So nicely said : Even if there is no law forbidding photography in the MUNI System, the Fare Inspectors have the right to refuse you service for any reason they choose, including taking photographs. Once they refuse you service they can swear out a citizens arrest for trespassing. I, or other officers, will book you and you’ll spend the rest of your weekend in jail. It won’t be for taking photographs, so your weekend would be ruined yet you’d never get a chance to argue the matter of taking photographs before a judge (Officer Ryan , San Francisco police department, speaking to a a freelance photographer, as described somewhere and on Boing Boing)