PHOENIX - The immigration debate in Arizona reached a boiling point in 2007 when the state passed a groundbreaking law targeting those often blamed with fueling the nation's border woes: employers who hire immigrants living in the U.S. illegally.

The law marked a bold step by a state into an area that had long been the domain of the federal government, and it paved the way for Arizona's landmark 2010 immigration law. It also represented a key moment in the immigration battles that continue today as Congress mulls a proposed overhaul of the immigration system.

But an examination of the law by The Associated Press found that it has done little to crack down on problematic employers. Only three of the state's 147,000 employers have been brought to civil court on illegal-hiring allegations, while several hundred employees who are living in the U.S. illegally have been arrested under a section of the law that made it a felony to use fake or stolen IDs to get jobs.

While the law has been upheld by the U.S. Supreme Court and hailed as a tool for states to confront illegal immigration, it has faced several problems:

• Hundreds of immigrant workers arrested under the law have spent months in jail on ID theft charges, while only two businesses - a sandwich shop and a now-defunct amusement park - had their business licenses suspended for several days. The case against the third business, a custom-furniture maker, is pending.

• A high legal standard for proving violations by businesses and a lack of subpoena power in getting employment records are almost insurmountable barriers to making cases against employers.

• Maricopa County Sheriff Joe Arpaio's office is the only police agency in the state that has raided businesses in enforcement of the employment law. It has arrested hundreds of workers in 72 business raids since 2008. The office has since been accused by the U.S. Justice Department of discriminating against Latino workers, allegations the sheriff denies.

• Despite the small number of cases against employers, the county prosecutor's office in metropolitan Phoenix has spent $4.5 million since 2008 investigating businesses suspected of hiring workers who aren't in the country legally and to pursue criminal ID theft cases against employees. Nearly a third of the money - $1.4 million - was given by the prosecutor's office to Arpaio's agency to investigate such cases.

Backers contend the enforcement numbers tell only a piece of the story. They say the law has helped combat identity theft and prompted immigrants living in the country illegally to leave Arizona. They also believe that the fear of business raids has caused employers to follow the rules.

"We are never going to get 100 percent compliance, but we have made a difference," said former Arizona Senate President Russell Pearce, the driving force behind the employment law and the state's 2010 immigration law that requires police officers, while enforcing other laws, to question people's immigration status if they are suspected of being in the country illegally.

The number of immigrants living in Arizona without permission to be in the U.S. declined by 200,000 from 2008 to January 2011, when the total estimated number stood at 360,000, according to a U.S. Department of Homeland Security report. While the law's backers say the decrease shows the state's immigration laws are working, other factors contributed to immigrants leaving the state, such as a construction industry that hemorrhaged jobs during that period.

Democratic state Sen. Steve Gallardo of Phoenix, an opponent of the law, said the imbalance in the number of cases against employers versus workers is a reflection of legislators who wanted to appear tough on illegal immigration but gave employers plenty of wiggle room.

"You have an employer-sanctions law that doesn't go after the employers," Gallardo said. "We should call it the employee-sanctions law."

More than 500 immigrants who weren't authorized to be in the country have been arrested on charges of using forged documents or stolen identities to get jobs at businesses raided by Arpaio's office since 2008. An unknown number of additional ID-theft arrests were made by other police agencies, which don't raid businesses in enforcing the law but make cases when people complain that their identity has been stolen.

"You have an employer-sanctions law that doesn't go after the employers. We should call it the employee-sanctions law."

Sen. Steve Gallardo, D-Phoenix