(PHILADELPHIA, PA) -- a two-week federal trial to determine how far the government can go to protect children from pornography on library computers ended on Thursday with judges openly concerned about whether the latest online smut law from Congress infringes on free-speech rights.

The Children's Internet Protection Act or CIPA, which supporters view as the government's best shot yet at reining in online smut, requires public libraries to install filtering software on all computers or lose federal technology funding.

Attorneys for a plaintiffs' coalition of libraries, library patrons and Web site operators, who want CIPA overturned, said in closing arguments that libraries cannot implement the law without denying patrons their First Amendment right to free speech under the U.S. Constitution.

"We're stuck right in the heart of the First Amendment when we're talking about libraries," observed 3rd U.S. Circuit Court of Appeals Chief Judge Edward Becker.

Becker heads a three-judge panel that will rule by early May on a plaintiffs' request for a permanent injunction against CIPA. Whichever way the ruling goes, the case will be appealed directly to the U.S. Supreme Court.

A key plank in the case against CIPA is the limitations of filtering software products such as CyberPatrol, SmartFilter, WebSense, and N2H2, which are designed to block access to Web sites deemed harmful to children under 17, including more than 100,000 sites with sexually explicit content.

But even the government's attorneys concede that no product on the $250 million filtering software market can screen out objectionable Web sites without also blocking constitutionally protected sites including those of Sports Illustrated, Planned Parenthood and Salon.com.

The law's "terms, if you will, are a sham. Everybody knows you can't comply with its terms," American Civil Liberties Union attorney Chris Hansen told the court.

U.S. District Judge Harvey Bartle appeared to agree. "Every witness has testified that the statute can't be applied according to its own terms," he said.

Judges also seemed concerned that the decision about which of the 11 million World Wide Web sites deserve to be blocked is made by anonymous corporate officials who consider their choices to be vital trade secrets.

*** 'Nameless, Facelss' ***

"The nameless and faceless," intoned U.S. District Judge John Fullam. "What right does the government have to require this kind of filtering system?"

CIPA, the third attempt by Congress to control online pornography, was theoretically designed to weather free speech challenges by seeking only to cut off federal library funds rather than impose direct censorship restrictions.

At stake for the nation's 40,000 public libraries are hundreds of millions of dollars in subsidies, such as grants provided under the Library Service and Technology Act, which are used to automate services and pay for Internet access.

But the case also goes to the heart of the role libraries play as an open source of information in their communities.

The judges expressed empathy for communities that want to protect children from an aggressive commercial pornography industry intent on luring young customers. However, they also recognized the constitutional dangers of leaving censorship decisions to the local majority opinion.

Among the legal issues before the panel is whether judges can overturn CIPA without also branding unconstitutional the filtering systems already in place at libraries in Greenville, South Carolina, and Tacoma, Washington, which both provided evidence and testimony for the government's defense.

"There is no constitutional right to immediate, anonymous access to speech, for free, in a public library," Justice Department attorney Rupa Bhattacharya said in a spirited defense of CIPA that equated filtering software usage to the choices libraries make selecting books for their collections.

"Even if you assume that libraries have a right to provide unfettered access to the Internet, they don't have a right to do so with a federal subsidy," she added. "The crux of this matter is whether or not Congress has the power to decide how to use its money."

The first attempt by Congress to control online smut, the 1996 Communications Decency Act, was thrown out by the Supreme Court as an infringement of free speech. The second, the 1998 Child Online Protection Act, remains sidelined by an injunction with the U.S. high court due to issue a final opinion by mid-year. Both would impose criminal penalties on violators.