This was posted previously and I believe it may have some bearing on this question:
Federal Immigration and Nationality Act
Section 8 USC 1324(a)(1)(A)(iv)(b)(iii)
State and local law enforcement officials have the general power to investigate and arrest violators of federal immigration statutes without prior INS knowledge or approval, as long as they are authorized to do so by state law. There is no extant federal limitation on this authority. The 1996 immigration control legislation passed by Congress was intended to encourage states and local agencies to participate in the process of enforcing federal immigration laws. Immigration officers and local law enforcement officers may detain an individual for a brief warrantless interrogation where circumstances create a reasonable suspicion that the individual is illegally present in the U.S. Specific facts constituting a reasonable suspicion include evasive, nervous, or erratic behavior; dress or speech indicating foreign citizenship; and presence in an area known to contain a concentration of illegal aliens.
http://www.freerepublic.com/focus/bloggers/2501530/posts
However, the problem is that this isn't really primarily a legal issue at all, and all the major players know it perfectly well. It's political warfare, aka "lawfare" by the federal government for the purpose of subjugating the states, aided by continuous propaganda warfare from the media. As such there are additional dimensions to the efforts of the state of Arizona which are needed in order to counter this offensive.
The state must of course continue the traditional legal defense through the courts, but if they do only that it will play into the Obama regime's hands by allowing the public discussion to be "quieted down" and enable the media to focus the public's attention elsewhere. This benefits Obama's agenda.
What is also needed from Governor Brewer and her spokesmen and supporters is a full-out media blitz of Alinsky-style ridicule of the lawsuit. For example, when the argument of encroachment on federal jurisdiction is finally presented, she could issue a statement to the effect that "the Attorney General says that Arizona has no suthority to enforce federal immigration statutes. Well, I have a question for Mr Holder. Bank robbery is also a federal crime. If a bank is being robbed and calls the state or local police for help, should we just tell them to call the FBI?".
This may seem silly or undignified, etc. etc., but it works, and the left has been using it for decades with devastating effectiveness against us. Their arguments, and they themselves personally, need to be publicly scorned and ridiculed mercilessly. It's time to the tables on them, and they provide a truly target rich environment. As Alinsky taught, pick the target, freeze it, personalize it and ridicule it.