Strip them of their citizenship, and send them packing south of the border. Build a wall larger than the great wall of China and put an alligator moat on both sides. That ought to solve the problem. Any more gang members located on our side of the border toss them over as well.
PROBLEM SOLVED. As long as we are willing to put up with these people who call themselves human beings, they will be willing to congregate and cause us all grief.
(ok, they aren't all from Mexico, but most of them are).
Could always put a bounty on the strays once the invasion is stopped.