Just two days after new legislative reform on e-mail privacy was re-introduced in Congress, another privacy bill was brought back from years past.

On Thursday, three members of the House (two Republicans and a Democrat) and two bipartisan senators introduced the GPS Act, which would require law enforcement to obtain a probable cause-driven warrant before accessing a suspect’s geolocation information. The bill had originally been introduced nearly two years ago by the same group of legislators.

As Ars’ Tim Lee wrote in 2012, the Obama Administration laid out its position in a legal brief last year, arguing that customers have "no privacy interest" in cell-site location records (CSLR) held by a network provider. Under a legal principle known as the "third-party doctrine," information voluntarily disclosed to a third party ceases to enjoy Fourth Amendment protection. The government contends that this rule applies to cell phone location data collected by a network provider.

The new GPS bill as it stands (PDF) contains exceptions for emergencies, including "national security" under the Foreign Intelligence Surveillance Act, but otherwise requires a warrant for covert government-issued tracking devices. The proposed penalty for violating this new provision could come with fines and/or five years in prison. The American Civil Liberties Union (ACLU) has also endorsed the new bill.

“Cell phones are also portable tracking devices, and the law needs to catch up with technology to protect Americans from the indiscriminate use of this type of invasive surveillance,” Chris Calabrese, legislative counsel at the ACLU, wrote in a statement.

“Police routinely get people’s location information with little judicial oversight because Congress has never defined the appropriate checks and balances. Under the GPS Act, all that would change. Police would need to convince a judge that a person is likely engaging in criminal activity before accessing and monitoring someone’s location data. Innocent people shouldn’t have to sacrifice their privacy in order to have a cell phone.”