There have been a handful of prosecutions (and many hundreds of firings) for misuse of the FBI's NCIC database by law enforcement officials. For instance, ex-NYPD Sergeant Joseph Dwyer was convicted of conspiracy in federal court in 2016 for selling information from NCIC to private defense investigators.
Personally, I believe this kind of breach-of-trust should be prosecuted much more vigorously. But besides the fear of embarrassment, I suspect federal agencies are unwilling to
compromise intelligence methods to prosecute misbehavior.
The key here is Misuse under the FBI's guidelines which are no where near as strict as they should be under a properly enforced 4th amendment, most of what the FBI collects in the first place should be unconstitutional for them to have if we had a properly enforced constitution, unfortunately we do not.