A US appeals court has reversed a four-year-old order banning the publication of the computer code which can be used to copy DVDs.
The court reversed a 1999 injunction favouring the DVD Copy Control Association (DVD CCA), which had filed a lawsuit against California resident Andrew Bunner, accusing him of violating its intellectual property rights by posting DeCSS (De-Content Scrambling System) software on his website.
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The court ruled that "the preliminary injunction... burdens more speech than necessary to protect DVD CCA's property interest and was an unlawful prior restraint upon Bunner's right to free speech".
Last month, the DVD CCA, representing motion picture and consumer electronics companies, had asked the California Superior Court to dismiss its lawsuit, but Bunner opposed such a move.
The court denied the motion for dismissal as it felt that the appeal presented "important issues that could arise again and yet evade review".
DeCSS allows users to access movies on DVDs that are protected by the CSS encryption technology.
The code was first published by a Norwegian teenager, Jon Lech Johansen, also known as DVD Jon, who was acquitted of all charges in a Norwegian court last year.
That ruling was then upheld by the Oslo Court of Appeals in December, which found that Johansen had not used DeCSS to make DVD copies in violation of intellectual property regulations, and that is was not his intention to make illegal DVD copies.
The California Supreme Court had originally granted an injunction against publishing DeCSS based on a decision that the software contains trade secrets found in the CSS technology, and that those secrets should be protected by law.
The Appeals Court, instead, ruled that there was no evidence that CSS was still a trade secret when Bunner posted DeCSS, as it had been available on thousands of websites around the world.
However, the ruling will not necessarily make it legal in California to post DeCSS online in the future.
The court stressed that their ruling was "not a final adjudication on the merits. The ultimate determination of trade secret status and misappropriation would be subject to proof to be presented at trial".
But the ruling is a victory for free speech advocates groups that have been caught up in the aggressive campaign by Hollywood studios to prevent DVD copying with encryption technology.
The DVD CCA said it was disappointed by the California Court of Appeals ruling and that the group is taking into consideration, but has yet to decide its "next steps in this case".
Laura Rohde writes for IDG News Service