Argument: Cops will trump up charges in order to find illegals
Shikha Dalmia. "Arizona's Law: Anti-Immigrant And Anti-Constitutional." Forbes. April 5th, 2010: "The amended law limits such inquiries to instances when cops make a lawful stop, detention or arrest in the course of enforcing some other law or local ordinance. But including local ordinances as grounds for an immigration inquiry opens all kinds of tantalizing harassment possibilities for officials like Joe Arpaio--the notorious but popular Arizona sheriff who has made it his personal mission to root out undocumented aliens from the state by launching crime sweeps in Latino communities on the flimsiest of pretexts.
Under the new law, Arpaio could troll Hispanic neighborhoods demanding the papers of anyone breaking, say, a local pooper-scooper law while walking their dogs. If they can't comply on the spot, he could haul them to a police station while their immigration status is checked. If it turns out that they are here illegally, they could be arrested, pending deportation. This means that the same pooper-scooper violation that would produce nothing more than a small fine for unaccented white folks--since they would not raise any “reasonable suspicion” that would justify an inquiry into their immigration status--could well result in a lengthy police encounter for Hispanic citizens or Hispanics with valid visas--and deportation for anyone who had overstayed their visa by even a day. 'If this doesn't raise equal protection and Fourth Amendment concerns then what does?' asks Cecillia Wang, an attorney with the American Civil Liberties Union."