In November, a federal court in Texas found that the Constitution requires the government to get a warrant and show probable cause before getting access to someone’s historical location data from their mobile carrier. We applauded this decision because cell phones are tracking devices we carry around in our pockets. Knowing where someone goes can reveal a great deal of personal and private information about them – exactly the sort of information the Fourth Amendment was designed to protect.
The government appealed that decision. Last Friday, the ACLU, the ACLU of Texas and the Electronic Frontier Foundation filed a friend-of-the-court (PDF) brief asking the court to uphold the earlier decision. Our brief argues the government should have to go to a judge for a warrant and prove that it has probable cause before getting historical location data.
This is part of our ongoing campaign to make sure that as technology advances, our privacy rights are not left behind. 
