Prominent Black Lives Matter activist DeRay Mckesson arrested at Alton Sterling protest in Baton Rouge _lowres

Police arrest activist DeRay McKesson during a protest along Airline Highway, a major road that passes in front of the Baton Rouge Police Department headquarters Saturday, July 9, 2016, in Baton Rouge, La. Protesters angry over the fatal shooting of Alton Sterling by two white Baton Rouge police officers rallied Saturday at the convenience store where he was shot, in front of the city's police department and at the state Capitol for another day of demonstrations. (AP Photo/Max Becherer)

A federal appeals court says a Baton Rouge police officer injured while attempting to arrest protesters after the 2016 killing of Alton Sterling can sue one of the protest’s organizers on the grounds he acted negligently by leading people to block a highway outside police headquarters.

The officer, identified in court records only as John Doe, had sued DeRay Mckesson, of Baltimore, and other protesters who gathered as members of the Black Lives Matter movement. A federal judge had thrown out Doe’s lawsuit, citing First Amendment rights and noting Black Lives Matter was too loosely organized to sue.

In a ruling Wednesday evening, the 5th U.S. Circuit Court of Appeals said Doe should be able to argue that Mckesson didn’t exercise reasonable care in leading protesters onto Airline Highway, setting up a confrontation with police in which Doe was injured by a thrown concrete block.

Mckesson, reached Thursday for comment, said "I’m disappointed and troubled by the 5th Circuit’s reversal of the district court decision. I am currently exploring my legal options and will respond formally soon." Doe's lawyer Donna Grodner called the ruling "a stand-up victory for the Baton Rouge PD."

Circuit Judge E. Grady Jolly, writing for a unanimous three-judge panel, said, “Mckesson should have known that leading the demonstrators onto a busy highway was most nearly certain to provoke a confrontation between police and the mass of demonstrators, yet he ignored the foreseeable danger to officers, bystanders, and demonstrators, and notwithstanding, did so anyway.”

The court said it wasn’t addressing whether Doe’s arguments were valid.

“Our ruling at this point is not to say that a finding of liability will ultimately be appropriate,” Jolly wrote. “We are simply required to decide whether Officer Doe’s claim for relief is sufficiently plausible.”

U.S. District Judge Brian Jackson had ruled that Black Lives Matter was a social movement and that Doe's lawsuit had no suitable target in that regard. The 5th Circuit agreed.

"The district court took judicial notice that (Black Lives Matter) is a 'hashtag' and therefore an 'expression' that lacks the capacity to be sued," the judges said.

A Baton Rouge police officer shot Sterling, who was armed, outside a Baton Rouge convenience store in 2016 after being summoned to the store. Sterling’s death set off days of protests, including the July 9, 2016, protest on Airline Highway outside the Baton Rouge Police Department headquarters. Doe was among the officers at the scene to arrest protesters after they failed to clear the roadway.

According to the 5th Circuit, Doe was struck in the head and suffered the loss of teeth, a jaw injury, a brain injury, a head injury, lost wages, “and other compensable losses.”

Follow Joe Gyan Jr. on Twitter, @JoeGyanJr.