U.S. Attorney Andrew Lelling rejected calls to bar federal immigration agents from operating in state courthouses Wednesday.

Lelling, who was appointed to his position by President Donald Trump in Dec. 2017, said Immigration and Customs Enforcement agents have a right to pursue and detain unauthorized immigrants, especially if they face criminal charges.

"I have no plans to prosecute judges," Lelling said. He would not comment on the case of the Newton District Court judge accused of helping a defendant use a backdoor to evade ICE, but said that federal agents are obligated to enforce the law.

Read more: Massachusetts State Judge Suspected Of Aiding An Immigrant To Flee ICE

"And as a corollary to that, if you obstruct what they're doing, you're committing a federal crime because you are obstructing enforcement of a federal law," Lelling said. "In an environment as politicized as this one, it seems to me people need to be reminded about this sometimes."

In July 2017, Massachusetts' highest court ruled that local law enforcement cannot hold a person in custody for violations related only to immigration.

Lelling discussed several topics at the second annual media round table at his Boston office, detailed below:

Massachusetts State Police Investigation
Lelling said the investigation into the abuse of overtime at the State Police Department is ongoing.

"We don’t relish this kind of enforcement, but it appears necessary to do it,” Lelling said. "It appears necessary, from what we've seen so far, to clean house a little bit at the state police."

Lelling said he cannot give an end point as to when the investigation will end.

"I do think it's in the public interest that we do this with all deliberate speed because the state police ... needs to kind of turn a corner. It needs to get past this," he said.

Warning Doctors About Opioid Prescriptions
In November, Lelling wrote letters to a number of Massachusetts doctors and medical professionals, warning them that their opioid prescription practices were a “source of concern.”

Read more: U.S. Attorney Warning Doctors About Prescribing Opioids

Lelling said that he "would not say these letters are a precursor" to the recent arrest of a Massachusetts doctor by Attorney General Maura Healey's office on manslaughter charges for an opioid prescription.

"The point of the letters was essentially to use the authority of my office to remind prescribers that they need to be very careful with what is, in this day and age, literally a deadly substance,” Lelling said.

Lawrence Opioid Pipeline Crackdown
Lelling called Lawrence a “source city” for fentanyl and heroin.

“Lawrence is one of the top priorities in this office for drug enforcement," he said. "You will see enforcement action after enforcement action in the Lawrence area designed to make that city an uncomfortable place for people who sell drugs there.”

Lelling says drugs are "pouring" into New Hampshire and Maine via Lawrence.

Harvard Admissions Lawsuit
Lelling said his office sent someone to attend the trial in which Harvard University was accused of discriminating against Asian Americans in their admissions practices. They weren't sent at the request of the civil rights division in Washington D.C., he said, but because "it's a case of public importance."

"It wouldn't surprise me if [the case went to the Supreme Court]," Lelling said. "You know, sometimes the Supreme Court takes an affirmative action case, sometimes it does not. It's obviously an extremely sensitive and highly political issue. And so really all bets are off for that kind of thing."

Criminal Justice Reform by Congress
Lelling said his office is closely following a criminal justice reform bill, which would liberate thousands of federal prisoners jailed for non-violent crimes, change mandatory minimums and reduce sentences in certain cases.

“That bill, if passed, would create significant changes in federal prosecution,” he said.

MS-13 Gangs "Eradicated"
Lelling called the reduction of MS-13 "one of the biggest success stories of the last year."

“We have all but eradicated MS-13 in the Greater Boston area. We’re running out of MS-13 targets,” Lellling said. He said the vast majority of the targets his office charged either pleaded guilty or were convicted at trial.