A lawyer for the Web magazine 2600 urged a federal appeals court to find unconstitutional a law that seeks to limit the unauthorized copying of digitized material.

A lawyer for the Web magazine 2600 urged a federal appeals court in Manhattan yesterday to find unconstitutional a 1998 law that seeks to limit the unauthorized copying of digitized material.

The closely watched case, which pits a hacker Web site against eight leading movie studios, is the first major challenge to the Digital Millennium Copyright Act. The law is aimed at updating copyright law for an age when copying music, movies and books in digital form is much easier and less expensive than ever. The provision at issue specifically prohibits the dissemination of devices capable of breaking the technological wrappers intended to prevent the copying of digital material.

A three-judge panel of the United States Court of Appeals for the Second Circuit is weighing whether to overturn a lower court ruling that prohibits the site, www.2600.com, from publishing or linking to DeCSS, a computer program that can crack the security system on DVD movies. Once the disc with the movie has been unlocked, an individual can copy it to a computer hard drive and use another program to shrink it into a format that can be distributed over the Internet.

The movie studios sued Eric Corley, the publisher of 2600, in January 2000 after he posted DeCSS on his Web site and linked to other sites distributing the program. At the time, Mr. Corley said he wanted to make the program available to users of the Linux operating system, who could not play store-bought DVD's on their computers without first breaking their digital lock. (The DVD's work on the Windows operating system, but not on Linux.) The lower court issued an injunction against Mr. Corley's site in August.

At the core of the case is the question of whether the Digital Millennium Copyright Act violates the First Amendment by blocking even the limited uses of copyrighted material now permitted for purposes like scholarship, criticism or parody.

Yesterday, Kathleen Sullivan, the dean of Stanford Law School who is representing Mr. Corley, compared the lower court's injunction to prohibiting the publication of blueprints to build a copying machine. Although a copying machine could be used for copyright infringement, it also has many other legitimate uses, Ms. Sullivan argued.

And some of those purposes come under the "fair use" doctrine, which has historically balanced the free- speech rights of users with the rights of copyright holders, she said.

But Judge Jon O. Newman, an expert on copyright issues, responded that fair use was not necessarily guaranteed in the manner Ms. Sullivan suggested. As long as critics could quote from a given work in a newspaper or copy a clip of a movie from another medium, like videotape, their First Amendment rights remained protected, he suggested.

"Have we ever said that you not only get to make fair use, but you get to make it in the most technologically modern way?" Judge Newman asked.

Ms. Sullivan countered that denying users the most technologically advanced means to make fair-use copies would be like leaving them behind in "the horse-and-buggy era" while copyright holders "advance into the 21st century."

Charles Sims of the New York law firm of Proskauer Rose, who argued for the studios, said that the law was necessary to prevent the "Napsterization of the movie industry," referring to the music industry's dispute with Napster, the popular music- swapping service. Without the 1998 copyright act, he said, Hollywood would have little motivation to distribute its movies in digital form.

And Daniel Alter, an assistant United States attorney who argued for the government, said the court need not even address the issue of fair use, because Mr. Corley's case was simply about the distribution of a decryption device.

The panel asked several questions of Mr. Alter about the rationale for preventing Mr. Corley from linking to other sites that distributed DeCSS, including whether an online newspaper under the same logic would be liable for a link to contraband or other illegal material.

"They would have to be interested in facilitating the distribution of contraband," Mr. Alter said, adding that he believed that Mr. Corley was intentionally trying to disseminate the code with the links on his site.

The judges seemed less interested in another prong of Ms. Sullivan's argument, which contends that computer code like DeCSS should be entitled to the highest degree of First Amendment protection because it is a means of expressing ideas. In his initial ruling on the case, Federal District Court Judge Lewis Kaplan noted that not all speech was protected by the First Amendment, particularly when it is being used for illegal conduct, as in burning a draft card.