Chatrie: Old Doctrine, New Surveillance
(by Pegah K. Parsi)
Few things are more appropriate on a July 4th weekend than sitting poolside with a cold beverage to dig deep into Supreme Court decisions issued in June. And when a decision concerns privacy rights, all the better! So, it was that I spent my Independence Day reading Chatrie v. United States.
As it is the 250th anniversary of the Declaration of Independence (but not the Constitution, which will celebrate its 250th in 2037), it is helpful to recall a reminder from some of our past statesmen. With apologies to Misters Franklin, Jefferson, and Lincoln for paraphrasing and synthesizing: in order to keep our Republic, we must refresh the tree of liberty from time to time; the dogmas of the quiet past are inadequate for the stormy present. We must think anew and act anew. In Chatrie, the Supreme Court did neither, though it did stick with and expand on precedents that are due for a rethink.
Declaring Independence from Katz
Let’s cover a few things in our time together: In Chatrie, the Supreme Court reached an important result while relying on 4th Amendment doctrines that are increasingly difficult to reconcile with modern technology. Sure, the decision is a welcome victory for privacy, but it also demonstrates the limits of the Court's current Katz framework. This post first reviews the background that led to Chatrie, then summarizes the Court's opinions, argues that Katz's "reasonable expectation of privacy" test and the Third-Party Doctrine have reached the end of their useful lives, and finally provides a proposal to think and act anew.
A primer on the relevant portions of 4th Amendment jurisprudence
The 4th Amendment protects the right of the people to be secure in their persons, houses, papers, and effects against unreasonable searches and seizures. The first step of a 4th Amendment analysis is whether something constitutes a "search," and, if so, whether that search is "unreasonable."
In 1967, in Katz v. United States, the Court expanded the traditional "persons, houses, papers, and effects" to areas and activities where a person has a "reasonable expectation of privacy." The most significant relevant exception that followed about a decade later is the Third-Party Doctrine, established in United States v. Miller (1976) and Smith v. Maryland (1979): a person loses 4th Amendment protections when they voluntarily entrust their information to a third party, say, a bank (Miller) or a phone company (Smith). Bank records and phone call logs, the Court said, are fair game for the government without a warrant.
As digital technologies evolved, that framework became harder to apply. Smartphones, internet services, cloud storage, and countless online platforms all require us to disclose information to third parties simply to participate in modern life. In 2018’s Carpenter v. United States, the Court acknowledged that reality, holding that law enforcement generally must obtain a warrant before acquiring historical cell-site location information from a wireless carrier. Carpenter recognized that prolonged location tracking reveals the whole of our physical movements, making it qualitatively different from the business records at issue in earlier Third-Party Doctrine cases: it is comprehensive, retrospective, and generated without any affirmative act by the user. Carpenter was a landmark, but it left significant questions open, most importantly, how far its reasoning extended beyond cell-site data to other forms of digital location tracking. Chatrie is the Court's first major answer to that question. The question here was whether Google’s Location History, collected through geofence warrants, receives similar 4th Amendment protection.
Chatrie synopsis
The Majority
In Chatrie, the Court said that law enforcement conducted a 4th Amendment search when it acquired cell phone location information. It was a limited, though still important decision, finding that we have a reasonable expectation of privacy in our smartphone Location History stored by Google.
The Court's 6-3 judgment extended Carpenter's protections to geofencing warrants, which compel companies like Google to identify all devices present in a geographic area during a given time window. Justice Kagan, writing for the majority, found that a person has a reasonable expectation of privacy in smartphone Location History because the data functions as a kind of personal journal and because most people think of the information as “ours.” Compared to the cell-site data in Carpenter, Location History is "more the individual's own."
Helpfully, the Court said that the duration of the surveillance was not dispositive, and that it doesn't matter whether the search turns up anything sensitive or intimate. It reiterated that we have a reasonable expectation of privacy in the whole of our movements, even in public. All good stuff.
