According to Wikipedia: "The Motion Picture Production Code was the set of industry censorship guidelines which governed the production of the vast majority of United States motion pictures released by major studios from 1930 to 1968. It was originally popularly known as the Hays Code, after its creator, Will H. Hays.
The Motion Pictures Producers and Distributors Association (MPPDA), which later became the Motion Picture Association of America (MPAA), adopted the code in 1930, began effectively enforcing it in 1934, and abandoned it in 1968 in favor of the subsequent MPAA film rating system.
The Production Code spelled out what was acceptable and what was unacceptable content for motion pictures produced for a public audience in the United States."
While this code governed an industry, it ties in to the legal system in terms of how obscenity was defined and determined during the time that the code was enforced by Hollywood.