But far-right and far-left groups, as well as looters and rioters, have seized on the protests to commit acts of violence, including deadly shootings — serious crimes that some federal prosecutors said could not be dismissed out of hand as anomalous, particularly as the threat from extremist groups grows.
Two men associated with the Boogaloo, a far-right movement that supports the coming of a second civil war, were arrested on terrorism-related charges last week. Prosecutors said they used the protests as cover to try to sell weapons to the Palestinian militant group Hamas, which the United States and other countries consider a terrorist group, and to use the money to support the Boogaloo movement.
Mr. Barr told federal prosecutors on the call that they needed to crack down on looting, assaults on law enforcement officers and other violence committed during the protests that have continued across the country since George Floyd, a Black man in Minneapolis, was killed by the police in May.
Mr. Barr mentioned sedition as part of a list of possible federal statutes that prosecutors could use to bring charges, including assaulting a federal officer, rioting, use of explosives and racketeering, according to the people familiar with the call. Justice Department officials included sedition on a list of such charges in a follow-up email.
After Mr. Barr spoke, Richard P. Donoghue, a top aide to the deputy attorney general, interjected to note that some of the U.S. attorneys on the call worked in districts where violence during protests was less common, and that the federal prosecutors may not need to use tools as aggressive as sedition charges.
Mentioning that he had visited Portland, Ore., Mr. Donoghue also assured the prosecutors that the Justice Department would support all efforts to crack down on violence.
“If Barr was saying that if you have a sedition case, then bring it, that is fine,” Mr. Rosenberg said. “But if he is urging people to stretch to bring one, that is deeply dangerous.”