PHOENIX – A federal appeals court Monday refused to lift a stay blocking major parts of Arizona’s immigration law from taking effect and said the federal government is likely to be able to prove the controversial law is unconstitutional.

The 9th U.S. Circuit Court of Appeals turned down an appeal filed by Republican Gov. Jan Brewer. She had asked the appeals court to lift an injunction imposed by a federal judge in Phoenix the day before the law was to take effect July 29, 2010.

The U.S. Justice Department sued to block the law, saying it violates the U.S. Constitution because enforcing immigration law is a federal issue.

U.S. District Court Judge Susan Bolton issued an injunction preventing four major parts of the law from going into effect pending a trial. Monday’s ruling by the three-judge appeals court panel upheld that injunction.

The panel’s opinion said the government is likely to succeed in its arguments that Congress has given the federal government sole authority to enforce immigration laws, and that Arizona’s law violates the Supremacy Clause of the Constitution. One judge dissented.

Brewer’s lawyers said the federal government hasn’t effectively enforced immigration law and that the state law will assist federal authorities.

“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.

The governor’s office said Brewer, Arizona Attorney General Tom Horne and their legal team — in conjunction with counsel for the Arizona Legislature — will be considering their legal options, including appealing to a larger 9th Circuit panel or seeking an immediate petition for the U.S. Supreme Court, to lift the injunction.

Parts of the law blocked from taking effect while the case works its way through the courts include a provision requiring police to question people’s immigration status while enforcing other laws if there is a reasonable suspicion they’re in the country illegally.

Other provisions that are on hold include: requiring all immigrants to obtain or carry immigration registration papers; making it a state criminal offense for an illegal immigrant to seek work or hold a job; and allowing police to arrest suspected illegal immigrants without a warrant.

In a separate opinion concurring with the panel’s ruling, Appeals Court Judge John T. Noonan noted the intent of the state statute is clear and goes beyond what federal law allows.

“If we read Section 1 of the statute, the statute states the purpose of providing a solution to illegal immigration in the United States. So read, the statute is a singular entry into the foreign policy of the United States by a single state,” he wrote.

Judge Carlos Bea would uphold two of the provisions — those allowing police to question people about their immigration status and to make warrantless arrests — and wrote a pointed dissent.

“As I see it, Congress has clearly expressed its intention that state officials should assist federal officials in checking the immigration status of aliens,” he wrote.