The US Supreme Court has narrowly ruled that a law meant to protect children from online pornography is probably an infringement of free speech.
The law was passed in 1998 but never came into effect
Five of the court's nine judges opposed the law, which was passed in 1998 and is backed by the Bush administration.
The majority said a lower court was right to block it, as it may have violated the First Amendment of the US Constitution on freedom of speech.
The case has been sent back to a lower court for a trial.
A new trial will allow the court to discuss any technological developments that may permit adults to see and buy legal material - while keeping it away from children.
The law, known as the Child Online Protection Act (COPA), was signed by then-President Bill Clinton in 1998, but blocked by a federal judge five years ago.
It would have required adults to use a form of online registration to access objectionable material.
The law would have allowed fines of up to $50,000 for placing material that is "harmful to minors" within easy reach on the web.
Filtering software "is not a perfect
solution to the problem of children gaining access to
harmful-to-minors materials," Justice Anthony Kennedy stated.
The American Civil Liberties Union and other critics of
the law argued it would restrict too much material that adults might legally see and buy.
"By preventing Attorney General [John] Ashcroft from enforcing this questionable federal law, the Court has made it safe for artists, sex educators, and web publishers to communicate with adults about sexuality without risking jail time," ACLU Associate Legal Director Ann Beason said in a statement in reaction to the decision.
But Stephen Breyer, one of the four dissenting judges, said prosecutors had been deprived of an "important weapon".
Justice Department spokesman Mark Corallo also criticised the decision.
"Our society has reached a broad consensus that child
obscenity is harmful to our youngest generation and must be
stopped," he said.
"Congress has repeatedly
attempted to address this serious need, and the court yet
again opposed these common-sense measures to protect
This is the third time that the Supreme Court has addressed the question of what Congress may do to limit children's exposure to pornography on the internet.
In 1997, the court struck down a broader law, the 1996 Communications Decency Act (CDA), as a violation of the First Amendment, the newspaper said.
COPA attempted to fix the CDA's constitutional defects, but it too was found unconstitutional in 2000 by an appeals court.
In 2002, a divided Supreme Court told the court to reconsider its decision. But last year, the same court struck down the law again - and the Bush administration appealed the case once more to the Supreme Court.