Legal authorities do not need a warrant to obtain records detailing a cellphone's location, a federal appeals court in New Orleans has ruled, overturning a trial judge who said subscribers enjoy a Fourth Amendment privacy interest in the data.

A divided U.S. Court of Appeals for the Fifth Circuit ruling on Tuesday marked a major win for the U.S. Justice Department, which fought to salvage the ability of federal agents to obtain historical cell site location data via a court order, instead of a warrant under the higher probable-cause standard.

The ruling marked the first time a federal appellate court took up the closely watched issue, and it's sure to pop up in the U.S. Court of Appeals for the Fourth Circuit, which is preparing to hear a dispute over law enforcement's ability to retrieve cell tower data from wireless telecommunications companies.

Court orders for cell site location data under the Stored Communications Act, the Fifth Circuit panel majority said, are not unconstitutional. The court said the information—which includes the date, time and location of a phone call—constitute a business record that belongs to the telecommunications provider. The government is not required to give notice to the subscriber.

Judge Edith Brown Clement, writing for the majority, rejected concerns that the executive branch, without having to seek a warrant, would in effect be policing itself. The court, wrote Clement, joined by Senior Judge Thomas Reavley, "has difficulty understanding this fear."

"If the official executes the order improperly, an injured party may seek judicial review of his actions," Clement wrote. "These safeguards adequately protect against executive overreaching."

The case was rooted in government applications, filed in 2010 in the U.S. District Court for the Southern District of Texas, for evidence in three separate criminal investigations. U.S. Magistrate Judge Stephen Smith concluded that "compelled warrantless disclosure of cell site data violates the Fourth Amendment." A federal trial judge upheld that conclusion.

Mobile phone use, Clement said, is voluntary and subscribers understand that devices must connect to a cell tower to make a call. The court rejected the argument by the American Civil Liberties Union, participating as a friend of the court, that mobile users do not directly transmit cell site information. (The only direct information a user provides, the ACLU said, is the phone number dialed.)

Clement called the ACLU argument a "crabbed" understanding that would create "absurd" results. The judge crafted a hypothetical scenario in which a subscriber uses speed dial to contact another person.

"Would that mean that the Government would be unable to obtain the contact's actual telephone number from his service provider?" Clement wrote. "Clearly not."

Clement said the court understood that cellphone users "may reasonably want their location information" to remain private.

"But the recourse for these desires is in the market or the political process: in demanding that service providers do away with such records (or anonymize them) or in lobbying elected representatives to enact statutory protections," Clement wrote. "The Fourth Amendment, safeguarded by the courts, protects only reasonable expectations of privacy."

The ACLU's Catherine Crump called the ruling "troubling." The ACLU and the Electronic Frontier Foundation, Crump said, argued in the case that only a warrant standard fully protects Americans' privacy interests in their locations and movements over time."

"Given the sensitivity of these facts, law enforcement agents should have to demonstrate to a judge that they have a good reason to believe that they will turn up evidence of wrongdoing before gaining access to information that can paint a detailed picture of where a person has been over time," Crump wrote in an ACLU blog post.

Writing in dissent, Judge James Dennis said magistrate judges should require the government to obtain a warrant for cell site data under the Stored Communications Act itself, not the Fourth Amendment. "Non-consensual, warrantless compulsion of customer cell site location records raises serious and debatable constitutional question," he wrote.

Perkins Coie senior counsel Mark Eckenwiler, a former top Justice Department lawyer who specializes in electronic surveillance law, called the ruling a "hands down win for the government." Still, the court, did express limits to the reach of the opinion, Eckenwiler noted.

For instance, the panel declined to address a situation in which the government "surreptitiously installs spyware on a target's phone or otherwise hijacks the phone's GPS, with or without the service provider's help." Neither did the court address "orders requesting data from all phones that use a tower during a particular interval," he said.

"In the grand scheme of things, the ruling may be overtaken by something that Congress does," Eckenwiler said. "Congress may decide that all geolocation information requires a warrant."

In a blog post at Volokh Conspiracy, Orin Kerr, who contributed an amicus brief addressing procedural issues, described the case as "a big win for the government." Kerr said the court was correct.

"Meanwhile, we'll see if other circuits agree," wrote Kerr, a Fourth Amendment scholar who teaches at The George Washington University Law School.