The Supreme Court’s 6-3 decision in Chatrie v. United States marks one of the Court’s most important Fourth Amendment rulings in the 21st century. While the Court sent Chatrie back to the Fourth Circuit Court of Appeals to decide whether this particular geofence warrant was “reasonable” (and thus Fourth Amendment-compliant), it ruled that this form of surveillance is a search that requires a warrant. Specifically, the Court held that individuals retain a reasonable expectation of privacy in their location history even when held by a third party (in this case Google) and when the surveillance only covered a short duration of time.

The Court’s holding will have crucial ramifications for privacy in the digital age, lifting up a shield against new surveillance technologies and techniques far beyond the geofence warrant that was at issue in this case. But on other emerging surveillance issues related to this case, the future for Fourth Amendment rights remains uncertain. Below, we outline some of the key impacts and open questions from Chatrie, and how the decision will influence the broader landscape for digital privacy rights.

Does Chatrie mark the long-awaited death of the third-party Doctrine?

Throughout the digital age the third-party doctrine—which since its recognition in the 1970s has generally held that records and data held by third parties do not retain Fourth Amendment protections—has been an enormous thorn in the side of digital privacy rights. If applied to modern digital tools, this doctrine would prevent the Fourth Amendment from guarding individuals’ emails and text messages from warrantless searches merely because they’re stored on a server by a digital service provider. This situation was not compatible with democratic society, but protections built into statute by Congress and lower court rulings allowed the Supreme Court to dance around this question for years.

But as the amount of digital services we rely on for our daily lives has become practically endless, the need for clear, strong protections has grown urgent. In today’s world most people casually rely on third parties not just to store in the cloud but to digitally streamline a huge array of highly sensitive information: not just our emails and direct messages, but also our location and movement records, calendars, photos, daybooks and journals, health and medical logs, web browsing activities, and much more.

With Chatrie, the Court tosses the third-party doctrine to the dustbin for these types of digital services. Building on logic it laid the foundation for in the 2018 Carpenter decision (where the Court ruled any cellphone tracking of at least a week required a warrant), Chatrie holds that the third-party doctrine does not apply contingent on a two-pronged test: 1) whether the data shared are highly sensitive, and 2) whether third party’s own control and use of the data was the purpose behind sharing it.

For the first prong, it’s inevitable much ink will be spilled in the future debating whether different types of data clear the hurdle. But it will be a debate over privacy rights held on the most logical terms: How sensitive and revealing is a certain type of data? And how dangerous would it be for the government to access those data without a warrant?

On the second prong, the Court effectively draws out what makes modern digital services so different from the type of entity the third-party doctrine was built for. What matters most for privacy rights is distinguishing whether third-party access was the desired goal. Was data, as the Court puts it, shared “in the normal sense of wanting a third party to see or use it”? (emphasis added). Or, as is often the case for digital services, was “the exposure of that information to [a company] … merely what happens when a user avails himself of one of the services on his cell phone,” whereby “a cell-phone user is not to be viewed as sharing private information with third parties—which then can be freely passed on to the government—just by doing the ordinary things cell-phone users do.”

Are individuals handing over records or data to a third party to be an active and intended sharee, or merely as a steward of those items? Going forward that—rather than a blanket, antiquated rule for all data held by third parties—is the essential distinction.

How will Chatrie shape location tracking in general?

Another major impact of Chatrie will be its holding on how the Fourth Amendment protects electronic location information. When it issued its Carpenter ruling in 2018, the Court said that cellphone tracking for a week or longer required a warrant, but explicitly left open the question of what protections applied for shorter periods of time.

The question has been resolved, with Chatrie firmly establishing Fourth Amendment protections for cell phone location tracking of any length. By recognizing that “the durational bounds on the data actually acquired do little to address the Fourth Amendment’s concern about a too permeating police surveillance,” the Court provides clarity for, and more importantly a strong shield against, cell phone tracking that is short in length yet may still be highly invasive in what it reveals.

This is a major boon to privacy rights, although one that is not without caveats and ongoing questions. First, the Court’s ruling rested in part on the logic that geofence warrants allow the government to place in its crosshairs those locations and events that are especially sensitive, a technique that “enables police officers to focus on precisely those sites” like a house of worship, lawyer’s office, medical clinic, protest, or political rally. Does a warrant protection still exist if this target-the-location tactic isn’t being employed, such as checking the cellphone movements for a suspect over an hour of time when a crime occurred? The answer is likely yes, given the Court’s declaration that “where the Fourth Amendment applies, it applies—regardless of ‘the quality or quantity of information’ the government obtains.” But this may be a point of ongoing litigation in the future.

A broader question is how this ruling will apply to other forms of electronic location surveillance than cellphone tracking. If a warrant is required to track someone’s movement via their phone, does that also apply to mapping someone’s movements with automated license plate readers? What about using drones, especially those paired with automated tag-and-follow tech? Or what if rather than by using a geofence, police want to identify everyone at a protest using facial recognition?

The Chatrie ruling did contain one qualifier that could cut against extending the law in some of these situations. In distinguishing this case from a 1983 ruling (Knotts) that tracking cars via a beeper did not require a warrant, the Court emphasized that the fact that “the surveillance there was confined to public roads …. was crucial to the Court’s decision” whereas geofences and cellphone tracking can roam into private residences. Will this be a key distinction, whereby electronic location tracking into private areas requires a warrant but those methods that are limited to public spaces do not?

It’s hard to imagine this will be the case. After all, it would be both illogical and anathema to privacy rights if the Fourth Amendment required a warrant to track everyone while they were inside a church, an abortion clinic, or a gun shop (or host of other sensitive locations), but allowed the government to freely track everyone as they publicly entered and exited those places.

