A federal judge has ordered sheriff Joe Arpaio to halt workplace raids which net undocumented people in Arizona, in the latest legal restraint on “America’s toughest sheriff”.

Judge David Campbell ruled on Monday that the raids in Maricopa county were probably unconstitutional and should be stopped pending a federal lawsuit which aims to ban them.

Sweeps by Arpaio’s criminal employment squad detained hundreds of people and fuelled his fame – or infamy, according to critics – as America’s self-styled toughest law enforcer.

Judge Campbell issued a preliminary injunction prohibiting Arpaio and Maricopa county attorney Bill Montgomery from enforcing portions of two Arizona statutes which were used to criminalise undocumented workers. He was responding to a petition by the Phoenix-based immigration-rights group Puente.

“This is a huge deal. It was one of the last remaining things that sheriff Arpaio was doing to terrorise our community and now we’ve taken that away from him,” Carlos Garcia, Puente’s executive director, told the Guardian.

It was the latest legal ruling to curb the sheriff’s ability to crack down on undocumented migrants. His office has been stripped of special federal immigration powers, found guilty of racially profiling Latinos in traffic stops and been investigated by federal authorities for alleged civil rights violations. Last month a federal judge threw out Arpaio’s attempt to sue Barack Obama on the grounds that the president’s immigration reforms were unconstitutional.

Arpaio’s office said: “The citizens of Maricopa county have been stripped of another protection that this state attempted to enact to protect the integrity and identity of its citizens.



“I do not understand how federal law can pre-empt state law when the federal government has proven it has no desire to protect its citizens in these areas. I hope that the decision to appeal this particular opinion is made bravely and quickly.”

Puente and several other defendants filed the class-action against workplace raids last June, saying the raids misused two state identity-theft statutes upon which they were based.

Judge Campbell said the plaintiffs had shown these laws were “likely to be found unconstitutional” and that Puente’s members would face irreparable harm in the absence of a court order enjoining enforcement. The National Day Laborer Organizing Network and the American Civil Liberties Union supported the petition.

Activists hailed the ruling. “When I was led away from my job in handcuffs, I never thought I would see the day that we took Arpaio and Montgomery to court instead of the other way around,” Noemi Romero, who was arrested in a raid in 2012, said in a statement issued by Puente. “We lost our fear and made this lawsuit happen, and now others in our community won’t have to suffer like we did.”