American Civil Liberties Union (ACLU) affiliates in 34 states across the U.S. have filed public records requests seeking information from law enforcement agencies as to when, why and how they are using cell phone location data to track Americans.

“The ability to access cell phone location data is an incredibly powerful tool and its use is shrouded in secrecy. The public has a right to know how and under what circumstances their location information is being accessed by the government,” said Catherine Crump, staff attorney for the ACLU Speech, Privacy and Technology Project.

“A detailed history of someone's movements is extremely personal and is the kind of information the Constitution protects.”

The ACLU wants to know whether the 379 law enforcement agencies demonstrate probable cause and obtain a warrant to access cell phone location data, how frequently they obtain cell phone location data, the amount of money spent on tracking cell phones and other polices related to acquiring location data.

The Geolocation, Privacy and Security (GPS) Act has been introduced to the U.S. House and Senate. The bill would require law enforcement to show probable cause and get a warrant before acquiring geolocational information and create criminal penalties for secretly using an electronic device to track a person’s movements. It would also prohibit businesses from sharing customers’ geolocational information with third parties without the customer's consent.