I really think that Arizona will prevail on this one. They aren’t usurping the federal government. They are merely assisting in the capture of illegal aliens that the government has failed miserably to do.
Feds to claim pre-emption in fight against AZ immigration-enforcement law
By Ed Morrissey
The Department of Justice will file a lawsuit this week, perhaps as early as today, against Arizona to block its new immigration-enforcement law. They plan to use the weakest argument possible, that of pre-emption, which amounts to a surrender on the grounds that the Obama administration has claimed in the previous three months of debate:
The Justice Department has decided to file suit against Arizona on the grounds that the state’s new immigration law illegally intrudes on federal prerogatives, law enforcement sources said Monday.
Truth, Lies and In Between 
Despite current claims by the Obama Administration to the contrary, the border is NOT more secure and resourced than it has ever been. Most Americans know nothing of the Punitive Expedition or the Mexican Border Campaign which occurred 94 years ago and involved more than 100,000 National Guard and Regular Army troops. This was the opening act for American involvement in the Great War and acted as the catalyst to transform our military into a modern force.
Here is a link to letters written by a National Guardsman on the Border exactly 94 years ago. Too bad our politicians are more interested in being politically correct than robustly defending the sovereignty of the United States.
http://worldwar1letters.wordpress.com/2008/06/29/rio-grande-el-paso-southwestern-rr-tunnel-7281916/