Federal regulators want feedback on whether they should allow government agencies to deliberately jam wireless phone services "for the purpose of ensuring public safety."
Late Thursday, the Federal Communications Commission said it will seek comment on whether to allow government agencies to block cellphone services.
The issue arose last summer when the Bay Area Rapid Transit system in the San Francisco area deliberately shut down wireless service at some stations during protest demonstrations designed to affect train service during rush hour.
"The service interruption last summer drew sharp criticism, and state and local governments have recently grappled with how to address possible future events," the FCC said in the seven-page notice. "Any intentional interruption of wireless service, no matter how brief or localized, raises significant concerns and implicates substantial legal and policy questions."
Other law enforcement agencies have suggested that jamming devices would be useful in controlling "flash mobs" -- groups who coordinate their actions over phones, email or social-media networks.
While many flash mobs are benign, there were some instances last year of criminals using them to coordinate attacks or robberies.
FCC rules bar the use of jamming devices to disable cellphone signals, partly over concerns it would prevent consumers from calling 911 in the case of an emergency.
The agency estimates that about 70 percent of all 911 calls now come from wireless phones. Several prisons and other law enforcement agencies have suggested they need the ability to jam wireless signals.
FCC Chairman Julius Genachowski announced in December that the FCC's staff would look more broadly at the issue of whether it should lift its prohibition on cellphone-signal blocking by government agencies.
On Thursday, the agency asked interested parties to respond to three pages of detailed questions about the pros and cons of changing its regulations.
A request for comment is often the first step toward changes in FCC rules, but it is not clear if the agency's inquiry will eventually lead to any revisions.