If you’ve ever filed a public records request with your local police department to learn more about how cell-site simulators are used in your community—chances are good that the FBI knows about it. And the FBI will attempt to “prevent disclosure” of such information.

Not only can these devices, commonly known as "stingrays," be used to determine a phone’s location, but they can also intercept calls and text messages. During the act of locating a phone, stingrays also sweep up information about nearby phones. Last fall, Ars reported on how a handful of cities across America are currently upgrading to new hardware that can target 4G LTE phones.

The newest revelation about the FBI comes from a June 2012 letter written by the law enforcement agency to the Minnesota Bureau of Criminal Apprehension. It was first acquired and published by the Minneapolis Star Tribune in December 2014—similar language likely exists between the FBI and other local authorities that use stingrays.

As the letter states:

In the event that the Minnesota Bureau of Criminal Apprehension receives a request pursuant to the Freedom of Information Act (5 USC 552) or an equivalent state or local law, the civil or criminal discovery process, or other judicial, legislative, or administrative process, to disclose information concerning the Harris Corporation [REDACTED] the Minnesota Bureau of Criminal Apprehension will immediately notify the FBI of any such request telephonically and in writing in order to allow sufficient time for the FBI to seek to prevent disclosure through appropriate channels.

While the FBI did not immediately respond to Ars’ request for comment, privacy activists were dismayed to see this language.

“It’s remarkable to see collusion by state and federal agencies to undermine public records requests, which are clearly aimed at keeping the public in the dark about the use of Stingray technology,” Hanni Fakhoury, a lawyer with the Electronic Frontier Foundation, told Ars. “After all, any truly sensitive law enforcement details could be redacted under traditional public records act law. But the notion that the federal government would work to actively block disclosure of records seems clearly to have a chilling effect on obtaining information about this controversial surveillance tool.”

Staying mum

Earlier this month, Mike Katz-Lacabe , a California-based privacy activist, submitted public records requests to the 100 largest local law enforcement agencies in the country. So far, he has only received one response— notification by the police in Tacoma, Washington, to the FBI concerning a records request made by an Associated Press reporter in October 2013.

“I am trying to systematically determine which law enforcement agencies have these cellular telephone surveillance and monitoring devices,” he told Ars by e-mail. “My first set of requests was sent to the law enforcement agencies of the 100 largest cities in the US. My next requests will go to the state police departments (or public safety departments) of all 50 states and to the county police/sheriff departments.

“The secrecy around these devices (Stingray, KingFish, DRTbox) suggests that it is critical to national security. However, these devices are mostly used in regular criminal cases as a standard tool of local police departments and as such, should be subject to the same disclosure as any law enforcement tool.”

Worst-kept secret

Relatively little is known about how, exactly, the stingrays are used by law enforcement agencies nationwide, although documents have surfaced showing how they have been purchased and used in some limited instances. In 2013, Ars reported on leaked documents showing the existence of a body-worn stingray. Back in 2010, Kristin Paget famously demonstrated a homemade device built for just $1,500.

Worse still, cops have lied to courts about the use of such technology. Just last month, two US senators made public the FBI’s position that the agency could use stingrays in public places without a warrant. The largest manufacturer of the devices, the Harris Corporation, has routinely been tight-lipped about its hardware capabilities.

Many legal experts have pointed out that a federal agency like the FBI should not have any bearing on whether a state agency complies with state law.

“It is surprising in the sense that it seems like just a completely inappropriate and over-broad use of federal authority,” Nathan Wessler, an American Civil Liberties Union attorney, told Ars. “What is most egregious about this is that, in order for local police to use and purchase stingrays, they have to get approval from the FBI, then the FBI knows that dozens of police departments are using them around the country. And yet when members of the press or the public seek basic information about how people in local communities are being surveilled, the FBI invokes these very serious national security concerns to try to keep that information private.”

Others, though, pointed out that the FBI is likely not doing anything illegal by compelling police departments to hand over public records requests. After all, public records in and of themselves are by definition, public.

“The fact that you get put on a notification, might maybe, sometimes, help [the FBI] catch some bad players,” Daniel Stotter, an Oregon-based public records lawyer told Ars. “It doesn't mean you're going to get picked on or arrested. I would not be scared to make a request. It wouldn't scare me, but would it scare Grandma? Maybe. Would it [put a chilling effect] on some people? Sure. But if you’re going to investigate law enforcement then you've got to be a tough cookie.”