Like a bad grade in college that you don’t think you deserve, a Motion Picture Association of America movie rating is something you can sometimes appeal. There are many instances of Hollywood films being slapped with ratings that their producers and studios abhor. After all, filmmakers want the biggest audience possible for their movies. There are a few celebrated cases of movies doing well despite “extreme” ratings-Last Tango in Paris and its X comes to mind-but for most filmmakers, anything stronger than an R is too risky. The appeals process is somewhat opaque and involves meeting with an appellate board and presenting the case. Victories are rare, but Harvey Weinstein just claimed a big one for Blue Valentine, the Oscar hopeful starring Michelle Williams and Ryan Gosling.
https://www.newsweek.com/2010/12/09/seven-biggest-movie-ratings-fights.html