This week the California legislature passed a bill that requires all smartphones to include a “kill switch” that can remotely render the device inoperable. Although created to deter smartphone theft, this kill switch mandate could actually become a nefarious tool co-opted by government to suppress protests.

Kill switch mandates suffer a variety of flaws that CDT has discussed previously. However, the California bill is especially troubling on the issue of police using the feature to shut down phones. The legislation states that government agents may use the kill switch so long as their activities comply with Section 7908 of the Public Utilities Code. This law allows governments to disrupt communications under certain guidelines with judicial authorization, but also includes an “emergency” exception that requires no independent approval.

Police could use the kill switch to shut down all phones in a situation they unilaterally perceive as presenting an imminent risk of danger. This means that police could use the kill switch to shut down all phones in a situation they unilaterally perceive as presenting an imminent risk of danger. It’s not hard to imagine law enforcement putting such a label on a protest: Managers of the BART subway system shut down cell service in four stations just prior to planned anti-police demonstrations in 2011, claiming the disruptive measure was justified by public safety concerns.

This week’s events in Ferguson, Missouri highlight the risks of abuse all too clearly. Police have repeatedly attempted to disrupt protests and ordered both demonstrators and press to turn off recording devices. If the California bill were in place in Missouri, these officers might deploy the government kill switch alongside tear gas and rubber bullets, using the mandated technology to stop coordination between protesters, cut off access to outside information, and shut down video recordings that can deter police misconduct.

The purpose of the California kill switch bill may be to turn stolen phones into worthless “bricks,” but in its current form it could be used to brick protests that police disapprove of. Such a measure is unnecessary, and highly dangerous to the exercise of civil liberties. The bill is now before Governor Jerry Brown, who has a poor record on tech issues that pit police power against civil liberties; last year he vetoed a bill that would have required police to obtain a warrant to read emails over six months old (those not already covered by a warrant requirement).

So long as it contains the threat of disruption of demonstrations, the choice on this measure should be clear: It’s time to kill the kill switch bill.