The law never has been enforced because sexual health sites, Salon.com and other web publishers sued and won a temporary injunction that the U.S. Supreme Court later upheld. The law was declared unconstitutional with a permanent injunction last year, and that decision was appealed by the Justice Department.
COPA would make it a crime for web publishers to let children access material deemed "harmful to minors" by "contemporary community standards." The sites would be expected to require a credit card number or other proof of age. COPA does not cover chat rooms, You Tube and other interactive sites that emerged since it was passed. Penalties include a $50,000 fine and up to six months in prison.
The 3rd U.S. Circuit Court of Appeal judges hearing the current case have questioned whether COPA would be effective, given estimates that half of all online porn is posted overseas, beyond the reach of U.S. law.
Lawyers with the American Civil Liberties Union, representing Salon.com and other sites that initially challenged the law, argue that Internet filters block 95 percent of offensive content, and can be set to match a child's age or a parent's judgment.
But only half of all families use them, Justice Department lawyer Charles Scarborough countered.
"If there is nothing that works perfectly here, why not go with the thing that least offends the Constitution?" Judge Thomas L. Ambro asked.
Scarborough argued that the nation needs "a belt and suspenders approach" to the complex problem.
The three-judge panel did not indicate when it would rule.