On Wednesday, the Supreme Court heard what could become the most important electronic-privacy case of the 21st century. The justices considered whether the government, without a warrant, can effectively trace our movements in public for months on end by demanding 127 days of the geolocational data—known as cell-site location information—that mobile phones beam out 24 hours a day. During the argument, it was encouraging to see two justices with very different perspectives—Justices Sonia Sotomayor and Neil Gorsuch—make passionate arguments for why allowing these kinds of mass searches of our digital effects would be as invasive and unreasonable as the hated general warrants that helped spark the American Revolution. It’s possible, therefore, that Carpenter v. United States may continue a welcome recent trend: Liberal and conservative justices on the Court, by broad bipartisan margins, are insisting on translating the Fourth Amendment to the Constitution into the digital age.

Justice Elena Kagan framed the stakes in the case by asking Michael Dreeben, the deputy solicitor general, how this case was different from United States v. Jones, a 2012 case where the government tracked a suspect for a month without a warrant by clamping a Global Positioning System device on the bottom of his car. Five justices, led by Justice Antonin Scalia, said that the police violated the suspect’s property rights by committing a physical trespass for the purpose of collecting information—they walked onto his driveway and physically seized his car. But, as Kagan noted, four different justices, led by Justice Samuel Alito said that, even without physical trespass, “society’s expectation has been that law enforcement and others would not, and indeed in the main simply cannot, monitor and catalogue every single movement of an individual’s car for a very long period.” How, Kagan asked, was this case different than Jones?

Dreeben responded that the Jones case involved government surveillance in public, while in this case, the government was seizing business records that individuals had voluntarily turned over to their third-party cellphone carriers, who stored them in the digital cloud. A 1979 case called Smith v. Maryland held that individuals have no expectation of privacy in the telephone numbers they voluntarily surrender to third parties, establishing what is now known as the third-party doctrine.

Kagan was unpersuaded by Dreeben’s attempt to distinguish dragnet surveillance by GPS devices from dragnet surveillance by cellphone tracking. “In both cases, you have reliance on a new technology that allows for 24/7 tracking,” she said. “Now, you’re exactly right, there were different means, but in both cases, you have a new technology that allows for 24/7 tracking and a conclusion by a number of justices in Jones that that was an altogether new and different thing that did intrude on people’s expectations of who would be watching them when.”

At this point, Justice Sonia Sotomayor jumped in. In Jones, Sotomayor wrote an important and prescient analysis of the challenge that confronts the Court as it attempts to translate the Fourth Amendment into a world where our most intimate data is stored not in locked desk drawers, but in the digital cloud. “I for one doubt that people would accept without complaint the warrantless disclosure to the Government of a list of every Web site they had visited in the last week, or month, or year,” she wrote. “I would not assume that all information voluntarily disclosed to some member of the public for a limited purpose is, for that reason alone, disentitled to Fourth Amendment protection.”

In the Carpenter argument, Sotomayor elaborated on her claim in the Jones case that Americans do not expect the government to reconstruct their movements in public and private by seizing electronic data without good reason. She asked Dreeben, “What do you do with the survey mentioned by your opposing colleague that says that most Americans, I still think, want to avoid Big Brother? They want to avoid the concept that government will be able to see and locate you anywhere you are at any point in time.” Sotomayor added, “Do you really believe that people expect that the government will be able to do that without probable cause and a warrant? The Constitution protects the rights of people to be secure. Isn’t it a fundamental concept, don’t you think, that that would include the government searching for information about your location every second of the day for months and months at a time?”

Throughout the argument, Sotomayor gave concrete and convincing examples of how pervasively Americans use their cellphones and how invasive warrantless cellphone tracking could become. “Why is it not okay, in the way we said about beepers, to plant a beeper in somebody’s bedroom, but it’s okay to get the cellphone records of someone who I—I don’t, but I know that most young people have the phones in the bed with them,” she asked to laughter. “All right? I know people who take phones into public restrooms. They take them with them everywhere. It’s an appendage now for some people. If it’s not okay to put a beeper into someone’s bedroom, why is it okay to use the signals that phone is using from that person’s bedroom, made accessible to law enforcement without probable cause?”

