Philippe Legrain says,

Illegal immigrants are not the problem, they are the symptom of the real problem: immigration restrictions that are economically stupid, politically unsustainable and morally wrong. Far from protecting society, immigration controls undermine law and order, just as Prohibition did more damage to America than drinking ever has.

What I wrote in Order and Disorder would suggest that we would have more order if we were to use taxes rather than restrictions to limit immigration. Charge guest workers or immigrants a large fee, and eventually we will have order at the border.