Internet seems to call it "cease and desist lawyer".

(In short an 'Abmahnanwalt' is a lawyer who admonishes you for breaking certain rules and who can charge you for the service... quite close to 'Abschaum' in German dictionaries, as the basic idea may not really that bad, but it is heavily misused by some)

Source: https://www.dpreview.com/forums/thread/4060159