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The next legal battle (or three) over location tracking

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  1. Policy
A 2018 Supreme Court decision has not settled the law on the warrantless seizure and search of cell phone records.

You might have been under the impression that the U.S. Supreme Court resolved how the Fourth Amendment applies to cell phone location data in 2018, when it decided Carpenter v. United States, a case concerning the warrantless seizure and search of cell phone records. (The Reporters Committee filed a friend-of-the-court brief in Carpenter to explain why location tracking also implicates First Amendment values, including reporter-source confidentiality.) If you want someone’s data, the justices concluded in that case, go get a warrant. So far, so simple. But developments since Carpenter have made clear that settled law settles very little.

The Department of Homeland Security maintains, for instance, that the warrant requirement doesn’t apply when the agency buys Americans’ location information from a data broker, according to a memo recently obtained by BuzzFeed News. Which, given what’s available for sale these days, makes for quite the constitutional loophole.

The Department argues that individuals have no reasonable expectation of privacy in location information “provided to a third-party with a user’s consent.” The “consent” in question, though, will often have been the user’s decision to click “I agree” on a mobile app’s tiny and inscrutable terms of service. Given the Department’s troubling misuse of its existing authorities to monitor journalists, these broad legal claims can’t help but raise concerns about how those commercial datasets will be deployed.

Who’s to say, meanwhile, that a warrant requirement is enough to prevent dragnet location monitoring? That’s the question presented by a string of recent court decisions involving “geofence warrants.” In each of these cases, rather than serve a court order that asked for location data corresponding to a known phone, police asked for the opposite — for information on all of the devices that were in a particular location at a particular time. Of course, the results can expose sensitive interactions that have nothing to do with the crime police are investigating: a doctor’s visit, say, or a reporter’s interaction with a confidential source.

These warrants have drawn scrutiny from privacy advocates because, well, they don’t really do the thing a warrant is expected to do: prevent the government from invading the privacy of individuals the government has no reason to suspect of a crime. For just that reason, organizations like the Electronic Frontier Foundation argue these “reverse warrants” violate the Fourth Amendment. But magistrate judges have divided on the question, and no appeals court has weighed in. As a result, it remains unclear whether this increasingly popular law enforcement tool is legal.

As path-breaking as it might have been, then, whether Carpenter can meaningfully protect location privacy along with all its associated constitutional values will turn on questions the justices have yet to answer.


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The Technology and Press Freedom Project at the Reporters Committee for Freedom of the Press uses integrated advocacy — combining the law, policy analysis, and public education — to defend and promote press rights on issues at the intersection of technology and press freedom, such as reporter-source confidentiality protections, electronic surveillance law and policy, and content regulation online and in other media. TPFP is directed by Reporters Committee attorney Gabe Rottman. He works with Stanton Foundation National Security/Free Press Legal Fellow Grayson Clary and Technology and Press Freedom Project Legal Fellow Mailyn Fidler.