The Justice Department is investigating Minnesota officials, including Gov. Tim Walz and Minneapolis Mayor Jacob Frey, under the theory that they conspired to impede federal immigration agents, a senior law enforcement official and person familiar with the matter told NBC News.

The law at issue is a rarely used federal statute with roots in the Civil War era. It was one of the statutes listed in a memo from Attorney General Pam Bondi last month, obtained by NBC News, that spelled out the statutes that she wanted federal prosecutors to use to target individuals she dubbed domestic terrorists.

CBS News first reported on the investigation.

In a statement Friday regarding reports of the investigation, Walz said, “Two days ago it was Elissa Slotkin. Last week it was Jerome Powell. Before that, Mark Kelly. Weaponizing the justice system and threatening political opponents is a dangerous, authoritarian tactic.”

“The only person not being investigated for the shooting of Renee Good is the federal agent who shot her,” he said.

Frey said in a statement in response to reports of the DOJ investigation that he “will not be intimidated.”

“This is an obvious attempt to intimidate me for standing up for Minneapolis, our local law enforcement, and our residents against the chaos and danger this Administration has brought to our streets.” he said.

He added that, “Neither our city nor our country will succumb to this fear. We stand rock solid.”