The U.S. Supreme Court, on a 6-3 vote, ruled Monday that public library Internet anti-pornography filters are not a violation of the First Amendment, even if the filters block some legitimate sites. The decision overturns a Philadelphia federal appeals court ruling that the Children's Internet Protection Act (CIPA) violated the free speech rights of Americans.

CIPA was enacted in December 2000, in part to protect minors from access to Internet pornography. It requires schools and libraries to use the filtering software to shield minors from adult material but, because it called for adults to get permission to access certain information, it raised the ire of the civil liberties and library groups. The law also blocked federal funding to libraries that did not install the software.

The Philadelphia appeals court sided with the civil liberties groups, saying it was concerned that library patrons might be too embarrassed or lose their right to anonymity because the CIPA law required that they seek permission to have the filtering software removed.

The Supreme Court dismissed those concerns and additionally ruled that the filters do not turn libraries into online censors.

The decision was a major victory for federal lawmakers, who have made three attempts to curb children's access to online pornography. In 1996, Congress passed the Communications Decency Act (CDA), which the Supreme Court struck down in 1997 as unconstitutional, saying the CDA "place(d) an unacceptably heavy burden on protected speech."

Congress followed that defeat with the 1998 Child Online Protection Act (COPA), which required commercial Web site operators to use credit cards or other adult access systems to prevent minors from viewing the material. The Supreme Court found that law was too broad in scope for practical enforcement.

CIPA, on the other hand, focused on requiring libraries to install anti-pornography filters. The American Civil Liberties Union (ACLU) and the American Library Association filed twin-lawsuits last to have the law tossed out on First Amendment and due-process grounds.