Just how long will Disney Corp. retain its exclusive rights to the world-famous Mickey Mouse?

This week, a team of Harvard legal experts filed a court challenge to a law that postpones the expiration of copyrights on intellectual property. The challenge was filed by Berkman Professor of Law Lawrence Lessig; Weld Professor of Law Charles R. Nesson '60; Jonathan L. Zittrain, executive director of the Law School's Berkman Center for Internet & Society; and Geoffrey S. Stewart of the Boston law firm Hale and Dorr.

The Sonny Bono Copyright Term Extension Act (CTEA), signed into law by President Clinton last year, retroactively extends copyright protections for artistic creations ranging from cartoon characters to literary classics.

Under old laws, books published as late as 1923 were scheduled to enter the public domain this Jan. 1. CTEA prolongs the duration of their copyrights to Jan. 1, 2019.

Nesson characterized the case as a clash of "logic and power," and his colleague Lessig noted that it is the first legal challenge of its kind.

While he stressed that Congress has passed retroactive copyright extensions before, Lessig said CTEA is the first to be contested.

"We think we've got an awfully good position," Nesson said. "We think the statute is very vulnerable."

The Harvard legal squad took the case on behalf of Eldritch Press, a non-profit purveyor of literary works over the Internet.

The law professors are joined by Stewart, whom Lessig called a "litigation specialist."

According to Zittrain, the expiration of copyrights allows Eldritch to reproduce books online and make them available to Internet users free of charge.

"If our suit is not successful," Zittrain said, "Eldritch will run out of materials to post, or they will have to post texts published since 1923 and riskcriminal charges."

Originally proposed by the late Rep. Sonny Bono(R-Calif.), CTEA was sponsored in the Congress byRep. Mary Bono, who won her husband's seat afterhis death in 1997. President Clinton signed thebill into law after its passage in 1998.

Responding to news of the court challenge,Frank W. Cullen Jr., Bono's press secretary,explained the intent of the bill.

"Any time that someone tries to deprive artiststhe right to benefit from their work, that issomething we're concerned with," Cullen said.

Lessig pointed out that the Disney Corp. haslong supported legislation to prolong copyrightprotections.

"Extension of copyright acts seem closelyrelated to preventing Mickey Mouse from cominginto the public domain," Lessig said.