When Justice Antonin Scalia read aloud from his dissent in the Arizona immigration case on Monday, including an attack on President Obama’s recent decision not to deport many illegal immigrants who arrived here as children, it raised some eyebrows. Mr. Obama’s policy was announced two months after the case had been heard.

But Monday was a busy day at the Supreme Court, and Justice Scalia’s contention that the administration was refusing to enforce the nation’s immigration laws was only briefly noted as analysts pored over the meaning of his colleagues’ striking down of key elements of the Arizona law and their ruling on juvenile sentencing.

In the days since, however, the discussion has mushroomed. Commentators from across the political spectrum have been saying that Justice Scalia, who is the most senior as well as, hands down, the funniest, most acerbic and most politically incorrect of the justices, went too far.

“Illegal immigration is a campaign issue. It wouldn’t surprise me if Justice Scalia’s opinion were quoted in campaign ads,” Judge Richard A. Posner, a prominent federal appeals court judge, wrote Wednesday in the online journal Slate. Judge Posner, who sits on the United States Court of Appeals for the Seventh Circuit, in Chicago, is a famously conservative but also contrarian jurist who has criticized Justice Scalia’s focus on pure constitutional originalism as naïve and unrealistic.