This needs no analogy.
No matter the reason, what should be done is only people who actively want to assimilate to the native culture and population (and not assimilate the native population to their own, which is basically a invasion) if they want to permamently move here, through tests or some other means, should be allowed to immigrate. Those who just agree to respect local laws and culture a temporary stay, say for the remaining of the war. And those who don't, well, tough luck. You wouldn't take into your home a gangster just because he just was shot in a firefight, right?
