange serves any USA residents, federal regulators claim jurisdiction. if they serve new york residents, new york regulators do the same. (although the feds are a lot scarier!)
1broker didn't operate from the USA in any capacity, but they openly served USA customers so the feds shut them down. isn't that the same thing?
What if you have a person orbiting on a space station and they wish to place a few trades online?
Maybe that somebody was born on a space station, and they never even visited Earth before.
Will they be banned from trading?