Today we received good news for everyone who carries a cell phone — the court of appeals will not reconsider its opinion earlier this year holding that judges may require the government to get a warrant and establish probable cause to obtain historical cell phone location information.

Although few people realize it, cell phone companies keep records of where their customers have been in the past. Law enforcement frequently seeks this information in its investigations, and argues that it need not establish probable cause. They argue that so long as they show the location information is relevant and material to an ongoing investigation — a far lower standard — they are allows to obtain it.

Earlier this year, after receiving briefing from the ACLU and other organizations (ACLU of Pennsylvania, Electronic Frontier Foundation, Center for Democracy and Technology), the court of appeals in Philadelphia held that although the government can obtain this information on a less-than-probable-cause standard in many cases, judges have the discretion to require a warrant, particularly where such information threatens to violate individuals' Fourth Amendment right to be free from unreasonable searches and seizures.

The ACLU believes that a person's movements paints an intimate portrait of their lives, and that particularly as technology evolves and cell phone tracking becomes more accurate, the Fourth Amendment requires the government to obtain a warrant and show probable cause to access such information.

Today's order from the court of appeals, standing by its earlier ruling, is a victory for our privacy. People should not have to choose between being part of the modern world and using technologies such as cell phones, and preserving their privacy.