PHOENIX A U.S. appeals court, in a ruling released on Monday, upheld a preliminary injunction against parts of Arizona's controversial immigration law that were challenged by the Obama administration.
Arizona's law included a provision that would require the police to determine the immigration status of a person they have detained and suspect is in the country illegally.
The 9th U.S. Circuit Court of Appeals ruled that a lower court did not abuse its authority by enjoining key sections of the state law, including the police requirement.
The law, which was signed by Republican Governor Jan Brewer at the end of April last year, had wide support in the Mexico border state and across the United States as a whole, but was opposed by President Barack Obama and civil rights groups.
Opponents of the law said it would lead to harassment of Hispanic Americans, and the Obama administration argued the U.S. Constitution gave the federal government sole authority over immigration matters.
The Republican-controlled Arizona legislature passed the measure to try to stem the flood of thousands of illegal immigrants who cross its border from Mexico and to cut down on drug trafficking and other crimes in the area.
U.S. District Court Judge Susan Bolton blocked the law's most controversial elements shortly before it was due to come into effect last July, arguing that immigration matters are the federal government's responsibility.
In addition to the requirement that police check immigration status, Bolton also had blocked a provision requiring immigrants to carry their papers at all times and made it illegal for people without proper documents to solicit for work in public places.
Brewer appealed the decision, arguing that the Obama administration had neglected its responsibility, and that Bolton had abused her discretion in blocking parts of the law, an argument dismissed by the appellate court on Monday.
"We hold that the district court did not abuse its discretion" by enjoining two key sections of the law, adding: "Therefore, we affirm the district court's preliminary injunction order enjoining these certain provisions."
Brewer's office did not have any immediate comment.
A Justice Department spokesman said: "We are pleased with the court's decision."
Immigration as an issue has festered in U.S. politics for years and attempts to overhaul the system have failed, most recently in 2007 when Republicans torpedoed reforms pushed by George W. Bush, then the Republican president.
The case in the 9th Circuit is United States of America v. State of Arizona, 10-16645.
(Reporting by Dan Levine; Additional reporting by Tim Gaynor; Editing by Eric Beech)