The Department of Justice (DOJ) is going to pull back the curtain and conduct a formal review of how, when, and why it uses mobile phone surveillance devices, commonly known as stingrays, according to a report Sunday evening from The Wall Street Journal . However, the DOJ has yet to determine exactly when and how this will occur.

Devlin Barrett, the WSJ reporter who broke the story, tweeted that the internal review began before recent Attorney General Eric Holder left office. According to the story, an unnamed DOJ spokesman said that the agency is "examining its policies to ensure they reflect the Department’s continuing commitment to conducting its vital missions while according appropriate respect for privacy and civil liberties."

UPDATE Monday 10:19am CT: Patrick Rodenbush, a spokesman with the DOJ, e-mailed Ars the exact same statement.

Not only can stingrays, or cell-site simulators, be used to determine location by spoofing a cell tower, they can also be used to intercept calls and text messages. Once deployed, the devices intercept data from a target phone as well as information from other innocent phones within the vicinity. For years, federal and local law enforcement have tried to keep their existence a secret while simultaneously upgrading their capabilities.

Less than a week ago in fact, a robbery suspect in St. Louis who had previously pleaded guilty changed her plea after discovering that a stingray was used in her case. The prosecutors next dropped the charges—and the attorneys continue to insist this change of heart had nothing to do with the snooping technology.

Typically, police deploy stingrays without first obtaining a search warrant. In January 2015, the FBI asserted that it does not need a warrant to use them in public. So if law enforcement seeks judicial approval at all, it’s usually under a "pen register and trap and trace" application. This requires the authorities to show relevance to a criminal investigation rather than prove the probable cause necessary for a warrant. Judges who sign off on these arrangements have been typically unaware of the stingrays' full capabilities.

The veil of secrecy surrounding these devices has lifted ever so slightly over the last year. Similar to the St. Louis incident, there has been a small handful of known criminal cases nationwide where charges have been impacted or dropped because the defendants challenged the use of stingrays. Cops have even lied to courts about their use. These results stem from the FBI's non-disclosure agreement with various law enforcement agencies nationwide, and the agreements have only recently been published in full and unredacted form.

Civil liberties advocates lauded the DOJ's move and looked forward to more details being revealed. American Civil Liberties Union Attorney Nathan Wessler told Ars a shift toward transparency and using warrants is "long overdue," but the slow pace of that transition is troubling. "[It's] disturbing that the FBI has been gagging local police from telling judges and defense attorneys about stingray use, yet doing nothing to ensure that local law enforcement uses this technology in accord with the Fourth Amendment."

Former public defender and current Electronic Frontier Foundation Staff Attorney Hanni Fakhoury also applauded the move, noting that all the secrecy hurt public safety in concrete ways through the dismissed cases. "The fact the federal government wasn't providing any real oversight or guidance on how to use these devices, coupled with the non-disclosure agreement, meant local departments were out figuring it out on their own," he told Ars via e-mail. "You've seen the backlash as local communities learn about the existence of these devices. I just hope there's more than an internal conversation and investigation but meaningful change, including the use of a warrant nationwide before deploying these devices, as well as significantly improved transparency and accountability."

New York Civil Liberties Union Attorney Mariko Hirose led the charge recently to force the Erie County Sheriff's Department to disclose stingray documents. She hopes the DOJ's move to revisit their stance on stingrays and warrants can trickle down to those local law enforcement agencies also currently deploying stingrays.

"Although we still have a lot to learn about what and when DOJ will reveal and what the result of the review will be, local law enforcement should pay attention to this shift and take note that the FBI has been getting warrants in recent months before using stingrays," she told Ars by e-mail. "The Erie County Sheriff's Office's policy on use of stingrays, by contrast, does not require obtaining warrants. This is a powerful surveillance device, and law enforcement should at minimum be obtaining a warrant before using it."

Neither the FBI, the DOJ, nor the Harris Corporation, the dominant manufacturer of such devices, immediately responded to Ars’ request for comment.