"I remain steadfast in my belief that Arizona and other states have a sovereign right and obligation to protect their citizens and enforce immigration law in accordance with federal statute," Brewer said in a statement with state Attorney General Tom Horne.
A three-judge panel of the 9th U.S. Court of Appeals in San Francisco Monday upheld a lower court ruling that barred the most controversial provisions of the law from taking effect.
Those provisions include calling for officers to check a person's immigration status while enforcing other laws and requiring immigrants to carry their papers at all times.
"By imposing mandatory obligations on state and local officers, Arizona interferes with the federal government's authority to implement its priorities and strategies in law enforcement, turning Arizona officers into state-directed [Department of Homeland Security] agents," the appellate panel said in an opinion written by Judge Richard A. Paez, appointed by President Bill Clinton.
The provisions are an attempt to "hijack" congressional intent and "usurp the [U.S.] attorney general's role in directing state enforcement of federal immigration laws," the opinion said.
A concurring opinion by Judge John T. Noonan Jr., appointed by President Ronald Reagan, said "foreign policy is not and cannot be determined" by individual states.
Letting individual states "have a foreign policy is absurdity too gross to be entertained," he said. "In matters affecting the intercourse of the federal nation with other nations, the federal nation must speak with one voice."
Judge Carlos T. Bea, appointed by President George W. Bush, dissented from parts of the ruling.
Brewer, a Republican who supports the crackdown on immigrants, said Arizona might file an immediate petition to the U.S. Supreme Court to lift the lower court injunction, ordered July 28, 2010, a day before the law, known locally as Senate Bill 1070, was to take effect.
"I believe the 9th Circuit decision will be overturned by the United States Supreme Court, and I pledge to make every possible effort to achieve that result," Horne said.
Arizona may also appeal Monday's decision to the full 9th Circuit or go back to U.S. District Judge Susan Bolton in Phoenix for a trial to determine if permanently blocking the law is unconstitutional.
Bolton continues to oversee challenges to the law.
The law was enacted in April 2010 after Arizona officials argued they needed their own immigration law to keep illegal immigrants out of the state. Federal efforts were not enough, they argued.
The law -- which coincided with economic anxiety and a number of high-profile crimes attributed to illegal immigrants -- sparked boycotts and protests across the nation. Activists accused Arizona of trying to take over the federal government's job to define immigration rules. They also accused Arizona of proposing unconstitutional actions, such as profiling.
The U.S. Justice Department sued to block the law from going into effect. It argued the federal government had the responsibility for immigration law, not Arizona.
Several other states, including Georgia and Alabama, are considering similar laws. Mississippi and Kansas weakened or abandoned tough bills to avoid the litigation and protests that Arizona faced, The New York Times reported.
Utah voted for a milder enforcement bill after lawmakers concluded Arizona would likely lose the Justice Department's challenge. Utah also created a guest-worker program for illegal immigrants.