The problem, however, is that Justice Department policy is not law. And although the policy includes state and local law enforcement agencies when they are working on a case with federal agents and want to use the devices, it does not cover those agencies when they are working on cases alone. To address this loophole, lawmakers would need to pass a federal law banning the use of stingrays without a warrant, but efforts to do so have so far been unsuccessful.

One bigger issue with the Justice Department policy is that, as noted above, it only applies to criminal investigations, not national security ones, and it also includes a carve-out for “exigent circumstances” that are not clearly defined. Federal agents are not required to seek a warrant to use the technology in cases involving such circumstances. Whether the government has used the technology against Black Lives Matter protesters without a warrant is likely something that will remain a secret for some time.”