If Justice Antonin Scalia wasn't already the darling of immigration hardliners in Arizona and out, he made sure of it on Monday.

Scalia's dissent in Arizona v. U.S. made plain that he'll question the president's policy choices however he sees fit, even if they aren't directly part of a case before the court.

A majority that included Chief Justice John Roberts affirmed lower court decisions that said Congress, exercising its constitutional power, has preempted Arizona in key areas of immigration enforcement. Of four state law provisions at issue, the justices said three were improper and it was too soon to determine whether a fourth was invalid because it hasn't yet been enforced.

But Scalia, in his best finger-jab-in-the-chest style, extolled state sovereignty, harkening to the days when states could exclude "obnoxious aliens" at will. Of course, that was long before Congress passed comprehensive laws that basically occupy the field on such things as immigrant registration and deportation decisions, limiting what even frustrated states can do.

It's striking how stridently Scalia opposes the Obama administration's use of discretion in enforcing immigration law, dragging the president's recent policy announcement into a case that didn't directly involve it.

The justices certainly must have a sense of how their rulings affect the real world. But Scalia doesn't even pretend this is just about the law. His politics show too much.

He grouses that Arizona "bears the brunt of the country's illegal immigration problem," what with residents "under siege by large numbers of illegal immigrants who invade their property, strain their social services, and even place their lives in jeopardy," while federal officials are unable and unwilling to provide remedies.

But Scalia reaches far outside both the record and the arguments in the case to gripe about President Obama's announcement that immigration officials won't deport young people who were brought to the U.S. as children but have stayed in school and out of serious trouble.

"The husbanding of scarce resources can hardly be the justification for this," Scalia writes, even mentioning Obama's June 15 news conference and citing whitehouse.gov.

Scalia might have a valid argument, but it's based on his personal disagreement, not on legal justification.

He's quite alarmist in saying the federal government refuses to enforce the nation's immigration laws, thus leaving the states unprotected.

It surely surprised no one that Rush Limbaugh called Scalia's comments "right on the money." (bit.ly/Moc3QD)

What's more interesting is that Judge Richard Posner writes on slate.com that Scalia engaged in "fighting words" and made claims without backing them up. (slate.me/L1PKTR)

Posner's a Ronald Reagan appointee to the 7th U.S. Circuit Court of Appeals in Chicago and a longtime Republican icon, but he's no party mouthpiece.

Posner calls it a "defensible policy" to focus on catching and deporting criminals while leaving other immigrants alone if they're law-abiding aside from being in the country illegally. And the Supreme Court's ruling doesn't stop Arizona from helping to apprehend illegal immigrants who commit crimes, he notes.

Mind you, Posner's writing an online opinion piece, not a legal opinion in a case before him.

He says assertions about Arizona bearing the brunt from troublesome invaders are "sufficiently inflammatory to call for a citation to some reputable source of such hyperbole," but Scalia offers none.

Besides that, Posner says, the estimated 360,000 illegal immigrants in Arizona as of last year were less than 6 percent of the state's population, below the national average: "Maybe Arizona's illegal immigrants are more violent, less respectful of property, worse spongers off social services, and otherwise more obnoxious than the illegal immigrants in other states, but one would like to see some evidence of that."

Immigration is a highly emotional topic that evokes strong arguments from many sides.

But if Justice Scalia wants to fight with the president over policy decisions and how to deploy federal resources, maybe he should consider running for Congress. Arizona might elect him.