Roughly eight years after information about law enforcement use of Stingray devices began slowly making its way into the public sphere, positive changes are being made. While the government has often argued it can be the "Third Party" in "Third Party Doctrine" by inserting itself warrantlessly between people's cell phones and their carriers' towers, its assertions are being met with increased judicial skepticism.
Two judges -- one state, one federal -- have reached the same conclusion in recent months: using a cell tower spoofer to locate suspects by dragging information out of their phones is a search under the Fourth Amendment. Warrants are required.
A few state legislatures have gotten into the act as well, proposing laws that create a warrant requirement for Stingray deployment. Illinois is the latest to do so (and the law actually passed), creating a new set of guidelines for law enforcement Stingray device use, including limits on data retention. It doesn't go quite so far as to mandate warrant acquisition, but it does force law enforcement to specify the equipment used in their applications, which also serves to create a paper trail that can be examined by defendants and members of the public.