Statistics obtained by The Associated Press show that the Maricopa County Sheriff's Office was responsible for deportations or forced departure of 26,146 immigrants since 2007.
That's about a quarter of the national total of 115,841 sent out of the U.S. by officers in 64 law enforcement agencies deputized to help enforce immigration laws, some since 2006, under the so-called 287(g) program.
The tens of thousands of immigrant arrests show local officials already have a significant amount of authority to enforce immigration laws and help remove illegal immigrants from the country.
But with Maricopa County Sheriff Joe Arpaio the top law officer among all those deputized, questions remain about what's in store when Arizona gives more officers the power to enforce immigration laws. The federal government already is under fire for doing a poor job of keeping watch on local officers enforcing immigration laws and ensuring safeguards for protecting civil rights are in place.
Arpaio is under federal investigation on allegations of civil rights allegations, which he denies.
If Arizona's new law takes effect Thursday, many more of the state's officers will be asking people to prove they are legally in the U.S. The state law requires officers to ask for a driver's license, passport or other identity document if they reasonably suspect a person is not allowed to be in the U.S. They must do so while enforcing other laws or ordinances.
The federal government is trying to block the Arizona law, arguing it usurps its authority. The Justice Department said in its suit challenging the law that the 287(g) federal-local partnerships are one way Congress allowed states to assist in enforcing immigration laws.
"At the pragmatic level, if local police are already allowed to do this and are allowed to do this with federal cooperation with the state, then why do they need the (new Arizona) law?" said Muzaffar Chishti, director of the New York office of the Migration Policy Institute, an immigration think tank.
There are several other ways local officials can assist, including Secure Communities, a more widely used program that allows local officials to check the fingerprints of anyone they book into their jails against FBI and Homeland Security Department databases.
But the 287(g) program gives officers the most direct authority to stop people on the street, in their cars or in their communities and check whether they are in the country illegally. Federal watchdogs have been critical of the job the Homeland Security Department has been doing in running the program.
The department's inspector general reported in March that the 287(g) program was poorly supervised and provided insufficient training to officers, including on civil rights law.
Local officers have operated outside their agreements dictating the limits of their authority, the report said. In all, the inspector general made 33 recommendations for overhauling the program, some of which have not yet been resolved. It was the second critical report for the program. The Government Accountability Office had criticized the program in July 2009.
Complaints about Arpaio's immigration enforcement tactics led the federal government last October to yank his authority to enforce immigration laws during patrols. That month, the Obama administration rewrote all agreements with local partners in attempt to address complaints of racial profiling and civil rights violations.
Even so, the federal government continues to allow the sheriff and deputies to check their jails for deportable inmates.
Arpaio has denied the allegations and says he is a target because of his tough immigration enforcement. His office has continued to do immigration sweeps. Arpaio said he is enforcing state anti-smuggling and anti-illegal immigrant hiring laws.
Arpaio said about 100 of his deputies were trained over five weeks to act as federal agents under the 287(g) program. They were trained on racial profiling and other civil rights laws, he said.
The new Arizona law is needed for several reasons, including that "no police official or elected official can tell the police officer that you cannot enforce immigration laws," Arpaio said. The Arizona law prohibits state and local government officials from preventing enforcement of immigration laws.
The federal government does not pay for local officers to participate in the 287(g) program. U.S. taxpayers pay the federal cost, which has grown from $5 million in 2006 to $68 million in 2010, according to the DHS inspector general. Immigration and Customs Enforcement reimburses some of the local agencies for housing immigrants in their jails. The immigrants can be in the country illegally or legally present but have committed a crime that makes them eligible for deportation.
Joanne Lin, legislative counsel for the American Civil Liberties Union, said it is alarming that one Arizona county is responsible for a disproportionate share of deportations.
The Los Angeles County's Sheriff's Office, a distant second to Maricopa, helped find 13,784 immigrants who were later deported or left the country. The Sheriff's Office's agreement with the federal government allows it to check its jails for deportable immigrants, but not to enforce immigration laws during street patrols. A renewal of the agreement is under negotiation.
An estimated 10.8 million people, about 26 percent of the state's population, are living illegally in California, compared with 460,000, about 12 percent, in Arizona.
"These statistics bear out that you have rogue sheriffs in certain counties that are bent on targeting immigrants," Lin said.
Immigration and Customs Enforcement, 287(g): http://www.ice.gov/pi/news/factsheets/section287_g.htm