Just because something is a law does not mean that it is justified or morally correct. There have been many bad and unjustified laws on the books of the legal codes of many countries. Any means of carrying out the ends of a just law that will have terrible impacts are themselves also unjustified. When there are hundreds of people who have died in attempts to cross deserts or dangerous terrain to go around the fence in order to find gainful employment, that is a good indication that a policy is failing.