We’re Asking the Ninth Circuit to Hold Reverse Location Warrants Categorically Unconstitutional

The Ninth Circuit is about to confront a fundamental question of digital privacy: whether “reverse location warrants,” the sweeping subpoenas that compel telecom companies to hand over the real‑time location of every device within a defined geographic area, violate the Constitution. On the same day that the American Civil Liberties Union and the Electronic Frontier Foundation filed a joint amicus brief in United States v. Spurlock, they asked the court to strike down these warrants as categorically unconstitutional, arguing that they trample on the Fourth Amendment’s protection against unreasonable searches and on the First Amendment’s guarantee of free association.

What Happened

In the Spurlock case, federal prosecutors sought a “tower dump” warrant—an order that required a cellular carrier to provide the location data of every phone that connected to a specific cell tower during a three‑day window surrounding a robbery. The government argued that the warrant was a lawful investigative tool, akin to a traditional “pen register” that records numbers dialed. The district court granted the request, and the defense immediately challenged the order, asserting that the blanket collection of location data amounted to an unreasonable search.

The appeal landed on the Ninth Circuit, marking the first time a federal appellate court has been asked to rule on the constitutionality of reverse location warrants. The ACLU and EFF’s amicus brief emphasizes that the warrant’s breadth—capturing the movements of innocent bystanders who had no connection to the alleged crime—runs afoul of longstanding privacy jurisprudence. Their filing also points to the Supreme Court’s decision in Carpenter v. United States, which recognized that historical cell‑site location information (CSLI) is protected by the Fourth Amendment.

While the government maintains that the warrant is narrowly tailored to a specific investigative need, critics argue that the “tower dump” is a blunt instrument that indiscriminately harvests data on thousands of unrelated citizens, effectively turning the nation’s wireless infrastructure into a surveillance net.

Key Details

The Spurlock warrant demanded the carrier’s complete logs for a single tower covering a radius of roughly one mile, encompassing an estimated 12,000 active devices. The data request included timestamps, signal strength, and triangulated coordinates for each device, creating a detailed map of every person’s movements during the specified period. The brief notes that the government’s justification relied on a vague “probable cause” assertion, despite the fact that no specific suspect had been identified at the time the warrant was issued.

Legal scholars cited in the brief argue that the warrant violates the Fourth Amendment’s particularity requirement. The Constitution demands that a warrant describe the “place to be searched, and the persons or things to be seized.” A reverse location warrant, by its nature, fails to specify any individual suspect, instead sweeping up data on an entire population. Moreover, the brief highlights that the warrant bypasses the traditional “probable cause” standard by allowing the government to obtain data without first demonstrating a concrete link between any device and the crime.

Beyond the Fourth Amendment, the brief raises First Amendment concerns. By revealing the whereabouts of individuals engaged in lawful assembly, political protest, or religious worship, the warrant creates a chilling effect that deters free expression. The authors point to recent cases where law enforcement used location data to track civil‑rights activists, underscoring the potential for abuse when the state can monitor entire communities without individualized suspicion.

Background

Reverse location warrants emerged in the early 2010s as law‑enforcement agencies sought to adapt traditional surveillance techniques to the digital age. Unlike a conventional search warrant that targets a specific person or property, a reverse location warrant compels a service provider to disclose the location of every device that connected to a particular cell tower or set of towers during a defined timeframe. Proponents argue that such warrants are indispensable for rapidly evolving investigations, especially in cases involving mass shootings or coordinated terrorist attacks.

However, the legal landscape has shifted dramatically since the Supreme Court’s 2018 Carpenter decision, which held that accessing historical CSLI requires a warrant supported by probable cause. While Carpenter dealt with data held by the government, reverse location warrants ask providers to surrender data that has never been accessed by law enforcement, raising novel constitutional questions. The Ninth Circuit’s upcoming decision will be the first appellate ruling to directly address whether the broad, non‑targeted nature of these warrants is permissible under the Fourth Amendment.

Why It Matters

At stake is the balance between public safety and individual privacy in an era where smartphones have become extensions of the self. If the Ninth Circuit upholds the legality of reverse location warrants, it could legitimize a surveillance regime that permits the government to map the movements of entire neighborhoods with minimal judicial oversight. Such a precedent would likely spread to other circuits, creating a patchwork of permissive standards that erode privacy protections nationwide.

Conversely, a ruling that declares these warrants unconstitutional would reinforce the principle that the government must obtain a warrant that is both particularized and supported by probable cause before intruding on the digital footprints of ordinary citizens. It would also send a clear signal to Congress and law‑making bodies that any future legislation authorizing mass location data collection must meet strict constitutional safeguards, thereby preserving the core freedoms enshrined in the Bill of Rights.

What Happens Next

After oral arguments, the Ninth Circuit will issue an opinion that could either affirm the district court’s grant of the warrant or reverse it on constitutional grounds. If the court sides with the government, the decision will likely be appealed to the Supreme Court, where it could become a landmark case defining the limits of digital surveillance. Advocacy groups are already preparing for a potential petition for certiorari, emphasizing the broader implications for privacy across all federal circuits.

Regardless of the outcome, the case has already sparked legislative interest. Several state legislators have introduced bills that would either prohibit reverse location warrants or require a higher standard of proof before such data can be accessed. Lawmakers at the federal level are also monitoring the case, with some members of Congress proposing amendments to the Stored Communications Act to explicitly ban indiscriminate location data collection. The coming months will reveal whether the judiciary, the legislature, or a combination of both will ultimately shape the future of reverse location warrants.

The Spurlock case represents a pivotal moment in the ongoing struggle to protect digital privacy against expanding government surveillance powers. By asking the Ninth Circuit to deem reverse location warrants categorically unconstitutional, the ACLU, EFF, and their allies are drawing a line in the sand: privacy cannot be sacrificed on the altar of convenience, even in the pursuit of public safety. The court’s decision will reverberate far beyond a single robbery investigation, setting a precedent that will define how Americans’ movements are monitored—and protected—for generations to come.