Well, they can stay but they'd be downgraded to immigrant status. That means they can't complain about whatever system they're in or get deported if need be. Whatever the social justice issues are, it would be that respective country's burden.
uhhh so how "pure" does one need to be in order to be counted as a full person in your utopian society? jw since there are millions of Americans that would likely not be so easily labeled as either black or white.