This week and last, the Cato Institute filed amicus briefs urging the Supreme Court to take up two cases dealing with the constitutional status of “cell site location information,” or “CSLI.” This data, collected of necessity by cellular communications providers, creates detailed records of their customers’ movements. The briefs invite the Court to accept these cases so it can revise Fourth Amendment practice to eschew doctrine and more closely adhere to the language of the Fourth Amendment.

The Fourth Amendment states that “[t]he right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated.” Presumably, when called upon to determine whether a Fourth Amendment violation has occurred, courts would analyze the elements of this language as follows: Was there a search? Was there a seizure? Was any such search or seizure of “their persons, houses, papers, [or] effects”? Was any such search or seizure reasonable?

And in cases involving familiar physical objects, courts usually do a sound textual analysis, at least implicitly. But in harder cases dealing with unfamiliar items such as communications and data, courts retreat to “reasonable expectation of privacy” doctrine that emerged from Katz v. United States in 1967, and offshoots of it like the “third‐​party doctrine.” The “reasonable expectation of privacy” test asks whether defendants’ feelings about things government agents accessed were reasonable. The corollary “third‐​party doctrine” cancels Fourth Amendment interests in information and things that are shared on the theory that expectations of privacy evaporate in that context.

The “reasonable expectation of privacy” test is the product of one non‐​essential concurrence in Katz, and the third‐​party doctrine was wrong when the Supreme Court created it in 1976 to ratify a law that deputized banks into financial surveillance. That doctrine grows further out of synch with each step forward our society takes in modern, connected living. Today, third‐​party service providers collect incredibly deep reservoirs of information about us: Cellular telephone networks, Internet service providers, search engines, and payment systems have data that can throw open windows onto our relationships, feelings, health conditions, business dealings, sexuality, emotions, and more.

In United States v. Carpenter, the U.S. Court of Appeals for the Sixth Circuit turned aside the appeal of two men convicted of armed robbery, whose CSLI had been used as evidence against them. Relying most heavily on an application of the “reasonable expectation of privacy” test in Smith v. Maryland, the court said that, while the contents of communications are protected by the Fourth Amendment, routing information is not. The court backhandedly dismissed the crucial question of whether the defendants had a property right in the data the government had seized, even though contracts and regulation both allocate property rights in data about communications use to consumers.

And in a similar case, Graham v. United States, the Fourth Circuit held that CSLI isn’t constitutionally protected because “an individual enjoys no Fourth Amendment protection ‘in information he voluntarily turns over to [a] third part[y]’ ” (quoting Smith v. Maryland).

Rather than relying on misshapen precedent as the appeals courts did, the Supreme Court should find that communications and data are items that can be seized and searched. Consistent with precedents both longstanding and recent, the Court should recognize that telecommunications customers can have property rights in such data, and that when the government seeks to seize and search such data, it generally requires a warrant. This will permit courts below to address seizures and searches of communications and data forthrightly, confidently assessing the reasonableness of government searches and seizures even when communications and data are involved.

The briefs join a merits brief filed this summer in United States v. Benbow, a CSLI case pending in the D.C. Circuit.