Ok, here's the plain old text of section 264 of the US Immigration and Nationality Act federal law: http://www.uscis.gov/ilink/docView/S...-0-0-8289.html

So I agree, this says legally residing aliens should carry their papers with them "at all times."

Here's Arizona fact sheet on SB1070: http://www.azleg.gov/legtext/49leg/2...70pshs.doc.htm
Here's the full text: http://docs.google.com/viewer?a=v&q=...zuviOXyQ1ZxvVQ

The piece of which that most certainly is not already a federal law is,

"For any lawful contact made by a law enforcement official…where reasonable suspicion exists that the person is an alien who is unlawfully present in the United States, a reasonable attempt shall be made…to determine the immigration status of the person."

Some scanning through the Justia brief on reasonable suspicion led me to a supreme court decision United States v. Brignoni-Ponce, 422 U.S. 873 (1975) that sure seems to be counter to the above provision of Arizona SB 1070. It states:

"The Fourth Amendment held not to allow a roving patrol of the Border Patrol to stop a vehicle near the Mexican border and question its occupants about their citizenship and immigration status, when the only ground for suspicion is that the occupants appear to be of Mexican ancestry. Except at the border and its functional equivalents, patrolling officers may stop vehicles only if they are aware of specific articulable facts, together with rational inferences therefrom, reasonably warranting suspicion that the vehicles contain aliens who may be illegally in the country."

What sort of "specific articulable facts" could there be that provide some kind of distinction between a hispanic citizen/legal resident, and an illegal? Both looking Mexican AND speaking Spanish? Ordering a taco? Going to a Los Lonely Boys concert? Wearing a Cholula hot sauce trucker hat? Standing in front of Home Depot offering to do roofing for cheap? Stuffing 7 people into a brown 1985 Nissan Maxima with bubbling purple window tint, saggy rear shocks and a gothic-script RODRIGUEZ banner across the rear window?

So no, it's not about having sympathy for illegals or not wanting to round them up. It's about thinking this leaves the door way too freakin wide open for a large number of citizens and legal residents to be under constant scrutiny by the cops.