See, this is precisely the kind of thing I want clarified.
In the US, it is illegal to buy replicas from China. You're smuggling counterfeit goods, without forgetting that you're avoiding the tax/duty. If it were legal, Customs wouldn't stop the packages; they'd just ask for the unpaid tax and send you your watch.
Selling to an acquaintance is 100% illegal, so it's hardly a grey area. Sure, you're not going to get huckled up before the beak for it, but that doesn't mean it's a grey area.