The U.S. Supreme Court voted 6-to-3 to uphold a law requiring the use of Internet filtering technology at public libraries that receive federal funding.

The decision in U.S. vs. American Library Association  (ALA) was announced Monday.

The justices ruled that the Children's Internet Protection Act (CIPA) does not violate First Amendment speech protections. CIPA requires libraries that receive federal assistance for Internet access to install software that blocks obscene or pornographic images.

The ruling overturned an earlier decision by the U.S. District Court for the Eastern District of Pennsylvania.

Writing for the majority, Chief Justice William Rehnquist said that the government's ability to attach conditions to the receipt of federal funding is well-established and that content filtering is "reasonable" given the dynamic nature of the Internet.

Rehnquist dismissed concerns about the tendency of Internet filtering software to "overblock" and prohibit access to constitutionally protected speech, citing the ease with which filtering software can be disabled. Rehnquist was joined in his opinion by Justices Sandra Day O'Connor, Antonin Scalia and Clarence Thomas. Justices Anthony Kennedy and Stephen Breyer agreed with the decision, but filed separate opinions in the case.

In his opinion, Kennedy wrote that the government has "substantial interests" in protecting minors from inappropriate material and said that those opposing CIPA failed to show that adult users' access to material is limited by the law. Filtering is appropriate so long as librarians retain the ability to unblock filtered material or disable Internet filtering software "without significant delay on an adult user's request," he said.

In a similar but separate opinion, Breyer cited the lack of alternatives to Internet filtering and the "comparatively small burden imposed (by filters) upon library patrons seeking legitimate Internet materials" as reasons for agreeing to overturn the lower court's opinion.

Dissenting from the majority ruling were Justices John Paul Stevens, David Souter and Ruth Bader Ginsburg, who found various aspects of the CIPA legislation limit access to constitutionally protected speech.

Noting that the current generation of filtering software relies on lists of keywords and phrases to block sites and cannot be tailored to target specific categories of images, Stevens wrote that CIPA "overblocks" legitimate content. Souter and Ginsburg cited vagaries in the CIPA legislation that call into question whether librarians "may" or "must" unblock sites for adults as grounds for declaring CIPA unconstitutional.

The IDG News Service is a Network World affiliate.