This week, EFF has seen censorship stories move closer and closer to home — first Iran, then the UK, and now San Francisco, an early locus of the modern free speech movement. Operators of the Bay Area Rapid Transit system (BART) shut down cell phone service to four stations in downtown San Francisco yesterday in response to a planned protest. Last month, protesters disrupted BART service in response to the fatal shooting of Charles Blair Hill by BART police on July 3rd. Thursday’s protest failed to materialize, possibly because the disruption of cell phone service made organization and coordination difficult.

Early reports indicated that BART cut off cell phone service by approaching carriers directly and asking them to turn service off. Later statements by James Allison, deputy chief communications officer for BART, assert “BART staff or contractors shut down power to the nodes and alerted the cell carriers” after the fact. AT&T, Sprint, Verizon, and T-Mobile have not yet made comment as to whether or not they were complicit in the shutdown.

Obviously, we'd like to know exactly what the carriers said to BART, but many other unanswered questions remain as well. Was pulling the plug on people's phones a quick, on-the-spot decision, or part of a protest-response plan vetted by BART's lawyers? Who decided that blocking all cellphone calls at these BART stations was the right response to news that there might be a protest? Were the carriers ever in the loop about this plan or action? Who decided that the news of this planned protest justified the shutdown? How do we know this isn't going to happen again?

Indeed, BART said today that it had instituted the following rules, including:

No person shall conduct or participate in assemblies or demonstrations or engage in other expressive activities in the paid areas of BART stations, including BART cars and trains and BART station platforms.

What does that mean? We can't talk?

One thing is clear, whether it’s BART or the cell phone carriers that were responsible for the shut-off, cutting off cell phone service in response to a planned protest is a shameful attack on free speech. BART officials are showing themselves to be of a mind with the former president of Egypt, Hosni Mubarak, who ordered the shutdown of cell phone service in Tahrir Square in response to peaceful, democratic protests earlier this year. Free speech advocates have called out British Prime Minister David Cameron for considering new, broad censorship powers over social networks and mobile communication in the UK, and we are appalled to see measures that go beyond anything Cameron has proposed being used here in the United States.

Cell phone service has not always been available in BART stations. The advent of reliable service inside of stations is relatively recent. But once BART made the service available, cutting it off in order to prevent the organization of a protest constitutes a prior restraint on the free speech rights of every person in the station, whether they’re a protester or a commuter. Freedom of expression is a fundamental human right. Censorship is not okay in Tahrir Square or Trafalgar Square, and it’s still not okay in Powell Street Station.