Once a work has entered the public domain, the original owner no longer has rights over it.  This clause of copyright law has proven challenging as past copyright holders have attempted to reclaim their rights when it becomes suddenly convenient.  This is the subject of the U.S. Supreme Court case Dastar Corp. v. Twentieth Century Fox Film Corp.

In 1948, Fox obtained rights to create a television series called Crusade in Europe based on a book written by Eisenhower and published by Doubleday.  Doubleday renewed the copyright to the book in 1975; however, Fox chose not to renew their copyright on the series, which thus entered public domain in 1977.  Dastar then took the series in 1995, edited and manipulated them, and repackaged them.  They sold the new videos and credited Dastar employees as producers and not the original book or TV series.

Fox sued in 1998, attesting that Dastar had infringed on copyright and had "passed off" the work as their own.  The district court found for Fox and awarded it double Dalstar's profits.  Finally, the U.S. Supreme Court reversed the decision of the district court and another appeals court.  In an 8-0 ruling, the court reasoned that once a work passes into the public domain, anyone in the public may do anything he or she wishes with it and does not have to attribute the author.

This court ruling helps promote creativity somewhat by assuring artists that anything in the public domain is fair game for their use in future works.  However, there is still the fear that someone might try to claim rights, and often the potential battle isn't worth it.  In addition, copyrights today, thanks to extensions, are so long that producers and publishers don't need to renew copyrights because they last well over the death of the author.  Once again, the copyright monster scares small companies from creating for fear of infringement.