A district attorney in Massachusetts is considering criminal charges against a U.S. Immigration and Customs Enforcement (ICE) agent who was held in contempt of court for arresting an illegal immigrant in the middle of his trial last month, Fox reports.

The Justice Department stepped in on Wednesday, filing a motion to vacate the contempt order against ICE agent Brian Sullivan. Sullivan had detained Wilson Martell-Lebron, a Dominican citizen, during his trial.

“Our motion is clear: the state court lacked authority to issue the unlawful and erroneous order,” U.S. Attorney Leah B. Foley said. “The Supremacy Clause of the United States Constitution immunizes federal officers from state prosecution—including contempt proceedings—for actions taken in the course of their official duties.”

Suffolk County District Attorney Kevin Hayden’s announcement could put more strain on his relationship with the Trump administration, which has criticized Massachusetts officials for interfering with federal immigration enforcement.

“ICE routinely claims that their actions are improving public safety in Boston, and I’m here today to tell you and to say that they’re doing the exact opposite,” Hayden said. “Let me be clear: ICE’s removal of this defendant represented an unacceptable and unprofessional interference with the defendant’s right to trial.”

The controversy started when Sullivan arrested Martell-Lebron, also known as Juan Carlos Baez, outside a Boston courtroom on March 27. His trial had just begun, and witnesses were starting to testify.

“This action by ICE was troubling and extraordinarily reckless,” Hayden added. “ICE’s actions deprived Mr. Martell-Lebron of his right to a fair trial. It also deprived our office of our intent to hold the defendant accountable for his alleged crime.”

On Tuesday, Foley sent a letter to Hayden warning him to “cease from entertaining or pursuing any charges against Officer Sullivan or any other federal official relating to the arrest of Baez.”

“As you know, Baez was in this country illegally, had prior arrests for serious drug trafficking offenses, and was arrested pursuant to a valid federal warrant,” Foley wrote.

Judge James Summerville weighed in on the case, calling it “a disturbing case. It’s a case of obstruction of justice. It’s a case of violating the defendant’s right to be present at trial and confront witnesses against him. Couldn’t be more serious.”

Martell-Lebron had been on trial for allegedly providing false information on a driver’s license application. His trial was halted after the second day when ICE took him into custody.

Summerville ordered an investigation into Sullivan’s actions and later dismissed the case against Martell-Lebron after ICE refused to release him back to local authorities. Hayden noted that Martell-Lebron had a prior 2009 conviction for trafficking cocaine.