In Jones, Sotomayor had suggested that the Court might have to consider its holding in the Smith case that Americans have no expectation of privacy for large quantities of electronic information. “It may be necessary to reconsider the premise that an individual has no reasonable expectation of privacy in information voluntarily disclosed to third parties,” Sotomayor wrote. “This approach is ill-suited to the digital age, in which people reveal a great deal of information about themselves to third parties in the course of carrying out mundane tasks.”  

The lawyer who argued and won Smith v. Maryland in 1979, Stephen H. Sachs, recently suggested in The Washington Post that Smith has “long outlived its suitability as a precedent” because “when the Supreme Court decided Smith, in the pre-dawn of the digital age, we didn’t know about the Internet, smartphones, cloud computing, Facebook, or Twitter.”

In the Carpenter arguments, however, Sotomayor seemed sympathetic to argument of Timothy Carpenter’s lawyer, Nathan F. Wessler, that the Court could rule for his client without overturning Smith entirely, holding that the government may access 24 hours of geolocational data, for example, but not five-months worth of data. As Sotomayor put it:

From the very beginning, Smith, for example, basically said the disclosure at issue doesn’t disclose the content of the conversation … Yet, we drew a line in saying cellphone numbers, telephone numbers are disclosable because everybody knows that the telephone company is keeping track of those numbers. You get it in your phone bill at the end of each month. … That suggests, as you started to say earlier, that it never was an absolute rule, the third-party doctrine. We limited it when … Ferguson when we said police can’t get your medical records without your consent, even though you’ve disclosed your medical records to doctors at a hospital. … So is it really that far off to say, yes, I can believe that my location at one moment or other moments might be searched by police, but I don’t expect them to track me down for 24 hours over 127 days?

It’s heartening that Sotomayor seem ready to limit the scope of the third-party doctrine in cases where the government is trying to reconstruct the movement of citizens over long periods of time. But her approach might not have satisfied Scalia, who wrote in the Jones GPS case that it was the physical trespass on property rights that made 24/7 GPS tracking impermissible.

That’s why the views of Scalia’s successor, Gorsuch, are so important to the disposition of the case. And Gorsuch was just as passionate about the possible Fourth Amendment violation as Sotomayor, because he detected a potential violation of the property rights of cellphone users in the data they turned over to third parties.

Gorsuch signaled his views at the end of the first half of the argument in this exchange with Carpenter’s lawyer:

Gorsuch: Focusing on the property-based approach, putting aside reasonable expectation for just a moment, what do we know about what state law would say about this information?

So say—say a thief broke into T-Mobile, stole this information and sought to make economic value of it. Would you have a conversion—would your client have a conversion claim, for example, under state law? Have you explored that at all?

When Wessler responded that state courts hadn’t explore the possibility, Gorsuch returned to the theme at length in questioning the government’s lawyer, Michael Dreeben:

Gorsuch: Mr. Dreeben, I’d like to—I’d like to drill down on that and return to Justice Kagan’s question. You know, the facts here wind up looking a lot like Jones.

One thing Jones taught us is—and reminded us, really, is that the property-based approach to privacy also has to be considered, not just the reasonable expectation approach.

So, if we put aside the reasonable expectation approach for just a moment, Katz, Miller, Smith, and ask what is the property right here, let’s say there is a property right. Let’s say I have a property right in the conversion case I posited with your colleague. So that if someone were to steal my location information from T-Mobile, I’d have a conversion claim, for example, against them for the economic value that was stolen. Wouldn’t that, therefore, be a search of my paper or effect under the property-based approach approved and reminded us in Jones?

