In my opinion he's saying if immigration issues are going to be the exclusive duty of the Federal Government, refusing to address immigration issues should not be an option for the Feds.  In other words, they can't have their cake and eat it too.  And perhaps he's saying that by failing to address the issue, the Feds are in violation of their own constitutional obligations to the state of Arizona.  It would be similar to a scenario where a state gets invaded/attacked by a foreign country and the federal government refuses to defend the state against the attack.

I see the point he's making.  

Scalia is the number one right-wing hypocrite on the Supreme Court and the idol of the reactionary right. He pretends to preach strict textual construction and prattles on about judges not substituting their judgment for the legislature. He claims that text is everything and that judges should never get into intent, or even into history, to determine meaning. It's an enormous and transparent lie.

Scalia may be the least self-restrained most radical activist and politicized judge in the history of the Supreme Court. His diatribe today is just the latest example. It's a campaign speech of a political candidate masquerading as a judicial opinion. He rails against the evils of illegal immigration. He criticizes Congress for inadequate funding of immigation

enforcement as if, in the middle of enormous budget deficits, the Justices of the Supreme Court were the branch of government designated in the Constitution to decide where and how scarce funds should be spent. Then he criticizes the Executive Branch for inadequate enforcement of immigration laws, as if judges and justices were designated in the Constitution to be prosecutors as well as judges. Then he criticizes the President for a recent speech on deportation of aliens, a speech given after oral argument, about the legality of an executive order that is not at issue in the case.

His shameless citation of pre-Civil War states barring the entry of "certain classes of aliens" such as "freed blacks" and "indigents" as an example of state rights shows the true motive for most of his opinions - a glorification of discrimination against anyone that doesn't look like him ... and rationalization of whatever outcome is his personal preference ... under whatever rules of interpretation or construction he finds convenient at the time.

In this case, the target of his personal preference is Latino immigration. His rationalization today was not textual interpretation of the Constitution, but an ante-bellum view of "State Sovereignty" bolstered by his interpretation of history and his view of the intent of the founders. I guess he didn't remember that he's the guy who says that judges aren't supposed to look at intent or history. Had the target of the law been Italian immigrants, like his father and his grandparents on both sides, and the State involved been New Jersey, where he was born, or New York, where he grew up, he would have been the first to condemn it.

In addition, even in a profession known for arrogance and rudeness, he is incredibly rude, abusive and abrasive to those who appear before him. Horrible temperament for a justice and a miserable example for lower court judges. Disgraceful and despicable.

Not that I feel strongly about him.