According to BuzzFeed News, Democratic Senator Ron Wyden and Representative Ted Lieu will introduce legislation later today that seeks to restrict police use of international mobile subscriber identity (IMSI) catchers. More commonly known as Stingrays, police frequently use IMSI catchers and cell-site simulators to collect information on suspects and intercept calls, SMS messages and other forms of communication. Law enforcement agencies in the US currently do not require a warrant to use the technology. The Cell-Site Simulator Act of 2021 seeks to change that.

IMSI catchers mimic cell towers to trick mobile phones into connecting with them. Once connected, they can collect data a device sends out, including its location and subscriber identity key. Cell-site simulators pose a two-fold problem.

The first is that they’re surveillance blunt instruments. When used in a populated area, IMSI catchers can collect data from bystanders. The second is that they can also pose a safety risk to the public. The reason for this is that while IMSI catchers act like a cell tower, they don’t function as one, and they can’t transfer calls to a public wireless network. They can therefore prevent a phone from connecting to 9-1-1. Despite the dangers they pose, their use is widespread. In 2018, the American Civil Liberties Union found at least 75 agencies in 27 states and the District of Columbia owned IMSI catchers.

In trying to address those concerns, the proposed legislation would make it so that law enforcement agencies would need to make a case before a judge on why they should be allowed to use the technology. They would also need to explain why other surveillance methods wouldn’t be as effective. Moreover, it seeks to ensure those agencies delete any data they collect from those not listed on a warrant.

Although the bill reportedly doesn’t lay out a time limit on IMSI catcher use, it does push agencies to use the devices for the least amount of time possible. It also details exceptions where police could use the technology without a warrant. For instance, it would leave the door open for law enforcement to use the devices in contexts like bomb threats where an IMSI catcher can prevent a remote detonation.

“Our bipartisan bill ends the secrecy and uncertainty around Stingrays and other cell-site simulators and replaces it with clear, transparent rules for when the government can use these invasive surveillance devices,” Senator Ron Wyden told BuzzFeed News.

The bill has support from some Republicans. Senator Steve Daines of Montana and Representative Tom McClintock of California are co-sponsoring the proposed legislation. Organizations like the Electronic Frontier Foundation and the Electronic Privacy Information Center have also endorsed the bill.