The proceeding stems from an incident last summer, when a San Francisco transit agency shut off the transmitters that allow for cellphone reception in four underground subway stations to disrupt a planned protest over a police shooting.
That protest never materialized, but the cellphone disruption led to weeks of protests and several cyberattacks on the transit agency's websites. Civil-liberties groups condemned the blackout as an intrusion on free speech, and compared it to crackdowns in Egypt and other authoritarian regimes.
The FCC said it would review the issue and develop guidelines for local police agencies.
In Tuesday's filing, the consumer groups argued that blacking out cellphone service would, in almost all circumstances, violate the First Amendment and federal communications law. They also warned that a blackout would threaten, not protect, public safety.
The FCC had asked whether it would be possible to allow only 911 calls during a blackout, but the groups said some people may need to communicate through channels other than 911.
"For example, individuals often provide information to non-emergency channels such as news outlets or publicly-accessible sites like blogs, Twitter, Facebook, or other social media services," the groups wrote, arguing that such communications have important public safety purposes.
The groups also urged the FCC to clarify that even private network providers are not allowed to shutdown wireless service.
"Private entities uncertain about their legal obligations might, out of an abundance of caution or a desire to cooperate with a local authority, be persuaded to interrupt service in instances that hinder public safety efforts or suppress freedom of speech," the groups wrote.