Cell phones and the apps they use collect GPS data that continually records the movements of the phone—and its owner. This location data, which can show with precision where a cell phone user has been every moment over the course of years, can be stored by companies like Google. In the past decade, courts have begun approving police requests for so-called “geofence warrants,” which require these companies to turn over the location history and identities of people whose phone was near a specified place within a specified timeframe.

In this case, the use of a geofence warrant identified Okello Chatrie as a suspect in a bank robbery, leading to his conviction. Challenging that conviction, Chatrie argued that the geofence warrant violated the Constitution’s Fourth Amendment, which protects against unreasonable searches and seizures. The district court agreed that the geofence warrant violated the Constitution, but held that the resulting location data should not be excluded from the case. The United States Court of Appeals for the Fourth Circuit, sitting en banc, agreed that the location data should not be excluded. Chatrie then petitioned the Supreme Court, which agreed to hear the case.

In March 2026, the Constitutional Accountability Center filed an amicus brief urging reversal of the Fourth Circuit’s decision, explaining why the Fourth Amendment applies to geofence warrants and why such warrants fail to satisfy its requirements.

As we explain, when courts are determining whether a government acquisition of information like GPS data is a “search” regulated by the Fourth Amendment, courts must take into account the ways that revolutionary surveillance capacities like GPS tracking threaten the security of “the people” against arbitrary government power. The Fourth Amendment’s text does more than ban unreasonable searches and seizures—it explicitly guarantees “the people” the right “to be secure” against them. That broad wording was a deliberate choice, reflecting the Framers’ concern that unchecked search authority magnified the power of the government over the populace by permitting officers to intrude on people and their property arbitrarily or abusively.

We further explain why allowing the government unsupervised access to cell phone GPS data would violate the people’s right to be secure in their persons and possessions. Modern technology like geofencing has given the government new ways to intrude on the privacy of people and property. Location information generated by a person’s own phone reveals comprehensive details about that person’s whereabouts, including inside his or her home. And everyone with a cell phone is vulnerable to law enforcement’s exploitation of this data, which can retrace a person’s every movement years after the fact. Allowing the government to access everyone’s GPS phone data without judicial oversight would therefore undermine the people’s right to be secure in their persons and property.

We also discuss why the right to be secure calls for clear rules that let the people know when the government can acquire their information outside of Fourth Amendment constraints. When new digital surveillance tools are at issue, courts should not rest their decisions on case-specific details like the amount of data collected in a particular case or the terms of a particular company’s customer agreements. Only bright-line rules can give the people the clarity they need. Here, because of the intrusiveness of GPS tracking and its capacity to facilitate mass surveillance, any government acquisition of GPS phone data should be regulated by the Fourth Amendment.

Finally, we explain why the right to be secure calls for a strict approach to the Fourth Amendment’s requirements that warrants be particularized and supported by probable cause. To avoid giving government officers the excessive discretion the Framers tried to avoid, courts cannot treat a massive database containing millions of users’ records as a single “place” to be searched under one warrant, and police should not be allowed to single out particular users for scrutiny without judicial approval.