A federal judge dealt a serious blow to Arizona's toughest-in-the-nation immigration law on Wednesday when she put most of the crackdown on hold just hours before it was to take effect.
The ruling by U.S. District Judge Susan Bolton sets up a lengthy legal battle that may not be decided until the Supreme Court weighs in.
Read Judge Bolton's Decision
The Obama administration, one of the litigants in the case, opposes the state legislation on grounds it usurps federal authority over immigration policy.
Paul Senseman, a spokesman for Republican Gov. Jan Brewer, said the state will appeal Bolton's ruling to the 9th U.S. Circuit Court of Appeals in San Francisco on Thursday, asking the appellate court to lift the injunction and allow the blocked provisions to take effect. The appeal will ask the 9th Circuit to act quickly, Senseman said.
Whatever way that court rules, Bolton will eventually hold a trial and issue a final ruling.
The White House had no comment on the ruling.
Brewer said in a statement, "This fight is far from over. In fact, it is just the beginning, and at the end of what is certain to be a long legal struggle, Arizona will prevail in its right to protect our citizens. I am deeply grateful for the overwhelmingly support we have received from across our nation in our efforts to defend against the failures of the federal government.
For now, opponents of the law have prevailed: The provisions that most angered opponents will not take effect, including sections that required officers to check a person's immigration status while enforcing other laws.
For those who have been demonstrating against Arizona's new immigration law the preliminary injunction blocking its most controversial sections was a relief after weeks of worry. It seemed an answer to their prayers, reports CBS News correspondent John Blackstone.
But most of the people of Arizona - 65 per cent according to a recent poll - support the new law. This is a state where it's estimated 460,000 illegal immigrants are now living, reports Blackstone.
The judge also delayed parts of the law that required immigrants to carry their papers at all times and made it illegal for undocumented workers to solicit employment in public places - a move aimed at day laborers. In addition, the judge blocked officers from making warrantless arrests of suspected illegal immigrants.
"Requiring Arizona law enforcement officials and agencies to determine the immigration status of every person who is arrested burdens lawfully present aliens because their liberty will be restricted while their status is checked," Bolton said in her decision.
Bolton said the controversial sections should be put on hold until the courts resolve the issues. Other provisions of the law, many of them slight revisions to existing Arizona immigration statute, will go into effect at 12:01 a.m. Thursday.
The law was signed by Brewer in April and immediately revived the national debate on immigration, making it a hot-button issue in the midterm elections. The law has inspired similar action elsewhere, prompted a boycott against Arizona and led an unknown number of illegal immigrants to leave the state.
Lawyers for the state contend the law was a constitutionally sound attempt by Arizona to assist federal immigration agents and lessen border woes such as the heavy costs for educating, jailing and providing health care for illegal immigrants. Arizona is the busiest gateway into the country for illegal immigrants, and the state's border with Mexico is awash in drugs and smugglers that authorities badly want to stop.
"It's a temporary bump in the road, we will move forward, and I'm sure that after consultation with our counsel we will appeal," Brewer told The Associated Press. "The bottom line is we've known all along that it is the responsibility of the feds and they haven't done their job so we were going to help them do that."
The ruling came just as police were making last-minute preparations to begin enforcement of the law and protesters were planning large demonstrations against the measure. At least one group planned to block access to federal offices, daring officers to ask them about their immigration status.
In a sign of the international interest in the law, about 100 protesters in Mexico City who had gathered in front of the U.S. Embassy broke into cheers when speakers told them about the federal judge's ruling. The demonstrators had been monitoring the news on a laptop computer on the stage.
The crowd clapped and started chanting, "Migrants, hang on, the people are rising up!"
Gisela and Eduardo Diaz went to the Mexican consulate in Phoenix on Wednesday seeking advice because they were worried about what would happen to their 3-year-old granddaughter if they were pulled over by police and taken to a detention center.
"I knew the judge would say that part of the law was just not right," said Diaz, a 50-year-old from Mexico City who came to Arizona on a since-expired tourist visa in 1989. "It's the part we were worried about. This is a big relief for us."
Opponents argued the law would lead to racial profiling, conflict with federal immigration law and distract local police from fighting more serious crimes. The U.S. Justice Department, civil rights groups and a Phoenix police officer had asked the judge for an injunction to prevent the law from being enforced.
"There is a substantial likelihood that officers will wrongfully arrest legal resident aliens under the new (law)," Bolton ruled.
Federal authorities have argued that letting the Arizona law stand would create a patchwork of immigration laws nationwide that would needlessly complicate the foreign relations. Federal lawyers said the law is disrupting U.S. relations with Mexico and other countries and would burden the agency that responds to immigration-status inquiries.
The core of the government's case is that federal immigration law trumps state law - an issue known as "pre-emption" in legal circles.
The judge pointed out five portions of the law where she believed the federal government would likely succeed on its claims that U.S. law supersedes state law.
Responding to the ruling, Justice Department spokeswoman Hannah August said that the agency understands the frustration of Arizona residents with the immigration system. She added that a wide range of state and local policies would seriously disrupt federal immigration enforcement.
Brewer's lawyers said Arizona shouldn't have to suffer from America's broken immigration system when it has 15,000 police officers who can arrest illegal immigrants.
Brewer is running for another term in November and has seen her political fortunes rise because of the law's popularity among conservatives. It's not yet clear how the ruling will affect her campaign, but her opponent was quick to pounce.
"Jan Brewer played politics with immigration, and she lost," Arizona Attorney General Terry Goddard, a Democrat. "It is time to look beyond election year grandstanding and begin to repair the damage to Arizona's image and economy."
Republican Rep. John Kavanagh, one of the law's top supporters, said he was disappointed by the ruling and that he expects it to ultimately end up being decided by the U.S. Supreme Court.
"I don't think the judge's statements in the hearings justify this ruling," Kavanagh said. "I don't think the law justified her injunction."
"Even though Arizona's interests may be consistent with those of the federal government, it is not in the public interest for Arizona to enforce pre-empted laws," Bolton wrote.
Rep. Ann Kirkpatrick, a Democrat, released a statement in which she said, "The courts may have ruled in favor of the federal government today, but the legal wrangling is just beginning. We have months and months of courtroom battles ahead of us, and Arizona's taxpayers are being forced to fund both sides - that is money that should be going towards protecting our communities."
Meanwhile, one Arizona county has without SB 1070, the law that will go into effect in a slightly different form after Judge Bolton's Wednesday ruling.
More on Arizona's Immigration Law:
Tension Builds As Arizona Immigration Law Looms
Ariz. Gov. Seeks Dismissal of Immigration Suit
Neo-Nazi Group Patrolling U.S. Border
Is Political Rhetoric Hurting Ariz. Tourism?