WASHINGTON, DC — A federal district court ruled last week that government agents must obtain “probable cause” warrants before ordering cellular service providers to turn over records revealing where and when customers used their mobile phones. The decision represented the first time a federal court has weighed in on the issue, which has become of increasing concern for privacy watchdogs.In his ruling, Judge Terrence F. McVerry rejected the government’s argument that cellular service providers could be compelled without a warrant to turn over location data. According to a government brief filed in the case, “records of past credit card transactions will often serve to place a person at a given location at a specific time, yet under established Fourth Amendment law they enjoy no Fourth Amendment protection.”

McVerry’s ruling established guidelines for the types of data government can seize without showing probable cause. Lower courts have expressed concern about a lack of guidance on the issue, especially in the face of increasing evidence the Bush administration is willing to violate a broad range of privacy rights in its prosecution of “the war on terror.”

The case at hand involved an investigation of a suspected drug trafficker. The government sought data related to the suspect’s position, call times and durations. McVerry’s ruling affirmed a lower court’s February ruling.

“This is a great ruling for location privacy and for people who think the government should have probable cause before they track you,” said Jennifer Granick, an attorney with the Electronic Frontier Foundation, told The Washington Post. “People place a certain privacy value on their movements. Whether it’s their movements yesterday or their movements today, it’s the same.

“Most people don’t think that somebody could go back in time and find out where I was or who I was talking to or who was nearby at that same time,” she added. “This is sensitive information, and there should be good reason before the government gets it.”

Other legal experts disagreed with the ruling and Granick’s evaluation of the issues. George Washington University law professor Orin Kerr told the Post the ruling faces “an uphill battle on appeal.” The government already is considering that option, according to a spokesman for the U.S. Department of Justice.