Representatives from the American Civil Liberties Union went before the 3rd U.S. Circuit Court, urging judges hearing the matter to uphold a ban on COPA, which would impose draconian criminal sanctions.
Under the law - which was created long before the days of chat rooms, YouTube and other interactive sites the law does not address - those convicted could face fines up to $50,000 per day and up to six months in prison for online material acknowledged as protected for adults but deemed "harmful to minors."
The judges hearing the case questioned the law's effectiveness, 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 argued that Internet filters block 95 percent of offensive content and can be set according to a child's age or a parent's judgment. Federal attorneys argued that only about half of all families use Internet filters.
The three-judge panel did not indicate when it would issue a ruling.
A federal judge declared the law unconstitutional in 2007. The Department of Justice is hoping to overturn that ruling.
The law has never 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.