Someone is described as, or actually named, the <Something> Police.
Rolling Updates, No Launching Please, Needs More Examples. Much like the term "Nazi", the term "Police" is often attached to a person or group to describe them as overly zealous toward that particular subject. A Grammar Nazi may be asked, "What are you, the Language Police?!" This only includes non-standard uses of the term, so the Detroit Police would not be an example of the trope, but the Fashion Police would (which, BTW, needs to be a trope of its own). It can also include fictional groups whose names fit the pattern, and are clearly not really law enforcement officials. In no way related to The Police. (Could possibly be expanded to include "(The) X Nazis", as supertrope to Grammar Nazi, if you like).
ExamplesAnime and Manga