(Reuters) - A Louisiana police officer cannot sue Black Lives Matter because it is a social movement, a U.S. judge ruled on Thursday, finding the campaign could not be held responsible for injuries he got at a protest.

FILE PHOTO: A supporter of the UK branch of "Black Lives Matter" hands out placards at the start of a demonstration in London, Britain August 5, 2016. REUTERS/Peter Nicholls/File Photo

The unidentified officer sued Black Lives Matter and an activist involved in a July 2016 protest in Baton Rouge, Louisiana, where the officer was struck by a rock.

The Black Lives Matter movement began with the hashtag #BlackLivesMatter on social media in 2012 after black high school student Trayvon Martin was shot dead in Sanford, Florida, by neighbourhood watch volunteer George Zimmerman. Zimmerman was acquitted of second degree murder and manslaughter.

It grew into a nationwide movement in response to the use of excessive force by police, particularly against black men.

“‘Black Lives Matter,’ as a social movement, cannot be sued, however, in a similar way that a person cannot plausibly sue other social movements such as the Civil Rights movement, the LGBT rights movement or the Tea Party movement,” Chief Judge Brian Jackson of a U.S District Court in Baton Rouge wrote in a 24-page ruling.

While the movement itself lacked the capacity to be sued, an associated entity could be held liable, Jackson said. But the judge found the officer had not made a sufficient case against such a group or an individual involved and dismissed the lawsuit.

Billy Gibbens, an attorney for DeRay Mckesson, the activist named in the lawsuit, said his client “does not condone violence of any kind, and we are very sorry that the officer was injured.”

“The court was absolutely correct to find that DeRay is not responsible for the criminal conduct of an unidentified person,” Gibbens said in an email.

Attorneys for the officer, Black Lives Matter and the activist named in the lawsuit did not immediately respond to requests for comment.

It was not clear how the ruling might affect a related lawsuit filed by an officer who was wounded during protests last year in Baton Rouge.