Did they stop people at the border before letting them in?
It makes a huge difference that they weren't welcomed with open arms. Most of the ones who are there really wanted to be there. It's not hard to weed out the trash if you don't welcome it in and pour free money into their pockets.
I am speaking of the life of a man who knows that the world is not given by his fathers, but borrowed from his children; who has undertaken to cherish it and do it no damage, not because he is duty-bound, but because he loves the world and loves his children… - Wendell Berry, 1971