Banning US citizens is clearly in the Terms of use on WEX.nz for all to see. I would call that set in stone.
Speaking of banning US citizens, it seems that Bitfinex is terminating trading, deposits, and withdrawal functionality for U.S. individual customers by November 9, 2017.
I wonder how many other crypto exchanges will take that hard line?
Remember, though: BTC-e was indicted for operating an unlicensed money service business and fined $110 million for it. Bitfinex has been doing exactly that---with no MSB licenses in any of the 50 states---for something like 5 years. They are pulling out of the market now that law enforcement moved against BTC-e and regulators (like the CFTC and SEC) are ruling on ICO tokens. But we'll have to see if it's too little too late. I suspect that the various US agencies are months or even years into investigating Bitfinex. Pulling out of the market now doesn't erase past violations.
This isn't the wild west anymore. It's possible that exchanges might get away with flouting the law in the early years. To do so now is suicide for any company that wants to remain in existence five years from now. The message to exchanges operating in the US is clear: get proper licensing, or get out.
I think BTC-e got targeted before Bitfinex because they were run by Russians. The Admin on BTC-e said it was political, probably referring to the Russiaphobia that's been dominating the US media since Trump got in. The DoJ press release started off with "Russian National" as the first two words in the headline before mentioning the actual topic.
Bitfinex might be getting out of the US just in time, though I doubt they are being targeted because they are not "Russian Nationals".