Gov. Jan Brewer of Arizona and her team of lawyers defended the state’s strict new immigration law in a federal appeals court on Monday, facing a panel of three judges who sharply questioned the way the law would be carried out. Lawyers from the Justice Department argued that central parts of the state law were unconstitutional and would interfere with federal law enforcement.
In July, just one day before the law was to take effect, a lower court suspended parts of it, ruling that the state could not require local law enforcement officials to check on the immigration status of people they stop and detain them if they were suspected of entering the country illegally.
Ms. Brewer is appealing that decision. Whatever the outcome from the United States Court of Appeals for the Ninth Circuit here, it, too, is expected to be appealed, and Ms. Brewer has said she will take it to the Supreme Court if necessary.
During Monday’s hearing, the appellate judges abruptly ended a discussion of a provision of the state law that would forbid illegal immigrants to work in the state, saying that a decision in another case had already blocked the state from making it a crime for such immigrants to seek employment.
The judges focused on the central question of whether a state could take it upon itself to enforce federal laws.
“If I don’t pay my income tax to the federal government, can California come along and sue me?” asked Judge Carlos T. Bea.
John J. Bouma, the lawyer for Arizona, responded, “I don’t think California would be particularly interested.”
The panel also grappled with whether police officers were free to question the people they stop about crimes beyond the grounds for the stop. The judges pointedly asked lawyers for the Justice Department whether the practice should never be allowed. The Obama administration has said that requiring police officers to question immigration status is unconstitutional and could damage relationships with other countries, making American citizens abroad more vulnerable to unfair treatment.
At one point in the hearing, Judge Richard A. Paez and Mr. Bouma sparred over parsing of the law.
“The statute says ‘shall’ check the immigration status,” Judge Paez said.
“We encourage them to do it,” Mr. Bouma replied.
“That’s a generous interpretation of the word ‘shall,’ ” Judge Paez responded, one of several times the judges drew laughs from the packed courtroom.
Judge John T. Noonan Jr. pressed Edwin S. Kneedler, the deputy solicitor general representing the Justice Department, on why such a requirement was unconstitutional.
“I don’t understand your argument,” Judge Noonan said, adding that such a requirement did not necessarily usurp federal law. “I would think the proper thing to do is to concede that this is a point where you don’t have an argument.”
The judges suggested they might agree that requiring immigrants to carry citizenship papers would conflict with federal policy, telling the lawyers not to spend time discussing that part of the law during the one-hour hearing.
The judges appeared more vexed by a provision that would allow local officers to hold suspects until their immigration status could be determined.
“How long would that be?” Judge Paez asked. “Twenty-four hours? Forty-eight hours? A week?”
Mr. Bouma said federal immigration officials typically got back to local officers within 11 minutes.
The law, which passed the Arizona Legislature in April, has ignited controversy across the country and forced politicians running in the midterm elections to take a stand on it. Emotions also ran high Monday outside the courthouse, where dozens of protesters from both sides stood for hours. A few opponents of the law wore T-shirts that read “Don’t militarize the state” while those supporting the law held signs proclaiming “Stop the invasion.”
Governor Brewer, a Republican who is comfortably ahead in her bid for re-election according to polls, said Monday that she had appeared in court “on behalf of the people of Arizona,” and that officials in other states were moving to enact similar laws.
“We would not be here today if the federal government had done their job,” she told reporters after the hearing. “We are not their enemy — we are part of the United States of America.”
Mr. Kneedler said such a “patchwork of laws” was precisely what the government wanted to avoid and argued that immigration was solely under federal jurisdiction.
“This has to be considered in the light of what would happen if every state in the nation did this,” Mr. Kneedler said.
In September, the United States Court of Appeals for the Third Circuit ruled that an ordinance in Hazleton, Pa., undermined the federal government’s control over immigration. That measure would have fined landlords who rented to illegal immigrants and penalized businesses that hired them.