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.

UPDATE: I respond to Ann Althouse’s comments in this post.