As expected, Obama's Federal Justice Department filed suit against Arizona for trying to aid in the enforcement of U.S. immigration laws through its own, recently-passed, but not yet implemented, legislation. In doing so, the Feds are basically telling Arizona, or any other state for that matter, that they are not responsible for enforcing a law that is "the" sole responsibility of the Federal government.
Well, if the states aren't responsible for assisting the Feds in the pursuit of any Federal violators -- such as illegal immigrants -- then, it is only logical, that the states completely ignore any outstanding Federal warrants or violators of any and all Federal laws. The Federal government cannot just pick and choose which laws they expect the states to assist them with and which ones they don't. In my opinion, to ignore some Federal violators while assisting in the prosecution of others is to ignore the "equal protection" clause of the United States Constitution.
The President, a trained Constitutional lawyer, should understand this. But, as usual Obama says screw the Constitution when any political gains are achievable!