“Mr. Barr needs a refresher course on the basics in U.S. history,” historian Gerald Horne said.
Many experts are criticizing the move as an inappropriate use of federal resources for Trump’s personal legal matters.
The Justice Department is directed to release its list of “anarchist jurisdictions” within 14 days.
Activists view the application of gang laws as a targeted attempt to suppress police accountability protests.
Ex-officials say the career employee was replaced just weeks before the election with someone seen as more partisan.
The House Judiciary Committee questioned Barr about his actions against BLM protesters and opposition to voting by mail.
Barr had said he wasn’t aware of protests in Michigan, where some had called for violence against Gov. Gretchen Whitmer.
The attorney general is set to defend his controversial actions and accuse Democrats of seeking to discredit him.
Attorney General William Barr ordered the Bureau of Prisons to deploy militarized units to confront protesters in D.C.
The letter writers cite four instances of the attorney general violating his obligations to the American people.