Companies can enjoy the security for their creative works that Congress meant them to have

Charles Sims, lawyer

It then went on to spread to many other sites. Johansen said he created it to allow people using the Linux operating system to use DVDs.

The court said that DeCSS was "like a skeleton key that can open a locked door, a combination that can open a safe, or a device that can neutralise the security device attached to a store's products".

Pirate film copies are already a growing concern for the movie industry.

'Happy'

Earlier this week customs officers in Hong Kong arrested 10 people and seized 200 pirated copies of the Harry Potter film from shops and markets in the territory.

Video CDs (VCDs) of the film have been on sale for 20 Hong Kong dollars (�1.80), and have also appeared in other Chinese cities plus Malaysia and Taiwan.

The court ruling marks a victory for the film studios and could have an impact on digital copyright laws of the future.

Charles Sims, lawyer for the film studios, said: "We couldn't be happier that the court of appeals has completely vindicated the DMCA and thereby enabled content companies to enjoy the security for their creative works that Congress meant them to have."

However Cindy John, attorney for the Electronic Frontier Foundation, said of the decision: "In the long run...I think it is going to mean that if anybody wants to create a new technology that in some ways enhances our ability to listen to or hear any copyrighted content they are going to have to go and beg permission from the movie industry..those industries are very reticent to embrace new technologies."

Rights

The DCMA was brought about in an attempt to strengthen copyright laws with regard to digital formats.

This is the first major challenge to the act although freedom of speech activists and scientists wishing to publish new technology research have argued it infringes on the freedom of speech provisions within the US Constitution.

Two other DMCA-related cases also came before the courts this week.

In San Francisco a lawsuit was filed against a web-publishing group who had posted details of descrambling software online.

Meanwhile in Trenton, New Jersey, a case concerning scientific research into the technology used for preventing music piracy was heard.