Sam Gustin thinks this ain't over. The federal government is fighting the American Civil Liberties Union, and between them and the 3rd U.S. Circuit Court of Appeals, no one can agree on what constitutes pornography online and how it should be handled.

But one thing seems certain, at least for now: a major federal law designed to keep web porn away from kids is unconstitutional.

The 3rd U.S. Circuit Court of Appeals today upheld a lower court's decision that the Child Online Protection Act is unconstitutional. The Justice Dept. says it is reviewing its options, which could include an appeal to the U.S. Supreme Court.

The law, known as COPA, was originally passed in 1998 under the Clinton Administration, with the purpose of protecting minors from sexually explicit content on the Web. But because the law was immediately challenged in court, it has never taken effect.

COPA would require all website operators who display "material harmful to minors" to block minors from accessing those sites. The law, which defines "material harmful to minors" to be "prurient" content deemed to violate "contemporary community standards," would require website owners displaying such content to verify the age of all visitors through a method such as a credit card number.

Federal courts have repeatedly found the law unconstitutional, both because it is too broad, and because better methods of keeping adult material away from kids online exist, such as filters.

The Justice Dept. has vigorously defended the law. In 2006, the government subpoenaed Web search records from Google and other internet companies in an effort to show that the COPA would be more effective than filtering software, setting off a storm of protest. Google refused to cooperate. Ultimately, after a court limited the government's request to a sample of the Web pages in its index, Google complied.

In today's ruling, the court confirmed previous findings that COPA is not, in fact, the most effective way of keeping kids away from adult content online.

"Unlike COPA, filters permit adults to determine if and when they want to use them and do not subject speakers to criminal or civil penalties," the court ruled.

The ACLU hailed the ruling.

"For years the government has been trying to thwart freedom of speech on the Internet, and for years the courts have been finding the attempts unconstitutional," Chris Hansen, a lawyer for the group, said in a statement. "The government has no more right to censor the internet than it does books and magazines."

But the Justice Dept. sounded a bitter note.

"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.

Miller said the government is reviewing its options, which could include appealing the decision to the full Court of Appeals or the Supreme Court.