A Bush administration official urged the Supreme Court on Wednesday to revive a law that would require the nation's public libraries to install software filters on their computers to screen out pornography.
Last year, a special federal court in Philadelphia ruled that the law violated principles of free speech and blocked it from taking effect.
In Wednesday's argument before the Supreme Court, U.S. Solicitor General Theodore B. Olson said libraries routinely buy certain books but not others, and do not regularly stock pornographic books, Hustler magazine or X-rated videos.
The same discretion should guide their handling of the Internet, he said. "The 1st Amendment does not require libraries to sponsor the viewing of pornography," Olson said.
Two years ago, Congress said if libraries receive federal funds, they must install software filters.
Most of the justices sounded supportive of the law.
"They say some of this is garbage, and we don't want it," Justice Antonin Scalia said.
"What's the great burden on speech?" Justice Stephen G. Breyer asked. Adults can ask librarians to disable the filter if they are doing research on Web sites that may be screened out, he said.
Paul Smith, a lawyer for the American Library Assn., said patrons who ask to have the filter disabled would face a "stigma."
The library group also argued that while librarians and library boards can adopt screening rules for their computers, Congress should not impose a national rule from Washington.
"The federal government has no business using its spending power to ... push librarians from their professional judgment," Smith said. "A library is very much like a public university, a place for free expression."
About 7% of the nation's libraries put software filters on their computers.
In their ruling last year, the judges in Philadelphia said the filters were too clumsy. Tens of thousands of Web sites were excluded -- some for obvious, but perhaps mistaken, reasons and others more mysteriously.
Travel sites showing sunbathers on beaches were screened out as pornography. So too was the Web site of the Southern Alberta Fly Fishing Outfitters and the fans' page for the Toronto Maple Leafs hockey team, the judges said.
However, the Supreme Court justices said the shortcomings of the filters did not call for striking down the law.
"The technology that's available now is not perfect," Justice Sandra Day O'Connor said, but it succeeds in excluding most of the pornography that is harmful to children.
The court will hand down its ruling in U.S. vs. ALA in several months.