The law requires that law enforcement officers engage din a lawful stop must, when practicable, ask about a person's legal status, if there is a reasonable suspicion that the person is in the U.S. illegally*. The law already has been challenged in four other suits, but this appears to be the most comprehensive effort. The Justice Department has also said it is considering challenging the law, which is set to go into effect in late July.
But all of those efforts could be complicated by a 2002 memo which opined that state police officers have "inherent power" to arrest undocumented immigrants for violating federal law. The Arizona legislator behind the new law, Republican Russell Pearce, has said cited the memo as offering support for the legislation.
The memo was written by Jay Bybee, the former head of DOJ's Office Of Legal Counsel, who also authored some of the controversial "torture memos" in which the Justice Department signed off on the use of harsh interrogation techniques against detainees. In 2003, Bybee was appointed by President Bush to a federal judgeship.
The memo about undocumented immigrants has not been withdrawn by the Obama administration. It was released publicly, though in redacted form, in 2005, after civil rights groups sued to obtain it.
Bob Driscoll, a former Bush Justice Department lawyer now working with Sheriff Joe Arpaio, summed up the case that supporters of the law likely will make. "The Justice Department's official position as of now is that local law enforcement has the inherent authority to enforce federal immigration law," Driscoll told the Washington Post. "How can you blame someone for exercising authority that the department says they have?"
But an ACLU lawyer said the law at issue "goes far beyond" the arrest authority laid out in the memo.
* This sentence has been corrected from an earlier version.