Posner, as you may know, is generally regarded even by people who disagree with him often as one of America's great legal thinkers.  He was appointed to the 7th Circuit Court of Appeals by none other than Ronald Reagan shortly thereafter, and has been there ever since, where he has usually enlightened and sometimes maddened just about everybody with his frequent public writings.  So his views are not to be trifled with.

Read the whole thing in Salon.  Here's some key points:

Justice Scalia is famously outspoken. Is that a good thing for a Supreme Court justice to be? Good or bad, it seems correlated with an increasing tendency of justices to engage in celebrity-type extrajudicial activities, such as presiding at mock trials of fictional and historical figures (was Hamlet temporarily insane when he killed Polonius? Should George Custer be posthumously court-martialed for blowing the Battle of the Little Big Horn?). My own view, expressed much better by professor Lawrence Douglas of Amherst, is that such activities give a mistaken impression of what trials are good for. But I would give Justice Sotomayor a pass for appearing on Sesame Street to adjudicate a dispute between two stuffed animals.

But that is to one side of Justice Scalia's opinion.

He is very concerned with the fact that the Obama administration recently announced a program suspending deportation efforts directed at more than1 million illegal immigrants under the age of 30. He quotes President Obama as having said that the program was "the right thing to do." Justice Scalia says that it "boggles the mind" to think that Arizona could be contradicting federal law by enforcing applications of federal immigration law "that the President declines to enforce." He says that the federal government "does not want to enforce the immigration laws as written, and leaves the States' borders unprotected against immigrants whom those laws would exclude." The federal government is "refus[ing] to enforce the Nation's immigration laws."

These are fighting words. The nation is in the midst of a hard-fought presidential election campaign; the outcome is in doubt. Illegal immigration is a campaign issue. It wouldn't surprise me if Justice Scalia's opinion were quoted in campaign ads. The program that appalls Justice Scalia was announced almost two months after the oral argument in the Arizona case. It seems rather a belated development to figure in an opinion in the case.

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In his peroration, Justice Scalia says that "Arizona bears the brunt of the country's illegal immigration problem. Its citizens feel themselves under siege by large numbers of illegal immigrant who invade their property, strain their social services, and even place their lives in jeopardy." Arizona bears the brunt? Arizona is only one of the states that border Mexico, and if it succeeds in excluding illegal immigrants, these other states will bear the brunt, so it is unclear what the net gain to society would have been from Arizona's efforts, now partially invalidated by the Supreme Court. But the suggestion that illegal immigrants in Arizona are invading Americans' property, straining their social services, and even placing their lives in jeopardy is sufficiently inflammatory to call for a citation to some reputable source of such hyperbole. Justice Scalia cites nothing to support it.