On the Third-Party Doctrine, the Court said it didn’t apply here because the user didn't really give their data to Google voluntarily; smartphone use is an indispensable part of modern life; and location data are very revealing, comprehensively chronicling our lives' movements. Justice Kagan gets cool nerd points for using the phrase “virtual panopticon” to describe the government’s sweeping access to our activities. Google's notice, the Court added, was neither especially clear nor especially meaningful. This was contrasted with bank and phone records of precedents past and found to be different.
The Court didn’t decide whether the search itself was reasonable or whether the good-faith exception would ultimately permit the evidence to be used. Those questions were left for the lower courts on remand.
Concurrences and dissents
Justice Jackson's concurring opinion, joined by Justice Sotomayor, tackles that question head-on, and would have gone further than the majority. She'd have found that the warrant itself was so defective that officers could not reasonably rely on it in good faith. She correctly points out that the warrant's multi-step design let officers gather increasingly sensitive information without returning to a neutral and detached magistrate for authorization, leaving too much to the discretion of the officers themselves.
Leaving aside that warrants are approved with minimal scrutiny far more often than we'd like to admit, her concurrence also does important work in debunking the concept of "anonymized" data. Officers first received supposedly anonymized location information from Google and later obtained identifying information through the warrant's final step. The process demonstrates how easily “anonymous” datasets can become identified when officers are permitted to narrow the field over time. It is a reminder that none of us should hang our hats on data anonymization, certainly not when it comes to 4th Amendment protections.
Justice Gorsuch agreed that the majority had exposed weaknesses in existing doctrine. As in prior cases, he argued that Katz's reasonable expectation of privacy test lacks any meaningful constitutional foundation. Rather than relying on reasonable expectations, he would ground 4th Amendment protections in traditional property rights.
The dissents split from there. Justice Barrett did not quarrel with Carpenter itself. She agreed with the majority's framework but concluded that Chatrie voluntarily disclosed his Location History by opting into Google's service. Justice Alito, joined in part by Justice Thomas, argued that the decision would significantly reshape 4th Amendment doctrine while suggesting that Chatrie might ultimately lose anyway because the good-faith exception could still apply.
A privacy victory built on increasingly unstable doctrine
The result in Chatrie is welcome; the reasoning is less satisfying.
The Court seems determined to preserve its older precedents while reaching outcomes those precedents increasingly struggle to support. At times, it feels as though the opinion twists itself into a pretzel trying to distinguish Google's Location History from the bank records and telephone records that past, inconvenient precedents placed within the Third-Party Doctrine.
Consider the Court's emphasis on necessity. It reasons that we don’t really, really volunteer our location information because smartphones are indispensable to modern life. Fair enough. But it is difficult to see why that logic would not also apply to bank records or phone logs. Location History (of which I have opted out, thank you very much) is arguably less indispensable than having a bank account (no, I’m not a good candidate for “unbanking”). My apps may not work particularly well without location tracking turned on, but my bank definitely won’t work if I don’t, you know, have transaction records. And my phone's call records, which I have no choice over, are similarly a necessary part of having a phone line.
Let's spend a minute on choice. SCOTUS precedent says that bank records and phone logs (but not cell tower pings) fall under the Third-Party Doctrine because we voluntarily use those services knowing our data will end up in someone else's hands. Here, the Court says our data isn't really given to Google voluntarily if we're using the smartphone the way a smartphone is meant to be used; using an app-based phone the way people actually use one requires sharing data with Google. And Google's notice, which lacked specificity and was arguably manipulative, wasn't enough to turn Location History into a voluntary disclosure of data.
Now, many people (looking at you, CIPA plaintiffs) are reading this as the death knell of, or at least a warning to, pervasive "consent"-based processing. I don't see this opinion as that broad. The Court does seem to say we can't just click away our 4th Amendment rights on an app-by-app basis, but, as much as we may wish it were so, it doesn't yet seem to go so far as to strike a blow at the very way the internet seems to work these days. It also doesn't seem to extend beyond the 4th Amendment context into consumer protection more generally. Not yet, anyway. That’ll take a few more cases and a more willing Court. It took a few decades just to get to Carpenter.
