The high court will hear the case Wednesday that could plunge the earliest images of Disney's mascot and other closely held creative property into the public domain as early as next year.
If upheld, the precedent-setting challenge could cost movie studios and heirs of authors and composers millions of dollars in revenue as previously protected material becomes available free of charge.
At issue is a 1998 law that extended copyright protection an additional 20 years for cultural works, thereby protecting movies, plays, books and music for a total of 70 years after the author's death or for 95 years from publication for works created by or for corporations.
The law was almost immediately challenged by Stanford University law professor Lawrence Lessig on behalf of Eric Eldred, who had been posting work by Nathaniel Hawthorne, Henry James and others on his Web site.
The plaintiffs lost their case at trial and then on appeal but stunned many observers by persuading the Supreme Court to hear the case.
"Nobody has ever attacked the extension of copyright before," said Lionel Sobel, editor of the Entertainment Law Review. He said the Internet has pumped up the demand for images that are now protected.
"Now we have thousands of people who want to create a Web site and would like to have ready access to a whole library of materials," Sobel said.
The Copyright Term Extension Act of 1998 was sponsored by late Rep. Sonny Bono and quickly became known as the "Mickey Mouse Extension Act" because of aggressive lobbying by Disney, whose earliest representations of its squeaky-voiced mascot were set to pass into the public domain in 2003.
The impact of the law extends far beyond corporations. Small music publishers, orchestras and even church choirs that can't afford to pay high royalties to perform some pieces said they suffer by having to wait an additional 20 years for copyrights to expire.
Compositions such as Gershwin's "Rhapsody in Blue," which would have passed into the public domain in 1998, now are protected until 2018 at least. Books by Ernest Hemingway and F. Scott Fitzgerald also were due to become public property.
Lessig claims Congress acted unconstitutionally by extending copyright protection 11 times over the past 40 years. The plaintiffs contend the Constitution grants Congress the right to grant copyright protection for a limited time and that the Founding Fathers intended for copyrights to expire so works could enter the public domain and spark new creative efforts to update them.
The plaintiffs also claim that by extending copyright protection retroactively, Congress has in effect made copyright perpetual largely in response to corporate pressure.
The government and groups representing movie studios and record labels argue that the Constitution gives Congress, not the courts, the job of balancing the needs of copyright holders and the public, especially in the face of new technology.
Backers of the extension also argue that the Internet and digital reproduction of movies and music threaten the economic viability of creating those works, thus requiring greater protection.
"This is essentially a dispute about policy dressed up as a Constitutional question," The Walt Disney Co. said in a statement. "Eldred is simply trying to second-guess what Congress has already decided, and we believe the Supreme Court should reject their attempt."
Disney has come under special criticism because the company reaped a fortune making films from such public domain fairy tale characters as "Snow White" and "Cinderella," but is fighting to prevent others from doing the same with characters like Mickey Mouse and Donald Duck.
Legal experts said it would be unlikely that Disney and other companies would suffer immediate harm if copyrights expire on their movies and characters.
Mickey Mouse, for instance, is not only a character but a corporate trademark, which never expire as long as they are in use.
Only the copyright on the Mickey portrayed in Disney's earliest films, such as 1928's "Steamboat Willie," would expire in the next few years. The more rounded, modern mouse familiar today is a later creation and would remain protected for several more years.