WHEN THE TRUMP ADMINISTRATION busts someone for improperly alerting the feds about an undocumented immigrant, you can bet the case is pretty strong.

The US Department of Labor sued Tara Construction and its CEO over what the department claims was a retaliatory tip-off to the authorities about one of Tara’s workers who is in the country illegally. The CEO allegedly communicated with Boston Police Department officers and facilitated the arrest of someone who had worked for Tara, according to the suit.

Now the American Civil Liberties Union of Massachusetts wants to learn more about something the Labor Department turned up in its investigation — the existence of a joint task force between the Boston police and Immigration and Customs Enforcement.

Shannon Dooling, a WBUR reporter, has covered the case since the beginning two years ago when Jose Martin Paz Flores was arrested by immigration enforcement, leaving his family anxious and without income. He was freed from jail after a couple weeks. Originally from Honduras, Paz came to the US by illegally crossing the southern border.

The arrest occurred a few months after Boston Mayor Marty Walsh claimed that, as a last resort, undocumented immigrants threatened by the Trump administration could use City Hall as a place of refuge.

The Boston City Council in 2014 passed the Trust Act, which bars Boston police from detaining people solely at the request of ICE. The Supreme Judicial Court later ruled that such detentions are unconstitutional. Councilor Josh Zakim told The Boston Globe a few years ago that he would consider another ordinance to further limit local police cooperation with immigration enforcement.

As it turned out, Boston police and the head of a local construction firm appear to have worked in coordination to lock up one undocumented immigrant – Paz. Tara Construction, headed by CEO Pedro Pirez, is located in South Boston and it has done work on a South Bay apartment building, according to its website.

On March 29, 2017, Paz was at a jobsite – the labor complaint doesn’t specify where – when he fell from a ladder and broke his leg. Tara hadn’t paid its premium for worker’s compensation insurance so the company’s insurer denied coverage related to Paz’s injury, according to the lawsuit.

Pirez later contacted Boston Police Detective Juan Seone and asked him to look into Paz’s identity, and Seone got in touch with his colleague, Sgt. Detective Gregory Gallagher, who is the department’s liaison to ICE. Gallagher and Pirez met, and Pirez allegedly communicated to Gallagher when Paz would be stopping by the office to pick up some money, according to the suit. Paz was arrested on May 10, 2017, in front of his young son after leaving Tara’s offices.

The claims in the suit comport with what Tara construction’s attorney, Stephen Murray, told WBUR soon after the arrest: that his client had no communication with ICE. The communication was allegedly with the Boston Police’s liaison to ICE. However, the coordination described by the Labor Department contradicts what Pirez told the Occupational Health and Safety Administration. According to the lawsuit, Pirez “testified to OSHA that he did not communicate with any law enforcement officials about when his meeting with Paz would take place and he had no idea how law enforcement knew where Paz would be when Paz was arrested.”

The labor suit doesn’t get into why immigration enforcement wanted to lock up Paz, but a police spokesperson recently told WBUR that Pirez provided information that Paz was involved in some suspected criminal activity. Paz’s lawyers said they have no idea what that would be.

President Donald Trump has throughout his presidency excoriated cities that provide “sanctuary” to undocumented immigrants and sought more resources for immigration law enforcement. In this case it is Trump’s Labor Department going after a construction firm executive for allegedly helping law enforcement to arrest someone in the country illegally.

At The Boston Globe, columnist Yvonne Abraham concludes that the whole episode has eroded trust between law enforcement and the immigrant community, and writes that if an employer can violate the rights of undocumented immigrants with impunity, he will be more likely to employ undocumented immigrants over others with greater protections.