The decision by Bay Area Rapid Transit officials to cut off cellphone service Thursday evening – to forestall a planned protest – raises a fundamental question: Do Americans have a basic right to digital free speech or to digitally organized assembly? Because July protests against BART police shootings had turned violent, BART officials took the unusual step to protect public safety, they said. The tactic may have worked: No protests took place Thursday night at BART stations. Temporarily shutting down cell service and beefing up police patrols were "great tool[s] to utilize for this specific purpose," BART police Lt. Andy...