It's a Wonderful Life aired on television last weekend—one of its only 1999 broadcasts. Just a few years ago, the movie seemed to be shown on a different channel almost every day throughout the Christmas season. What changed?
U.S. copyright law determines who may distribute, display, or reproduce a film, a book, a drawing—essentially anything "fixed in a permanent medium," as the lawyers like to say. Works not covered by copyrights--including ones with copyrights that have expired and those that never secured this protection—are said to be in the "public domain." These works, like the near-ancient Sherlock Holmes stories and some of Charlie Chaplin's silent films, can be reproduced, broadcast, and sold freely.
It's a Wonderful Life entered the public domain by accident. In 1946, when the movie was filmed, U.S. copyright protection lasted 28 years and could be renewed for another 28 years by filing some paperwork and paying a nominal fee. However, Republic Pictures, the original copyright owner and producer of Wonderful Life, neglected to renew the 1946 copyright in 1974. So, the film entered the public domain. Though a box office flop on release, it became immensely popular on television thanks to repeated showings: Stations programmed it heavily during the holidays, paying no royalties to its producers, and more than 100 distributors sold the movie on tape.
Republic regained control of the lucrative property in 1993 by flexing a new Supreme Court ruling that determined that the holder of a copyright to a story from which a movie was made had certain property rights over the movie itself. Since Republic still owned the copyrighted story behind It's a Wonderful Life and had also purchased exclusive rights to the movie's copyrighted music, it was able to essentially yank the movie out of the public domain: It claimed that since Wonderful Life relied on these copyrighted works, the film could no longer be shown without the studio's blessing. (Technically, the film itself is not copyrighted. One could hypothetically replace the music, rearrange the footage, and sell or show the new product--but no one has done this.) In 1994, Republic * signed a "long-term" deal granting NBC exclusive rights to broadcast the movie, and the network typically does so between one and three times a year.
Wonderful Life won't re-enter the public domain for quite a while. Congress has repeatedly expanded copyright protections and made them effective retroactively. Most recently, at the behest of Disney and other large media corporations with soon-to-expire copyrights, Congress added 20 years to all existing copyright claims. They now stand at 95 years for copyrights held by corporations. (The copyright protection for individual writers and artists lasts 70 years beyond their deaths.) Thus, showings of Wonderful Life will remain limited well into the 21st century.
* In 1998 Republic's parent company, Spelling Entertainment (a subsidiary of Viacom), sold the rights to Republic's film library to Artisan Entertainment.