SCOTUS Just Issued Its Biggest Privacy Ruling in Nearly a Decade

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 the founders could not have imagined when they were debating the Fourth Amendment.”

This technique did not exist previously. It’s only possible because of the way technology works now, and a big part of what the Court said in its opinion is that what was happening here is something that the founders could not have imagined when they were debating the Fourth Amendment, a kind of surveillance and a kind of police investigation that would not have been possible. It was not previously possible for the police to retroactively tail all of us into private businesses and homes, throughout our days, at this level of granularity.

The interesting thing about the Chatrie case is that the particular three-step process that happened here, Google had already said that they are no longer doing it the same way. But that does not mean that there are not other ways for the police to access this type of information.

Can you explain that three-step process ?

The more common thing is for police to just ask a company or a person for a specific thing in a specific location. Here, the warrant described this three-step process that, once the judge approved it, Google and the police would just go through [the data] on their own without returning to the magistrate.

First, Google would look in that physical location, the box the police had drawn, and return anonymized information about all the devices. The police would then look at what Google gave them and try to narrow down which of the devices they wanted more information about. In this case, the initial step returned 19 devices. And the police said, Okay, we want information about these nine.

And what’s important to note is that in this case they were only looking for one suspect. So, at each of these steps, they’re getting the data of people that are affirmatively not the suspect. And it’s important to recognize that these kinds of searches could draw in all of us, regardless of any suspicion or not.

So the police asked Google for more information about those nine accounts to look at where else those devices went before and after the crime. The identities of the people were still not being revealed to the police, but they could now see two hours of really granular location information about all the places those devices came from and went to during that period. Google captures location data once every two minutes, and it’s pretty precise about where a person is. It also can capture elevation data, if this person went to the doctor’s office on the third floor, rather than the insurance salesman on the tenth floor.

“We found…that the majority of American adults, as of 2021, were in Department of Homeland Security immigration databases and could be located by ICE and CBP.”

From that return of nine sets of more granular information over two hours, the police then were supposed to look through that and identify the devices they wanted unmasked, to learn the identities of the people who owned those devices. And in this case, they didn’t just ask for the person they eventually prosecuted, Mr. Chatrie. They asked Google to de-anonymize three accounts, so, once again, people who affirmatively were not then the suspect.

What did the Supreme Court have to say about this process?

Six justices got in line behind the idea that the decision [from a lower court] should be vacated, that a search did happen here according to the Fourth Amendment and needs to be more closely reviewed. Five justices signed on to the main opinion written by Justice [Elena] Kagan. And Justice Gorsuch wrote his own opinion that gets to the same place, but through a different avenue.

Justice Kagan’s opinion goes through the most recent, really seminal opinion on Fourth Amendment privacy in the digital era, which is Carpenter. That’s a case about cell site location information, which is pretty similar to the Google location history that was at issue here. And the majority opinion decides that, in accordance with Carpenter in 2018, a search did occur here when the government went to Google and asked for all of this information, and so we need to look very closely at whether the warrant that the police got was appropriate. The opinion leaves for another day the questions that will ultimately resolve the case about whether the warrant itself was appropriate, but it decides that, for purposes of the Fourth Amendment, the government did conduct a search here.

One thing that’s really important about this decision is that it says a third-party doctrine does not apply in this case. The third-party doctrine is an exception to the Fourth Amendment that risks really swallowing the rule for all of us in today’s digital economy. It’s the idea that once you voluntarily share information with someone else, a third party [like Google], you lose all reasonable expectations of privacy in that information and the Fourth Amendment doesn’t apply. And in this case, Justice Kagan’s opinion really importantly says the third-party doctrine does not apply here, just by using a cell phone the way cell phone users do, we don’t give up our rights to our private information.

What are the broader implications of the Court’s ruling? Do you expect this case to have a ripple effect?

So if you read Justice [Samuel] Alito’s dissent, he basically says this is coming for all digital surveillance, which in our book is probably a good thing, but he says it as though it is a terrible thing.

I think this is probably the most significant Supreme Court ruling on the Fourth Amendment since Carpenter. What practical impact it will have remains to be seen, but I think it is an incredibly important development that the Supreme Court is not just extending the third-party doctrine to to all cases and saying that the introduction of a layer of corporate interaction in our lives removes all expectations of privacy.

Because basically, in the last few decades, every single thing we do, from communicating with our families to managing our finances to even thinking our own private thoughts, corporations have sort of wormed their way into all of those processes and are mediating all of our human interactions, sometimes the most sensitive facets of our lives.

“Everybody should recognize that placing these limits on police and on government is vital…for community and for democracy.”

And if the mere fact that a corporate tool was in the middle of all of that meant that we had no expectation of privacy whatsoever, that would be the exception that swallows the Fourth Amendment. I don’t know whether this opinion will meaningfully change our day-to-day, but it is a step in the right direction to say that the Fourth Amendment really does still mean something. Privacy is still a value, and one that we’re going to protect.

It seems like people are increasingly aware of and concerned about surveillance, but thinking about things like First Amendment concerns, why does this decision matter for everyday people who haven’t committed or aren’t suspected of having committed any crimes?

All of these techniques, from geofence reverse location searches to police use of facial recognition technology, impact all of us. The companies and the police and the federal government don’t necessarily distinguish when they vacuum up information, when they buy information from data brokers, or when they use facial recognition on a crowd, they don’t distinguish between folks that they have a particular interest in and folks that they don’t. They are just vacuuming up information on everybody.

We found in our research that the majority of American adults, as of 2021, were in Department of Homeland Security immigration databases and could be located by ICE and CBP. So, at a practical level, it impacts all of us, and it has really serious implications on our ability to live our lives and do the things that we want to do together. Because very quickly information about one of us becomes information about a whole group of us, and the police can use these kinds of techniques to surveil and track us from afar, without our knowledge, and identify when we go to protests or come together in community.

So everybody should recognize that placing these limits on police and on government is vital to maintain any kind of any hope for communal action for community and for democracy.