A U.S. Federal Court has struck down a law meant to block children from viewing internet pornography, saying it violates constitutional free speech protections.

The ruling sided with a challenge by the American Civil Liberties Union, which had argued statutes of the Child Online Protection Act were too restrictive.

In his decision, Senior U.S. District Judge Lowell Reed Jr. expressed support for the principle behind the law, but found fault with the extent to which it restricts free speech.

"Perhaps we do the minors of this country harm if [free speech] protections, which they will with age inherit fully, are chipped away in the name of their protection," he wrote.

Reed also noted alternative methods, including software filters, which can prevent children from accessing online pornography.

Government lawyers disagreed, saying such filters are often complicated and ineffective.

Peter D. Keisler, who represented the government, also argued filters place too much responsibility on parents.

"It is not reasonable for the government to expect all parents to shoulder the burden to cut off every possible source of adult content for their children, rather than the government's addressing the problem at its source," he said in a post-trial brief.

Pitfalls of pornography laws

The decision strikes down a 1998 law punishing commercial website operators who allow access to material deemed "harmful to minors" by "contemporary community standards."

The sites would have been expected to require a credit card number or other proof of age. Penalties included a $50,000 fine and up to six months in prison.

In 1996, Congress launched a failed attempt to ban online pornography, but the following year, the Supreme Court ruled the law was constitutionally vague and overly restrictive.

The 1998 law narrowed the restrictions to commercial websites and defined indecency more specifically.

With files from the Associated Press