http://en.wikipedia.org/wiki/Mitchell_brothers
"In the mid-1970s, low-level organized crime began making unauthorized copies of the Mitchells' movies, and the brothers retaliated in the courts. When one judge ruled that obscene material could not receive copyright protection, the brothers eventually prevailed in the 5th Circuit Court of Appeals,[3] leading to the FBI copyright warnings now found at the start of videotapes.[4]"