> But I suspect it's only a matter of time before the FBI/CIA/NSA (or local PD) will be able to unilaterally decide it's in the "public interest" to suddenly shut off every phone in a particular geofence.
This would be an ineffective way to accomplish that. They'd first have to make a list of all the phones in the target area, and then they'd have to send the lock commands to them, one by one.
Furthermore, even if they went through all that trouble, it only would work on smartphones. The bill does not apply to feature phones, other non-smartphone phones, laptops, or tablets. The bill defines a "smartphone" as a cellular radio telephone or other mobile voice communications handset that includes ALL of the following features:
• Utilizes a mobile operating system.
• Possess the capability to utilize mobile software applications, access and browse the Internet, utilize text messaging, utilize digital voice service, and send and receive email.
• Has wireless network connectivity.
• Is capable of operating on a long-term evolution network or successor wireless data network communications standards.
The bill explicitly says that "smartphone" does not "include a radio cellular telephone commonly referred to as a 'feature' or 'messaging' telephone, a laptop, a tablet device, or a device that only has electronic reading capability".
(Added in edit) Also, while the bill requires that smartphones be equipped with this and that it be on by default, the bill does NOT require that it stay on. Apple's iOS 7 kill switch lets the user turn it off, and I believe that is what Samsung plans to do. People going to protests or other events where they think authorities may try to disrupt communications can simply turn off the kill switch before arriving at the protest.
It would be much more effective to silence a particular area by doing something at the cell tower layer or higher.
> I have a hard time believing that stolen phones are a big enough social problem to warrant a mandate of this scope
Stolen phones account for half of all robberies in San Francisco. In New York, they are 20% and rapidly rising. It's the #1 property crime nationwide, accounting for 1/3 of all property crime. In half of the San Francisco incidents the victims are punched, kicked, or physically intimidated, and in a quarter of them they are threatened with a gun or knife.
That sure seems like a big enough problem to me to try to do something about. We also know that kill switches are effective. In the first five months after Apple put in a kill switch, iPhone thefts dropped 38% in San Francisco, 24% in London, and 19% in New York. We know this wasn't just due to a general lowing of crime rates, because in the same time period overall New York theft went down 10%, and Samsung phone theft went up 40%.