EFF sued the DOJ and FBI to shine light on the U.S. Marshal Service’s (USMS) use of small aircraft mounted with controversial cell-phone tracking systems.

The Wall Street Journal revealed last year that the Marshals have been flying small, fixed-wing Cessna planes mounted with IMSI catchers—devices that emulate cell phone towers and are able to capture the locational data of tens of thousands of cell phones during a single flight. The planes—in the air since 2007—reportedly were based out of five metropolitan airports and shared by multiple agencies within the U.S. Department of Justice, even as sources within the agency questioned the legality of the program.

In the press, IMSI catchers are also known as “stingrays,” a name taken from the “Stingray II” device manufactured by Harris Corporation, or “dirtboxes,” a nickname for Boeing subsidiary Digital Receiver Technology’s “DRT” devices. Across the country, the Justice Department has intervened in local public records battles to prevent the release of information about these technologies, employing tactics such as signing nondisclosure agreements with state and local law enforcement agencies, seizing records held by those agencies, and withholding key pieces of information about the technology from judges and criminal defendants.

A week after the Wall Street Journal story kicked off a media firestorm, EFF filed a comprehensive FOIA request with Justice Department and FBI over the USMS program, seeking a wide variety of records, including policies, procedures, training materials, communications about the legality of the program, and documentation of each use of the spy planes.