NEW YORK -- At the University of North Carolina's libraries, scholars can view thousands of books and academic journals over the Internet.
But legal or technical restrictions prevent them from printing or e-mailing pages to colleagues, the way they can legally photocopy items in print for scholarly discussions.
And interlibrary loan is often barred, meaning professors can't request an obscure journal from another library in digital form.
While the Internet is making more information available at one's fingertips, efforts to curb copyright infringements are also curbing that flow of knowledge. Critics say these are overweening safeguards that block the so-called "fair use" of copyrighted material permitted under U.S. law.
Larry Alford, the deputy university librarian, worries about how researchers at multiple locations can continue to collaborate. He's no fan of digital barriers.
"Over time it will do great harm," Alford said. "Much of the research and discovery is done through collaboration."
Laura Gasaway, a University of North Carolina law professor who also runs the school's law library, said a copyright clause was written into the U.S. Constitution "not just to reward authors or creators but to make these works available to the public."
Content producers insist that such controls are necessary for them to feel comfortable about distributing digital materials in the first place. They want to avoid another case of Napster, the service where millions of Internet users traded copyrighted music.
Consider digital video disks, or DVDs. Fritz Attaway, executive vice president of the Motion Picture Association of America, said movie studios refused to release films in DVD format without an encryption mechanism to prevent copying.
Soon after DVDs came out, though, a Norwegian hacker broke the coding scheme. Hollywood went to court to stop a hacking magazine, 2600, from posting links to the descrambling software.
Movie studios won an injunction under the 1998 Digital Millennium Copyright Act, a law that bars attempts to circumvent technology designed to protect copyrighted works. The case is under appeal.
In a separate lawsuit, a Princeton University professor wants to strike down the 1998 law on grounds that it hinders academic freedom.
That professor, Edward Felten, responded to the music industry's challenge to break a copy control scheme. Felten and his colleagues said they succeeded, but the music industry tried to stop them from discussing results at a spring conference.
Both cases cited "fair use", the provision in copyright law that makes it legal to copy books, music and other materials for criticism, commentary, news reporting, teaching and research.
It's the same provision that allows professors to photocopy a printed journal article for colleagues at another university. It's also the basis for parodies of pop songs and home taping of television shows.
The 1998 law preserves fair use, but permits access controls. So researchers may have the legal right to excerpt a book once they obtain it, but obtaining it in the first place may be illegal.
Here lies the problem: Making access available for fair use also makes it available also for unfair uses such as piracy.
The problem isn't unique to the digital world, but the potential losses from unauthorized uses are more pronounced. In the past, copies weren't as good as the original. Now they are.
Because there's greater harm to the potential market with digital copies, what is fair in print may not be so in electronic form, said Allan Adler, a vice president of the Association of American Publishers.
"Fair use is important. We respect it," Adler said. "But I would argue it may apply differently."
The movie industry's Attaway believes that fair use narrows in the digital age, just as it expanded when the Supreme Court ruled in 1984 that video cassette recorders are permissible for "time shifting" programs.
"As technology permits copyright owners to maintain better control, the definition of fair use may contract," he said.
Napster lawyers tried arguing that its music service was permitted under fair use, citing the ruling on time shifting. In this case, some Napster users were "space shifting" music - using the Internet to access songs they already owned on compact discs.
The courts rejected that and other fair use arguments, noting that the songs also became available to millions of others and deprived copyright holders of potential revenue.
Jane Ginsburg, a Columbia University law professor, said fair use was never meant to be a blank check for personal copying. Rather, she said, it was designed to encourage scholars to expand on existing works, through commentary and other research.
It's unclear, she said, whether digital controls truly compromise the ability to extend existing works.
Brad Smith, deputy general counsel at Microsoft Corp., notes that despite copy restrictions on its Encarta encyclopedia package, schoolchildren still include snippets in book reports. Copyright holders, he said, will always keep consumers in mind.
"The rise of online content doesn't mean the death of common sense," he said.
The U.S. Copyright Office failed to find any actual or likely harm to fair use during a recent review of the 1998 access controls.
Marybeth Peters, the U.S. register of copyrights, said many of the digital works in question still exist in analog format, such as video cassettes and books. And the digital works themselves, she said, are still generally unencrypted.
Even so, worries remain.
Siva Vaidhyanathan, a professor of information studies at the University of Wisconsin, said some sites now require visitors to agree to restrictions ahead of time - essentially signing away their fair use rights.
"As of today, the Internet is certainly providing a cornucopia of information," he said. "The question is, 'How long will it be this rich?"'
Electronic Frontier Foundation: http://eff.org
Recording industry: http://riaa.org
Movie industry: http://mpaa.org
U.S. Copyright Office: http://www.loc.gov/copyright