I think the judge is being sarcastic here.
If AZ police stops a dark skin person and discover he is illegal and then call the Feds and they do nothing about the illegal then this after a time will prove to be pointless. Why then should AZ police bother checking if the Feds are going to let an illegal go free? If AZ police persist in doing this the Feds will say in not so many words "If you know we won't do anything why are you doing this? Is it because you Arizonans are raceist?"
AZ police will stop checking illegals, because they don't want to go to court or be accused of being raceist.