After Dreeben fought the hypothetical, Gorsuch suggested that federal law had already created a property right in the cellphone data by declaring, in section 222 of the Wireless Communication and Public Safety Act of 1999, that “every telecommunications carrier has a duty to protect the confidentiality of proprietary information of, and relating to … customers.” (For an elaboration of the argument that Gorsuch was invoking, read Richard Re and Will Baude’s posts on the Positive Law Model of the Fourth Amendment.) Gorsuch went on to suggest that the Fourth Amendment might prohibit Congress from violating the property right it had created by allowing the data to be seized without a warrant.

Gorsuch: So—so the government can acknowledge a property right but then strip it of any Fourth Amendment protection. Is that the government’s position?

Dreeben: No, no, but I think that the—­

Gorsuch: And so—so could we also say maybe that they also get this property right subject to having a non-Article III judge decide the case, or quartering of troops in your home? Could we strip your property interests of all constitutional protection?

Dreeben: Well, those are pretty far afield. I—I think what’s going on here—

Gorsuch: But does Congress’s determination also yield in the face of the Fourth Amendment, Mr. Dreeben?

Dreeben: It does not.

Gorsuch: It does not. The Fourth Amendment is trumped by this statute?

Dreeben: But what interests the statute —

Gorsuch: In the government’s—in the government's view. Is that—is that right? The statute trumps the Fourth Amendment?

Dreeben: I think I said the opposite.

Gorsuch: Oh, good. All right. I hoped so.

At this point in the argument, Sotomayor enthusiastically endorsed Gorsuch’s argument that Congress couldn’t trump the Fourth Amendment:

Sotomayor: Isn’t what that Congress did?

Dreeben: No, because Congress provided that it shall be disclosed as required by law. And the same Congress has passed—

Sotomayor: Well, but then we—then you’re begging the question, which is Justice Gorsuch’s question, which is what’s the—what does the law, the Fourth Amendment, require in those circumstances?

Dreeben: So this Court has been …

Sotomayor: You’re saying Congress can set the level of what the Constitution requires, but I don't know that that’s true.

And then Gorsuch clinched the point by comparing the warrantless search of private information to the general warrants that sparked the American Revolution:

Gorsuch: Mr. Dreeben, it seems like your whole argument boils down to if we get it from a third party we’re okay, regardless of property interest, regardless of anything else. But how does that fit with the original understanding of the Constitution and writs of assistance?

You know, John Adams said one of the reasons for the war was the use by the government of third parties to obtain information forced them to help as their snitches and snoops. Why—why isn’t this argument exactly what the framers were concerned about?

Chief Justice Roberts invoked the same eloquent analogy in his unanimous opinion for the Court in Riley v. California in 2014, where he quoted John Adams and compared the warrantless search of a cellphone on arrest to the general warrants that sparked the American Revolution. “Modern cellphones are not just another technological convenience,” Roberts wrote. “With all they contain and all they may reveal, they hold for many Americans “the privacies of life. … The fact that technology now allows an individual to carry such information in his hand does not make the information any less worthy of the protection for which the Founders fought.” In the Carpenter argument, Roberts questioned the government’s argument that we voluntarily turn over private data to cellphone companies and therefore abandon expectations of privacy in the data. “That sounds inconsistent with our decision in Riley,” Roberts noted, “which emphasized that you really don’t have a choice these days if you want to have a cellphone.”

As the oral argument revealed, the Supreme Court could decide the Carpenter case narrowly or broadly, and on a range of theories. The conservative justices might hold, with Gorsuch, that Congress has created a property interest in our geolocational data that the Fourth Amendment prevents it from invading it without a warrant. The more liberal justices might hold that we have an expectation of privacy in electronic data that prohibits the government from tracking us over long periods of time, regardless of whether our property rights are invaded. Some justices might even embrace both theories. It is inspiring, in any event, to see justices as diverse as Gorsuch and Sotomayor providing constitutional leadership about the urgent need to translate the Fourth Amendment into an electronic age. By recognizing our privacy and our property interests in being free from unreasonable searches and seizures of our digital effects, the Court can ensure that Americans in the 21st century have the same freedom to be let alone that inspired the 18th-century Framers to fight the American Revolution and to ratify the Bill of Rights.