Which brings me to this point about Location History being "more the individual's own": Google readily uses location data for its own advertising purposes and to build commercial profiles and run behavioral analytics for others to use. Beyond opting in or out of Location History altogether, whatever choice we do have tends to be opaque and notoriously hard to find. We tend to feel more ownership over our emails and photos on Google than we do our Location History, because it is collected quietly in the background and Google and friends do so much other stuff with it.
The comparison to bank records is similarly less clear-cut than the Court suggests. While our bank records aren't a comprehensive chronicle of our lives, they certainly paint a good picture. I use my bank records to do my taxes, remember where I donated money last year, check how much I paid for my prescriptions last month, recall the name of that one restaurant, and scold myself for, once again, not sticking to my budget. The fact is that, for both practical and historical purposes, bank records can be remarkably revealing.
Justice Gorsuch started out well enough, pointing out that the distinctions between Google Location History and other types of information the Court has found subject to the Third-Party Doctrine were pretty thin. He has long been skeptical of Katz; the "reasonable expectation of privacy" standard, he argues, isn't workable and isn't rooted in anything in the Constitution. I agree with him there.
But then he takes a different route, arguing that privacy rights should be tied to one's bundle of property rights (possession, disposition, exclusion, and so on) in one's papers and effects. Now I'm unpersuaded. The problem is that a property-rights framework excludes exactly what most needs protecting: our movements, our associations, our location in public, our activities that don't create a discrete record, our data available for purchase through data brokers (the big loophole that still remains), and our data collected en masse as part of a dragnet. These don't map naturally onto a property-rights analysis, especially when they're billed as "anonymized" or when they're swept up alongside everyone else's records. Tying privacy protections to property rights limits what should be protected.
Separately, the Katz-Chatrie line still leaves us exposed on some of our most invasive surveillance systems, like networked license plate readers and AI-enabled camera systems (I see you, Flock). Courts have mostly let these through so far, reasoning that individual captures are just momentary glimpses of a car in public view, nothing like the comprehensive record in Chatrie. Whether that reasoning survives contact with a networked system that can reconstruct weeks of someone's movements is genuinely up for grabs: a federal court sided with Flock's Norfolk, Virginia network on exactly that theory in January 2026, and the case is now on appeal. But that's exactly the problem. Under Katz, the answer turns entirely on how a court happens to characterize the technology, a series of momentary public glimpses, or a comprehensive record, and reasonable courts are already splitting on it.
Justice Gorsuch is right about one thing: Katz's time has probably come. I simply do not think his replacement is the right one.
If not Katz, then what?
Two things are simultaneously true about privacy: 1) it is fundamental, foundational even, to personhood, the acquisition of knowledge, social movements, healthy markets, and democracy, and 2) our privacy sensitivities — what we consider reasonable — tend to ebb and flow depending on the goings-on of the day, our personal circumstances, and the specific privacy stakes at hand (bodily, territorial, communication, or data privacy, for example).
Once upon a time, privacy sensitivities were low when toileting was a semi-public activity (still the case in parts of the military!). They are low when we live in close quarters. They are low at the nude beach. They are low on TikTok. They are lower for part of the population during emergencies like 9/11 or a pandemic; they are higher for other parts of the population during the exact same emergency. They are high when someone invents a transformative technology, like the camera… or AI. They are high if we wear a hijab.
The reasonable standard is indeed no good anymore. What we consider reasonable changes. It leads people to say silly things like "there is no expectation of privacy in public" even as AI systems follow us through public spaces, analyze our behavior, identify our associations, and construct comprehensive profiles of our daily lives. Majority sensitivities at a given moment should not determine whether something is worthy of 4th Amendment protection.
