Obama has voiced his displeasure for the bill, and a court challenge either by the federal government or interest groups (or both) is likely. My thoughts are in line with Glenn Reynolds (see below). While not settled, it seems likely that the state is trampling on a federal issue. That said, the state's counter would be since the federal government is shirking on its responsibilities it is forced to act. Either way Arizona would win; the federal government reclaims its responsibilities or acknowledges that it will not giving the state free reign.
"ARIZONA’S IMMIGRATION BILL: I think that Krauthammer is right that it’s a response to the federal government’s failures, and I also agree with people who say it’s likely trumped by the Supremacy Clause — Congress has plenary authority over immigration, and though it’s not entirely settled — is there a “dormant immigration clause?” — that’s the way to bet. But it occurs to me in light of Krauthammer’s comments that there’s another clause in the Constitution that may be relevant: Article IV Section 4:
The United States shall guarantee to every State in this Union a Republican Form of Government, and shall protect each of them against Invasion; and on Application of the Legislature, or of the Executive (when the Legislature cannot be convened) against domestic Violence.
Were I representing Arizona, I’d argue that the federal government is in default on its “protection against invasion” responsibility, and that this empowers the state to resort to self-help. Not sure how that would play out, but it would make an interesting law review article. And a fun oral argument."
Video embedded below.