Monday's ruling by the 9th U.S. Circuit Court of Appeals rejected arguments by porn industry leaders that the requirement inhibits the industry's First Amendment free-speech rights.
The ordinance adopted by voters in 2012 was championed by the AIDS Healthcare Foundation and other advocates as a means of reducing sexually transmitted diseases.
The porn industry says its past experience with condoms has taught it that viewers don't want to watch films in which they are used.
The industry also says its own safety efforts, including regular testing of performers for sexually transmitted diseases, eliminate the need for condoms.