The U.S. Supreme Court’s first Hispanic justice took a lead role in criticizing oral arguments over Arizona’s controversial immigration law.

The liberal Sotomayor, President Barack Obama's first Supreme Court appointee, was most widely quoted for her stinging criticism of the government’s argument that Arizona’s law preempts federal authority over immigration.

But her lines of questioning and criticism of Arizona’s rebuttal also indicated skepticism about the most contentious provisions of the state law.

“You are involving the federal government in your prosecution,” the justice said, according to the hearing’s transcript, drawing attention to one class of non-citizens who may not appear in available databases of documented residents.  

The questions Sotomayor posed to Paul Clement, the attorney representing Arizona, hinged on what would happen to people detained under SB 1070, as the law is known, who did not readily appear in databases. She noted that some people, like political asylum applicants, may not be registered with the federal government because the process requires them to keep their status private.

“What’s going to happen now is that if there is no statement by the federal agency of legality, the person is arrested, and now we’re going to have federal resources spent on trying to figure out whether they have that, whether they are exempted for this reason, whether the failure to carry was accidental or not,” Sotomayor said.

Sotomayor was the only justice to pose questions during Clement’s rebuttal.  

The Latina justice also jumped in with the first line of questioning, parsing out how detention processes under suspended provisions of the Arizona law would differ from current practice, and she posed questions highlighting the limitations of current federal databases to check people’s immigration status efficiently after being stopped.

There is no federal database of authorized residents, only a passport registry, according to U.S. Solicitor General Donald Verrilli, who is arguing on behalf of the Obama administration. The federal government also checks reports of undocumented immigrants against another eight to10 federal databases, Verrilli said.

Hypothetically, then, under the Arizona law a person stopped for an offense and held on suspicion of unlawful residence could wind up in custody for long periods of time, Sotomayor posited.

While Sotomayor’s line of questioning indicated skepticism of parts of Arizona’s case, it was her biting criticism of Verrilli’s argument that Arizona’s enforcement of immigration undermined federal authority that caught the most attention.

“You can see it’s not selling very well,” Sotomayor said, commenting on a series of both tough questions and outright assertions made by the country's highest court, where conservatives hold a majority.

“Arizona is not trying to kick out anybody that the federal government has not already said do not belong here,” said Justice Antonin Scalia.

The most forceful argument in favor of the controversial immigration law’s provision requiring police to check the immigration status of those they stop came from Chief Justice Roberts.

“It is still your decision,” Roberts told Verrilli. “And if you don’t want to know who is in this country illegally, you don’t have to.”

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