Two local law enforcement agencies have launched special units devoted to fighting migrant smuggling, an unusual move given that immigration has long been the province of the federal government.

The squads in the Maricopa County Attorney's and Sheriff's offices were set up, in part, to enforce a new law that creates the state crime of human smuggling. The law, which takes effect Aug. 12, was borne of the frustrations many felt that the federal government wasn't doing enough to confront illegal border-crossings.

Some politicians insisted that Arizona (search), the nation's busiest illegal immigration corridor, must do what it can to lessen the problem.

Maricopa County Sheriff Joe Arpaio (search) said his six-person unit will only target immigrant smugglers, not the people who cross the border illegally merely to work.

"We don't go after the addicts on the street," Arpaio said. "We go after the peddlers. Same philosophy."

The Maricopa County Attorney's Office, however, is considering whether to charge these immigrants as co-conspirators. County Attorney Andrew Thomas (search) said he wants the new law to have an ancillary effect on reducing crimes linked to illegal immigration, such as murders, extortion and kidnappings.

"We will be able to have a multiplier effect," Thomas said.

The state is also working to establish a pilot project that would assign a dozen Arizona Department of Public Safety officers to assist local police and federal agents in immigration cases.

Local and state authorities have long pursued cases against immigrants who violate Arizona law, but they previously haven't been able to arrest smugglers, unless they committed state crimes.

Political pressure has been mounting for the state to do more since the federal government tightened enforcement of the borders in Texas and California in the mid-1990s and a heavy flow of illegal immigrants began coming through Arizona.

Last year, Arizona voters approved a law that denied some government benefits to illegal border-crossers. State legislators then passed the law that would allow local and state police to arrest immigrant smugglers, but didn't provide any additional money for police. Some local officials have said it will be of limited use because they don't have the time or money to build cases against smugglers.

Santa Cruz County Attorney George Silva, whose jurisdiction includes 50 miles of the U.S.-Mexico border, said his office only has a $900,000 budget and eight attorneys.

"It's awesome that Andrew (Thomas) can open up a unit, but I can't afford it," said Silva, who will consider enforcing the law on a case-by-case basis if federal authorities can't prosecute smugglers.

Another difficulty local authorities will face is taking into custody immigrants who aren't smugglers but are key witnesses in smuggling cases and have committed no state crimes.

"We can't hold those people because we don't enforce federal law," Arpaio said.

Elizabeth Gilbert, the attorney running Thomas' smuggling unit, said county prosecutors could ask state or federal authorities to make arrangements for the witnesses to remain in Arizona while cases are pending.