Prior to 1976, courts had been applying a fair use exception based on common law rather than statute. (law.stackexchange.com)
If so, the sexual activity is not lawful and the private use exception does not apply. (lawnow.org)
When someone finds a new way to violate a copyright it is almost impossible to know whether this falls under the fair use exception until it goes to court. (indiesunlimited.com)