The Supreme Court dealt Big Brother a blow on Monday with a landmark ruling for digital privacy rights in Chatrie v. United States. Conservative Justices John Roberts, Brett Kavanaugh, and Neil Gorsuch joined the liberal bloc of Justices Sonia Sotomayor, Elena Kagan, and Ketanji Brown Jackson in finding that smartphone location data is subject to privacy protections under the Fourth Amendment. Though consequential, the case has gone largely overlooked amid this week’s deluge of high-profile rulings, including the decision to block President Donald Trump’s 2025 executive order attempting to overturn the guarantee of birthright citizenship. It marks the Court’s first decision on digital surveillance since 2018, when it found that law enforcement’s warrantless search of cell site location history violated the Fourth Amendment.

To better understand the implications of Chatrie, I hopped on the phone with Stevie Glaberson, director of research and advocacy at Georgetown Law’s Center on Privacy and Technology. The Center filed an amicus brief in the case alongside the Electronic Frontier Foundation and the ACLU. Glaberson helped break down Chatrie and what the Court’s ruling means in an age of growing digital surveillance.

This interview has been edited for length and clarity.

At the center of Chatrie is law enforcement’s use of a “geofence warrant” to identify the potential suspect of a bank robbery in 2019. What are geofence warrants, and how do they differ from regular search warrants?

A geofence warrant is one of the kinds of warrants that people sometimes refer to as “reverse warrants.” When you think about a traditional warrant, the police are supposed to have particularized suspicions—they’re supposed to be going to a neutral decision maker, like a judge or a magistrate, to show their reasons for suspecting that a certain person or a certain place has evidence of a crime that they’re investigating.

In the case of geofence warrants, [the police] don’t have a particular person in mind, and they sort of work backwards from a location. They draw a line around that location and ask the company, in this case Google, for all the devices that can be found within that location at the relevant time.

In this case, the police drew a line around the bank and asked Google for all of the devices that could be found within that space during the time the robbery occurred. That space didn’t just involve the bank. There was a church in the immediate area, and there might have been people’s homes or other businesses.

Have police increased their use of geofence warrants in recent years? How long has this search tactic been used?

“What was happening here is something that........

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