People come down on one side or the other of the illegal immigration argument for various reason. The argument put forth by the administration is incomprehensible. They say they want a single approach for the entire country and their approach has been to basically ignore illegal immigration. The Bush administration was pretty much the same way.The Obama administration, which opposes those measures, has argued that the country cannot sustain a patchwork of separate immigration laws. Verrilli, who is arguing on behalf of the government, said in his brief that the Executive Branch has the power to enforce immigration policy. "For each state, and each locality, to set its own immigration policy in that fashion would wholly subvert Congress' goal: a single, national approach," he wrote.
Illegal immigration is expensive for the states due to the crimes committed by some illegal immigrants, educational expenses, medical care, etc. The total amounts go into the tens of billions and possibly more. If the federal government is ignoring illegal immigration, the states will step forward with their own approach out of financial necessity. Ignoring a problem is not a proper "single, national approach".