The 2nd District Court of Appeal said Monday that the finding prevents Baron Cohen from being sued by the woman who tried to force him and his crew from an event being filmed.
Richelle Olson sued Baron Cohen in June 2009, claiming she fell and hit her head moments after struggling with the comedian and his crew as she ordered him to leave a charity bingo game.
Her injuries were serious enough to require Olson to use a cane to walk, according to the lawsuit.
Olson initially allowed filming at the game in Lancaster, Calif., but ordered Baron Cohen to leave after he started equating the numbers with the homosexual relationships of his character in the film about a gay Austrian fashionista.
The court ruling states that the comedian's behavior was protected because the comedian was trying to offer commentary on gay stereotypes, culture and homophobia. His conduct was closely tied to those issues, the ruling states.
Olson's attorney Marjorie Marenus did not immediately return a phone message seeking comment.
The unscripted scene did not appear in the final version of "Bruno," which was released in July 2009.
It was the latest legal victory for Baron Cohen, who has been unsuccessfully sued over his movies' inclusion of participants who aren't familiar with the comedian's outlandish characters.
Another Baron Cohen film, "Borat: Cultural Learnings of America for Make Benefit Glorious Nation of Kazakhstan," became a hit in 2006.