Police officers and federal agents who track Americans' cellphones without a judge’s permission could face up to 10 years in prison if new bipartisan legislation becomes law.

The Stingray Privacy Act, introduced Monday, would require authorities to get a warrant under most circumstances before using cell-site simulators. The devices, commonly known as Stingrays, imitate cell towers to acquire real-time location information and other data from nearby phones.

“The penalty is there as a deterrent,” says Rep. Peter Welch, D-Vt., an original co-sponsor of the bill. ”[But] the warrant requirement is really the most important part and it’s pretty easy to comply with.”

The bill comes following a steady trickle of information about authorities’ use of the devices and about two months after the Justice Department announced it would begin requiring many federal agents – but not state or local law enforcement – to get warrants before using the technology. The new bill would apply to all federal and local authorities.

“The abuse of Stingrays and other cell-site simulators by individuals, including law enforcement, could enable gross violations of privacy,” the bill’s sponsor, Rep. Jason Chaffetz, R-Utah, warned in a statement Monday.

Chaffetz, chairman of the House Oversight Committee, was joined by Welch and Democratic Rep. John Conyers of Michigan as initial co-sponsors, and singled out the use of Stingrays by the Internal Revenue Service as a concern.

The IRS’ use of the devices, revealed by the Guardian last week, “raises serious questions about who is using this technology and why,” he said. “These questions demonstrate the need for strict guidelines that carry the weight of the law."

But some see the proposed legal guidelines as not strict enough.

The act allows warrantless use of the devices pursuant to the Foreign Intelligence Service Act, or in emergencies that involve imminent threat of death or serious injury, “conspiratorial activities threatening the national security interest” or “conspiratorial activities characteristic of organized crime” when there’s grounds for a warrant but insufficient time to get one.

Mark Jaycox, a legislative analyst for the Electronic Frontier Foundation, says the warrant exceptions should be tightened to ensure they are not abused.

Under the bill as drafted, he says, “you potentially have a very low bar for emergency use” – a concern even though the bill does require warrants be sought within 48 hours of emergency use and that data be purged if a warrant is not approved.

The StingRay II, manufactured by Harris Corporation, is used for surveillance purposes.

U.S. Patent and Trademark Office/AP

Jaycox says he’s also concerned that the bill grants an exception for Stingray use under the Foreign Intelligence Surveillance Act.

“This is a bill that’s implicated in a lot of the mass spying and bulk collection being done,” he says, “so that is a cause for concern because we simply don’t know how that will play out. A lot of that is classified.”

Chaffetz was unavailable to discuss the bill Tuesday, but Welch brushed off concern about FISA, saying the exception merely incorporates existing law.

“This legislation would require that if a Stingray is being used to get personal information you need to get a warrant,” Welch says. “There’s a recognition in our legislation that there could be exigent circumstances in great public safety threats and all uses of this Stingray are not the same.”

Judges and juries, Welch says, would decide the appropriate penalties for violators depending on individual circumstances.

State and local police departments often acquire the pricey devices using federal grants and the FBI appears to routinely require them to sign nondisclosure agreements, historically resulting in courtroom exchanges where police officers refuse to supply information to judges.

Last year, Maryland prosecutors withdrew tracking evidence after a judge threatened to hold a police officer in contempt for refusing to explain the Stingray-derived information, citing a nondisclosure agreement with the FBI. In Sarasota, Florida, the U.S. Marshals Service snatched Stingray records from local police in June after the department agreed to show them to the American Civil Liberties Union.

ACLU attorney Nathan Freed Wessler, a prominent advocate of privacy protections against Stingray use, told U.S. News in September the Justice Department likely could foist a warrant requirement on many state and local law enforcement agencies by requiring warrant-seeking agreements before providing funds or by withholding an apparently required FBI-signoff on sales without such agreement.

A law requiring warrants would be preferable, Jaycox says, because the Justice Department often interprets privacy rights in a manner detested by policy advocates, including opposing an ongoing fight in federal courts for a warrant requirement for historical cellphone location data.

ACLU legislative counsel Neema Singh Guliani says the influential advocacy group wants to be sure legislation is passed restraining the use not only of Stingrays, but also future technologies, and that loopholes be tightened.