Exactly what types of location tracking technologies will require a warrant in line with Chatrie will be an important topic for years to come. But for now we have resolution on a matter of great importance: any cellphone location tracking requires a warrant. That is a major boon to privacy, civil rights, and civil liberties.

What does Chatrie mean for geofence warrants in particular? The ramifications of Chatrie on geofence warrants are, potentially, equally significant and limited. The geofence warrant in this case demanded location data maintained by Google through its Location History feature. That data is now stored locally, meaning Google won’t have responsive information to any geofence warrants issued now. But for other businesses that still hold precise location data, Chatrie should provide a degree of clarity. If law enforcement attempts to issue a geofence in the future (or employs new investigative techniques that similarly requests location data for a group rather than an identified suspect) companies now have a clearer roadmap to demand a warrant and push back on demands that are overbroad, burdensome, or otherwise inappropriate. However, as Google was the main known recipient of geofence warrants, it’s unclear how broad the practical impact of this will be.

The strength of guardrails around future geofence warrants is another open question. The Chatrie ruling expressly left for lower courts how to evaluate the proper bounds that would make acting on a geofence warrant a “reasonable” search. One privacy‑protective view would require probable cause that everyone within the geofence committed the crime, a standard that would effectively bar most geofence warrants which often capture innocent bystanders, witnesses, and even unrelated individuals in entirely different buildings or locations who merely happen to be within the fence.

A more permissive approach would be a model suggested by Justice Kavanaugh in oral arguments: to require probable cause that everyone within the geofence would provide evidence as either a suspected perpetrator or a witness to a crime. That standard has legal precedent (in 1978 the Court ruled that a search could occur even if not focused on a suspect so long as there is probable cause it would return evidence) and would provide more flexibility for investigators. But it also risks some abuse in terms of fishing and “surveillance by association” if used in response to crimes that occurred at sensitive events, such as a protest.

Another approach would be to treat each inquiry on a case‑by‑case basis depending on the specific circumstances, the geographic scope of the geofence, its duration, and the degree of judicial oversight at each step. That approach offers greater flexibility to account for specific needs and civil liberties risks, but also increased risk that needed protection won’t be consistently applied. The Court did not choose among these possibilities, and as such the contours of a constitutionally adequate geofence warrant remain unsettled.

What are the ramifications of Chatrie on other reverse warrants?

By declining to set parameters for geofence warrants—and, in particular, establish what principles and limits should apply to a search focused on a group rather than an individual suspect—the Court left open a broader emerging question about “reverse searches” generally. The reverse search category includes reverse keyword searches, reverse IP address searches, reverse AI prompt searches, and other techniques that identify users based on shared conduct (e.g., the websites they visit, the search terms they use, or the addresses they look up) rather than individualized suspicion.

As a baseline matter, Chatrie makes clear that these types of sensitive user data can receive Fourth Amendment protection even when held by a company. The Court did not decide how probable cause and particularity apply to reverse searches, nor did it offer a roadmap for safeguarding innocent individuals incidentally caught up in this form of surveillance. It did not articulate limits on how much discretion officers may exercise when narrowing anonymized data, or minimization structures more generally. As reverse warrants expand and law enforcement officials begin to use new techniques with increasing frequency, lower courts, and specifically magistrate judges who might be unfamiliar with these processes, will have to determine how Chatrie’s holding applies to increasingly complex forms of digital behavior—and how to reconcile those techniques with the Fourth Amendment’s traditional requirement of individualized suspicion.

What does Chatrie mean for the data broker loophole?

Another major question Chatrie draws forth is how to deal with the data broker loophole. In recent years it has become a serious problem that law enforcement and intelligence agencies avoid the court approval process for data collection entirely, opting to simply buy sensitive data from brokers instead of compelling disclosure. The Court’s explicit protection for cellphone location data—and implicit protection for many other types of digital data held by third parties—highlights the importance of addressing this issue.

It should also close the door on arguments that such data are not Fourth Amendment protected. Perhaps even more so than data-sharing features users knowingly accept, data being harvested and funneled to brokers in unexpected and all-too-often unscrupulous ways (such as sensitive location data being stockpiled and sold by a flashlight or prayer app) seems even more acutely to reflect the sentiment of Chatrie that “the exposure of that information to [a company] is merely what happens when a user avails himself of one of the services on his cell phone.”

And if, as is now the law governed by Chatrie, “a cell-phone user is not to be viewed as sharing private information with third parties—which then can be freely passed on to the government—just by doing the ordinary things cell-phone users do,” it makes little sense to say a dispositive and overriding factor should be whether or not the government paid the third party for the data. While the Court did not explicitly address the data broker loophole in its ruling, it does seem to have laid the foundation for closing it.

However, it's unfortunately unlikely that the judiciary will resolve this issue soon. Even as Chatrie bolsters Fourth Amendment protections for digital data, the government will likely continue to rely on other arguments, such as ICE’s spurious claim that purchasing location data tied to Mobile Advertising IDs (which can be de-anonymized) rather than phone numbers nullifies any Fourth Amendment concerns.

There is also a serious practical obstacle: because exploitation of the data broker loophole is cloaked in secrecy, it is difficult to discover particular uses that could then be challenged in court. And if such a challenge did occur, it would take years for litigation efforts to resolve the issue (the geofence warrant at issue in Chatrie that now returns to the circuit court for further evaluation was issued over seven years ago). The faster path would be for Congress to pass legislation such as the Fourth Amendment Is Not For Sale Act.