Honestly I don't understand @cciresi's position. As far as a I know anti-boycott regulations have primarily (only?) been used to prevent US companies from not doing business with Isreal. China & Russia are geopolitical rivals to the US and I don't see any sort of risk of anti-boycott regulations being applied in restricting business with residents of those countries. I guess you could say there is a risk that could change, but that seems hypothetical to the extreme and realistically irrelevant to worry about from a risk perspective.

And this isn't discriminating on nationality or national origin, it is on the nation you currently live in. Employers decide not to hire employees living in other countries all the time, it's the most prevalent choice (i.e. US companies only hiring employees living in the US). I don't see why doing this because a customer you've considered critical has asked for it is any more legally risky that having done it for other reasons, assuming we discount the anti-boycott argument.

This is all with the huge caveat of I'm not a lawyer, just giving my perspective based on how I've seen these laws/regulations applied in the past.