Lots of places have restrictions on immigration, especially on "economic" refugees. Moving isn't much of an option for them. And why should they have to leave?
And you didn't really answer my questions.
Your second comment is non sequitur, IMO. The issue isn't "overpopulation", its the fact that there's a large group of people who aren't going away. Any solution has to recognize that fact and deal with that fact in a constructive way.