Film censorship is as old as films themselves. As with any form of mass entertainment, concern has always been expressed by elite powers about the effect of these texts on an uneducated and unrestrained populace, and measures have been taken to protect the people against themselves. This was not so much of a problem when films deal with trains pulling into stations and men knocking down walls, but, as films acquired more complex narratives and competed for audiences in a more crowded market, censorship and classification systems were developed to control who saw what.
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General Principles of The Hays Code,
governing motion picture production in the US from 1930 till 1960
Attitudes towards what is acceptable on a large screen varied as much from country to country now as they do then. Europe has always been more accepting of nudity and sexual content than America, which has strict limits on, for instance, the showing of nipples. However, much of what is considered acceptable content in America in terms of violence, is snipped out by European censors, especially in Britain. However, US censors often baulk at the depiction of sexual acts, especially if they involve non-heterosexual sex, or non-missionary positions.
After concerns voiced by Church and State the Association of Motion Picture Producers and The Motion Picture Producers and Distributors of America adopted the Hays Code in 1930. It placed strict prohibitions on what could and could not be shown on screen. Based on deeply racist, sexist and elitist — and strongly Roman Catholic — principles, it sought to sanitise the movies. From its inception, the Production Code Administration was controlled by Catholic laymen, and worked hand-in-glove with the Catholic Legion of Decency to ensure that the morality enforced was based on Catholic teachings, particularly when it came to sexuality and reproduction.
Ironically, some of the films it most severely affected were adaptations of literary classics, such as Anna Karenina and The Grapes of Wrath. As well as prohibiting the depiction of miscegenation, marital sex, or the profit from crime, it placed curbs on a whole range of bodily functions. Hitchcock's Psycho (1960) is famous for many things, not least because it shows the first ever toilet in the act of flushing to appear on a cinema screen in the US.
The Moon is Blue, a 1953 film directed by Otto Preminger, is often credited with beginning the stampede away from the code. Breen objected to the screenplay, citing its objectional moral tone and careless use of words such as "virgin". Preminger ignored the requests for cuts, and released his film without a rating. Although this restricted the number of theatres it could play in, and meant it was banned in certain regions (e.g. Boston), the film was a box office success. Breen resigned as head of the Code administration the following year. Heartened by Preminger's example, producers and studios felt emboldened to ignore the Code, and by the early 1960s it had fallen out of use. It was replaced in 1966 by the MPAA's rating system.
The 2006 documentary, This Film is Not Yet Rated examined the anomalies within the MPAA and is vital viewing for anyone interested in the mechanics of film censorship in the USA.
Classification system - from hk.gov.org