A divided Supreme Court ruled yesterday that Congress can force the nation's public libraries to equip their computers with internet filtering software.

The blocking technology, intended to keep children from accessing pornographic web sites, does not violate the First Amendment even though it shuts off access to some legitimate, informational web sites, the court ruled.

Because libraries can disable the filters for any patrons who ask, the system is not too burdensome, the court said.

The 6-3 ruling upholds a 2000 law—the Children's Internet Protection Act (CIPA)—that requires libraries to install filters or surrender federal funding, including eRate discounts on telecommunications services and internet access. Four justices said the law was constitutional, and two others said it was allowable as long as patrons were not denied access to legitimate web sites.

The law applies to schools as well, but only its application in public libraries was challenged in court. Nevertheless, many school leaders were watching the high court's deliberations closely, believing that a rejection of the law could open the door to legal challenges of CIPA as it applies to schools.

The ruling was a victory for Congress, which has struggled to find ways to shield children from pornographic internet sites. Congress has passed three laws addressing the issue since 1996; the first was struck down by the Supreme Court and the second was blocked by the court from taking effect.

The first two laws dealt with regulations on web site operators. The latest approach, in the 2000 law, mandated that public libraries put blocking technology on computers as a condition for receiving federal money. Since 1999, libraries reportedly have received about $1 billion in eRate subsidies, which are paid for by fees collected from telecommunications carriers.

The government had argued that libraries don't have X-rated movies and magazines on their shelves and shouldn't have to offer access to pornography on their computers.

Librarians and civil liberties groups countered that filters amount to censorship because they inadvertently block access to valuable—and constitutionally protected—information.

A three-judge federal panel in Pennsylvania ruled last year that the law was unconstitutional because it caused libraries to violate the First Amendment. The filtering programs block too much nonpornographic material, the panel found.

The Supreme Court disagreed. Chief Justice William H. Rehnquist said the law does not turn librarians into censors. Rehnquist's opinion was joined by Justices Sandra Day O'Connor, Antonin Scalia, and Clarence Thomas.

Justices Anthony M. Kennedy and Stephen Breyer, in separate opinions, said the government's interest in protecting young library users from inappropriate material outweighs the burden on library users of having to ask staff to disconnect filters.