Is Boston truly looking out for immigrants? Not in this case.

Amy Grunder held a sign as Mayor Walsh spoke at a rally supporting immigrant families to speak out against the Trump Administration's change to the "public charge" provision, which would increase the number of government programs that count against an immigrant when applying for a visa or green card. Jessica Rinaldi/Globe Staff/Globe Staff

Something is seriously amiss if the Trump administration protects the rights of an undocumented worker better than the city of Boston does.

Yet that conclusion is hard to avoid if one believes the allegations in a federal Department of Labor complaint filed last week. In it, Labor Secretary Alexander Acosta accuses a South Boston employer of retaliating against a worker, badly injured on the job and seeking compensation, by trying to have the worker deported — with help from the Boston Police Department.

Until the lawsuit was filed, labor and immigration advocates had no idea of the extent to which Boston police were involved in the case. They are shocked, and deeply troubled — especially given Mayor Marty Walsh’s repeated assurances that immigrants can trust police.

First, the case. The worker, Jose Martin Paz Flores, had a job taping drywall for Tara Construction. He fell off a ladder and broke his femur in March 2017, an injury that required immediate surgery. But Paz — a father of five — could not get compensation for that injury because the company’s workers’ compensation insurance policy had lapsed. Paz is entitled to the benefits regardless of his immigration status.

The Occupational Health and Safety Administration began investigating the accident. Advocates for Paz, and the Department of Labor, say Tara Construction CEO Pedro Pirez set about making his injured worker problem disappear by trying to get Paz deported.

“Paz would not have been arrested . . . if he had not reported his injury to Tara Construction and caused the OSHA inquiry to be initiated,” alleges the complaint, first reported by WBUR.

The suit alleges Pirez called a Boston police detective to tell him he was worried Paz had given a false name (Paz went by only part of his name, Martin Paz at Tara, but in a call with Pirez, the hospital identified him as Jose Flores). That detective, a relative of Pirez’s, gave the information to Sergeant Detective Gregory Gallagher, who is on the joint ICE/Boston Police task force. Gallagher alerted ICE.

The Labor Department complaint calls Pirez’s concern about a false name “pretextual.” Pirez’s attorney Daniel Dwyer says it was genuine, his call to the detective driven by fear that Pirez himself could get into trouble for employing a worker using a false name.

Whatever his motivation, attorneys and the Labor Department claim that, on May 10, 2017, Pirez lured the injured worker to Tara Construction’s South Boston office with an offer to help him meet his expenses. Paz was suspicious , his attorney said, but went to the meeting, where Pirez gave him $500 in cash.

As Paz left the office, a Boston police detective and immigration agents were waiting for him. They arrested him as his 2-year-old son sat screaming in his car. The complaint alleges Pirez coordinated the arrest with Gallagher. Pirez denied it, but Gallagher himself, and phone records and text messages, gave the lie to that claim: According to the complaint, the two were in frequent contact at the time of Paz’s arrest.

Pirez “didn’t intend for all of this to unravel the way it did,” Dwyer said. “He’s a nice guy.”

Paz, who fled Honduras 18 years ago, had been ordered deported in 2002, after he missed an immigration hearing. After his 2017 arrest he spent 12 days in jail, where his injured leg was shackled, and he was without pain medication for days.

For those who have now concluded that Paz and his family deserved everything they got because he was in the country without authorization, a note: Retaliating against employees for asserting their rights under federal labor law is illegal, regardless of the worker’s immigration status. If an employer can violate the rights of undocumented immigrants with impunity, he could violate those of others too. And if he can exploit and abuse immigrant workers without consequence, he is more likely to employ them over those with greater protections.

The complaint alleges Pirez’s actions “would dissuade a reasonable worker from reporting an injury or causing an OSHA proceeding to be instituted.”

Dwyer, Pirez’s attorney, says his client was not retaliating against Paz. He says Pirez, and Tara Construction, were happy to pay the worker for his lost wages and medical expenses in the months following the accident, settling with him gladly, eventually. That comes as news to Paz’s labor attorney, Stacie Sobosik, who says Pirez fought a settlement, “tooth and nail, every step of the way” in court, until an insurance company finally settled with Paz in December 2017. Paz now has authorization to work, and his immigration case has been reopened.

Those claims and counterclaims will be settled by a judge soon enough.

But there’s another part of this case that will be harder to put to rest. Those who serve immigrants and workers say it will have a chilling effect, discouraging workers from reporting abuses, and diminishing trust in the police.

Sobosik, the labor attorney who helped Paz finally receive compensation, said that, before this case, she told clients worried about their immigration status that Massachusetts, and especially Boston, was a safe place for them to assert their rights.

“Now that we’ve seen a more clear link between local law enforcement and ICE detailed by the Department of Labor, I no longer feel comfortable telling people their immigration status doesn’t matter,” Sobosik said.

Boston police spokesman Sergeant John Boyle said police became involved in the Paz case because they had received information that the worker was involved in criminal activity. He could not be more specific about the alleged offense, he said, because the law, and the integrity of the investigation, would not allow it. Paz’s attorneys say they have no idea what criminal matter, apart from the alleged false name, Boyle is referring to.

The mayor stood by the BPD.

“Boston values and respects immigrants,” he said in a statement. “And we will continue standing by our immigrant community who make positive contributions to our city each and every day. A safe city is our first priority, which is why BPD will work with any state or federal authorities if criminal activity is in question for any resident in Boston.”

Taking a stand against the federal immigration crackdowns just over two years ago, Walsh said, “for as long as I am mayor, I will never turn my back on those who are seeking a better life. We will continue to foster trusting relationships between law enforcement and the immigrant community.”

That trust has just taken a massive hit.

Correction: Due to incorrect information provided to the Globe, an earlier version of this story misstated the union status of Paz’s job with Tara Construction.