An Atlanta-based federal appeals court ruled Wednesday that police need a warrant before acquiring Americans’ cellphone location data.

The decision from a three-judge panel of the U.S. Court of Appeals for the 11th Circuit doesn’t apply outside Alabama, Georgia and Florida, but it’s a major development in the nationwide legal fight over applying the Fourth Amendment to electronic data.

The court found police violated the constitutional rights of Quartavius Davis, convicted in 2012 of committing a string of 2010 robberies and sentenced to nearly 162 years in prison, by acquiring his cellphone location data from a service provider without a warrant based on probable cause.

Police instead used a court order based on a lower legal standard, claiming reasonable grounds to believe the records were relevant to a criminal investigation.

“While committing a crime is certainly not within a legitimate expectation of privacy, if the cell site location data could place him near those scenes, it could place him near any other scene,” the judges ruled, finding a warrant was required for such data. “There is a reasonable privacy interest in being near the home of a lover, or a dispensary of medication, or a place of worship or a house of ill repute.”

American Civil Liberties Union staff attorney Nathan Freed Wessler argued the cell tracking part of the appeal on behalf of the ACLU and allied advocacy organizations. He tells U.S. News the ruling likely extends beyond the acquisition of records from phone companies.

Police use of Stingrays – suitcase-size machines that acquire cellphone data by pretending to be transmission towers – is likely also affected, he says.

Much is currently unknown about how police use Stingrays, manufactured primarily by Harris Corporation, and what court approval police seek before using them. But in Florida, surprising details are beginning to emerge.

Tallahassee police, for example, harvested Stingray data at least 200 times without court approval because of a nondisclosure agreement with the device manufacturer, a November 2013 state court ruling revealed. In Sarasota, the U.S. Marshals Service swooped in earlier this month to seize Stingray records after local police agreed to show them to the ACLU.

“The opinion obviously isn’t talking directly about Stingrays, but its logic and holding should apply,” says Wessler. “Police should be on notice now [that they need a warrant] when they use a Stingray."

Wessler expects the U.S. Supreme Court to evaluate constitutional protection for cellphone location data within the next few years. At least two other federal appeals courts are weighing similar cases, he notes.

The 11th Circuit judges addressed Fourth Amendment jurisprudence at length in their ruling, chronicling the evolution of protection from warrantless seizure of records from property-based to privacy-based rationales.

The court leaned heavily on the Supreme Court’s 2012 U.S. v. Jones decision, which found police need a warrant to track a suspect’s movements using a GPS device. The appeals court judges noted that the four-justice Jones majority rested on physical trespass grounds, but that a concurrence from Justice Sonia Sotomayor pondered and a separate opinion by four other justices asserted a Fourth Amendment violation on privacy grounds.