The decision by the 3rd U.S. Circuit Court of Appeals in Philadelphia is the latest twist in a decade-long legal battle over the Child Online Protection Act. The fight has already reached the Supreme Court and could be headed back there.
The law, which has not taken effect, would bar Web sites from making harmful content available to minors over the Internet. The act was passed the year after the Supreme Court ruled that another law intended to protect children from explicit material online - the Communications Decency Act - was unconstitutional in the landmark case Reno v. American Civil Liberties Union.
The ACLU challenged the 1998 law on behalf of a coalition of writers, artists, health educators and the publisher Salon Media Group.
ACLU attorney Chris Hansen argued that Congress has been trying to restrict speech on the Internet far more than it can restrict speech in books and magazines. But, he said, "the rules should be the same."
Indeed, the Child Online Protection Act would effectively force all Web sites to provide only family-friendly content because it is not feasible to lock children out of sites that are lawful for adults, said John Morris, general counsel for the Center for Democracy & Technology, a civil liberties group that filed briefs against the law.
In its ruling Tuesday, the federal appeals court concluded that the Child Online Protection Act is unconstitutionally overly broad and vague. The court also ruled that the law violates the First Amendment because filtering technologies and other parental control tools offer a less restrictive way to protect children from inappropriate content online.
Morris argued that filters also provide a more effective way to protect children since they can block objectionable Web sites that are based overseas, beyond the reach of U.S. law.
For its part, the Justice Department said it will review the ruling before deciding its next step.
"We are disappointed that the court of appeals struck down a congressional statute designed to protect our children from exposure to sexually explicit materials on the Internet," said department spokesman Charles Miller.
If the case ends up before the Supreme Court, it would not be the first time that the justices have considered the Child Online Protection Act. In 2004, the high court upheld a ruling that the law violates the First Amendment. But the Supreme Court sent the case back to the district court to determine whether any changes in blocking software would affect the law's constitutionality.