A 250-member sheriff's posse launched patrols in desert areas and major roadways southwest of Phoenix, searching for illegal immigrants to arrest under a new state smuggling law.
The group that began patrols on Wednesday night was made up of Maricopa County sheriff's deputies and members of the department's 3,000-member posse reserve of trained volunteers.
The posse will patrol the area for illegal immigrants who pay smugglers to cross through Arizona, the busiest illegal entry point along the 3,200km US-Mexico border.
"You've got the people of this country and the people of Maricopa County behind you," Sheriff Joe Arpaio told the posse. "You also have the sheriff behind you."
Those who are captured by the posse may end up in jail, charged under the state law that allowed local law enforcement agencies to charge suspected smugglers in Arizona -- it was already a federal crime.
It has been used against more than 100 illegal immigrants in Maricopa County this year.
The law was meant to crack down on smugglers, but under a disputed interpretation, County Attorney Andrew Thomas argues the law also can be applied to the smuggled immigrants themselves.
Thomas maintains illegal immigrants who pay smugglers to enter the US are committing conspiracy to smuggle and can therefore be prosecuted under the state law. It's punishable by up to two years in jail.
"It's going to be a help to the county," posse member D.J. Pigott said. "Illegal immigrants are getting everything that, in my estimation, they should not get. We're being overrun by these people. If the federal government is not going to do it, the sheriff is going to do it."