Brought it up to show how they can get around needing to have them already stopped for something else.
The police can't legally get around having to stop a person for some legitimate reason before starting the investigation into residence status.
In the thread concerning the burned-out tag light, the driver was stopped legally, at least according to the cop. But if the light was working and the cop just used that excuse to pull over the driver, then the cop is in violation of the law and everything that happens after that will be inadmissable in court. You know this already, I'd bet.
Will Arizona's new law stop police corruption/crime/illegal stops? No, of course not. All it does is allow the police to investigate a person's US residence status once a "lawful" stop has been made. I saw " lawful" because only the courts can decide after-the-fact if the stop was lawful.
Will there be cops unlawfully stopping/detaining "brown people" just to check their immigration status? Yes, of course. Do we currently have cops that unlawfully stop people to check for seatbelt useage, drunk driving, insurance, drugs, etc? Yes, of course.
Will the new AZ law create thousands of rogue cops who just want to detain/harass/deport "those brown people?" I don't think so.