It's probably referring to acts carried out by youngsters in the banlieus (low income areas of France's big cities). Stuff like ambushing police and fire brigades for lolz, partaking in protests they care nothing about to just loot and burn, low/mid scale drug dealing etc.
Police has real problems dealing with these types cause there are so many of them together and they quickly scurry back in to their impenetrable tower blocks.
Or am I oversimplifying. Please say so.