Fanfiction has encountered problems with intellectual property law due to usage of copyrighted characters without the original creator or copyright owner's consent. See more

Significant amounts of copyrightable creative works such as motion pictures, television programs, music, and computer gaming works are produced in the United States. … See more

Separate from the legal issues raised by fanfiction's interaction with copyright law, legal issues may also develop from United States trademark law.
Current federal trademark law follows the Lanham Act, otherwise known as the Trademark Act of … See more

Many countries, and some U.S. states, have laws governing rights of publicity. In the United States, rights of publicity are governed by state statutes and state common law, and thus vary from state to state. As a general matter, the right of publicity grants a … See more

In 2007 two UC Davis Law School professors argued in the California Law Review that "Mary Sue" fan fiction "that challenge the orthodoxy of the original likely constitute fair use". Citing Campbell v. Acuff-Rose Music, Inc.—which established that … See more

Some copyright holders have stated specific positive or negative attitudes towards fanfiction.
Examples
Studios, productions companies, and producers
Most major studios … See more

In Great Britain, Discworld author Terry Pratchett, up until the point of his death in 2015, emphasized that he was careful not to read fanfics, and had voiced the opinion that "everything works if people are sensible" and didn't mind "so long as people don't put it … See more