The Third-Party Doctrine is also old and unworkable. Everything we do online or on a smartphone (an “indispensable part of modern life,” as the Court says) requires us to give our information to a third party, sometimes many, many third parties we've never heard of. We can't bank or browse or shop or doom-scroll or date online without our data being harvested, used, and reused, mostly without our understanding. (It is here that I renew my perpetual call for a new business model that doesn't require all this. There used to be a world that didn't require everything about me for the sake of selling me a smart shoe! Now, get off my lawn!)
What actually seems impossible these days is living a modern life without giving data to some third party (let's not even get into the AI conversation). And the wall we still imagine separating private industry from the government? Well, that wall is porous and free-flowing. No warrants required.
Let's retire both the reasonable-expectation framework and the Third-Party Doctrine. Katz was right that there was something more worthy of protection than mere "persons, houses, papers, and effects," but it was wrong to make the scope of that protection depend on fluctuating social expectations. Justice Gorsuch is likewise right that the doctrine needs a firmer constitutional foundation, but grounding privacy entirely in property rights leaves too much unprotected. Our movements, associations, beliefs, and activities do not always map neatly onto traditional property concepts.
Instead, let's develop a jurisprudence built on the importance of privacy to all our other activities, rights, and needs in a liberal democracy. The question we should ask is: Does government access to this information substantially burden the exercise of other constitutional liberties, threaten the personal autonomy that makes those liberties meaningful, or undermine the conditions necessary for democratic self-government?
Privacy is not valuable merely for its own sake. We value it because it enables everything else. It enables free speech. It enables religious exercise. It enables political association. It enables property ownership. It enables intellectual exploration and loafing about as we see fit. It enables personal autonomy. Without meaningful privacy, each of those freedoms becomes easier to monitor, discourage, or manipulate. Without privacy, we erode all our rights over time.
Let’s go back to Flock as an example. Under Katz, the answer turns on whether a court is willing to call a single license-plate photo a "search," one camera at a time. Under this test, the question is simpler: does a networked system that can reconstruct someone's movements over weeks burden their ability to associate, worship, or seek medical care without the government watching? For a system built to answer exactly that question, the answer is yes, and it doesn't depend on parsing whether any single photograph was "voluntary" or whether the data were considered one’s "own."
If privacy is fundamental to the exercise of our First Amendment rights, our property rights, and our right to personhood, then let's protect those activities and data that give maximum effect to those rights. The whole of your movements and associations over extended periods of time (like the kind Flock captures), your bank records, your health information, your religious affiliations, what you do in your home, and your protest activities (yes, even in public!) are all fundamental to supporting your other constitutional rights. That is so even if society's current sensitivities to a specific privacy issue have waned for a bit, and it will remain so when everyone is up in arms about their privacy rights. Say it with me now: Majority sensitivities at a given moment should not determine whether something is worthy of 4th Amendment protection. This way of thinking about privacy in general, and about the 4th Amendment in particular, lets us apply the values of a liberal democracy to any new technology or methodology that comes along, while still giving discretion and flexibility to the judiciary.
Would this framework be perfectly clean and easy? Of course not. Neither is the one we have. But, to address Justice Gorsuch's concern that the reasonable-expectations standard isn't rooted in anything, it would ground privacy doctrine in enduring constitutional values rather than shifting public attitudes or increasingly artificial distinctions about whether we technically "shared" information with someone else.
The dogmas of the quiet past are indeed inadequate for the stormy present. That, to me, is what thinking anew and acting anew looks like. It remains faithful to the Constitution while giving courts a framework capable of addressing whatever technologies come next.
After all, we value privacy precisely because it enables all the other things we need in a healthy democracy.
Now, off to see some 250th fireworks.
ED note: on July 14, 2026, Newport, KY terminated its Flock ALPR pilot in part due to concerns regarding Chatrie. https://www.wcpo.com/news/northern-kentucky/newport-to-remove-flock-cameras-end-pilot-program
Pegah K Parsi is a privacy attorney and advocate. Besides consulting on law enforcement impacts on privacy, she works on education, research, and health privacy. Pegah previously served two terms as Vice-Chair on the City of San Diego’s Privacy Advisory Board.