That requires a warrant. Surprised the FCC allows them to tamper with peoples phones tbh. Its all sketchy as heck and flawed if cases are dismissed when they question how the tech works.
Last I heard the FCC doesn't. When people complained the devices were not licensed the FCC issued licenses "for emergency use only". That's probably because interference with radio communications is against the law and the FCC as a mere regulator is subject to that law.
All rather moot as these things are mostly used for various forms of illegal surveillance. The police have to keep their activity as secret as possible. That includes the fact that they are using them in the first place.
This whole issue isn't new. The police normally do, or get others to do, surveillance that is illegal in various ways. The existence of these sorts of devices is an expression of a kind of desperation. Privacy is getting too good. So this might actually be a good thing if this forces a long overdue discussion.
They're probably using it for parallel construction rather than gathering actual evidence for a court case. In other words, it will help them understand how/where to look for evidence that will be admissible in court.