The Justice Department is reining in federal agents’ use of cell-site simulators that collect in bulk information on cellphone users in a specific geographic area, but privacy advocates aren't satisfied with initial steps toward shielding location data of innocent Americans from warrantless collection.

Federal and local officials' use of the devices, the best-known being Stingrays made by Harris Corp., is cloaked in secrecy, but appears often done without warrants and at times is concealed from courts, with police citing nondisclosure agreements they signed with the FBI.

Now, the Justice Department announced Thursday, its employees and agents working under its umbrella in agencies such as the FBI, the U.S. Marshals Service and Drug Enforcement Agency, must generally get a warrant to use cell-site simulators.

But the policy, which retains loopholes for exigent circumstances such as "hot pursuit of a fleeing felon" or to spare someone from death or serious injury and for "very limited" exceptional circumstances, isn’t as far-reaching as privacy advocates would like, and it doesn’t affect local law enforcement agencies when they are not working with federal authorities.

Among the policy changes, federal agents must henceforth be trained in how to use the machinery, and data stored on the devices must be purged within 30 days or immediately if a target device is located.

A policy document outlining the pivot says in a footnote the guidelines are "intended only to improve the internal management of the Department of Justice" and do not "create any right of review in an administrative, judicial, or any other proceeding."

The document addresses the relevance to local and state law enforcement briefly, saying only that it applies to "instances in which Department components use cell-site simulators in support of other Federal agencies and/or State and Local law enforcement agencies."

The document was produced months after the FBI clarified that non-disclosure agreements it has required local law enforcement to sign should not be read as allowing them to evade courtroom disclosures.

American Civil Liberties Union attorney Nathan Freed Wessler, one of the most prominent advocates of privacy protections against Stingray use, says the effect of the new policy on state and local authorities appears limited.

“Disturbingly," he said in a statement, "the policy does not apply to other federal agencies or the many state and local police departments that have received federal funds to purchase these devices."

Justice Department spokesman Patrick Rodenbush confirms the rules do no constrain law enforcement when they are not working with the department's authorities.

Wessler tells U.S. News the Justice Department could with two steps, however, foist the warrant requirement upon most local law enforcement agencies.

First, he says, many of the pricey devices are purchased using grants from the Justice Department or the Department of Homeland Security. The Justice Department could require its grant recipients to get a warrant, he says.

Perhaps more significantly, Wessler says, the FBI must sign off on all sales of the cell-site simulators sold by Harris Corp. and its competitors, meaning the bureau could require warrants, much as it requires non-disclosure contracts.

In addition to a universally applied warrant requirement, Wessler wants the department to close the policy loopholes and for Congress to pass legislation that would ensure privacy protections.

Local police use of Stingrays has stoked rage recently.

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

A legal effort to win warrant protection for historical cellphone location data, meanwhile, appears headed to the Supreme Court, which conceivably could result in mandatory warrants for federal and local use of Stingray devices.

The related effort includes two cases in which historical cellphone location data was taken by authorities from service providers as part of Miami and Baltimore robbery investigations.

An Atlanta-based federal appeals panel ruled a warrant should have been required to collect that information, which is similar to what Stingrays collect, but an en banc review by the U.S. Court of Appeals for the 11th Circuit in May overturned the ruling. In August, a panel of the 4th Circuit, however, ruled warrants are constitutionally necessary for historical location data, enhancing the likelihood the Supreme Court will accept the matter.

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The Supreme Court recently required warrants for GPS tracking of vehicles and extended warrant protection to the cellphones of people who are arrested, giving advocates hope for a privacy-enhancing outcome.