The Electronic Frontier Foundation, along with several other groups including the American Library Association, urged an appeals court in the US to uphold a ruling in a long-running suit related to secondhand software sales.

The groups say that if the ruling is overturned, secondhand sales of copyright items including books and CDs could become illegal.

Late last year, a judge in the US District Court for the Western District of Washington ruled in favour of Timothy Vernor, a man who tried to sell legitimate versions of Autocad software on eBay. Autodesk complained that Vernor was not authorized to sell the software, and eBay ultimately banned Vernor from its site.

Vernor took Autodesk to court, arguing that since he was selling legitimate versions of the software he hadn’t violated any laws. Autodesk contends that it doesn’t actually 'sell' software, but licenses it and prohibits buyers from reselling it.

But in October, the judge decided that no matter how Autodesk describes its agreement with customers, it is indeed transferring ownership of the product to buyers.

"A person who buys a home is nonetheless restricted in his use and subsequent transfer of the home by property laws, zoning ordinances, and fair housing statutes," Judge Richard Jones wrote in his ruling. "No one would characterize the person's possession, however, as something other than ownership.

The judge also agreed with Vernor's argument that owners of software have "first sale" rights under copyright law, which entitles them to "sell or otherwise dispose of" the copy they bought.

Autodesk appealed the decision.

On Thursday, the EFF, the Consumer Federation of America, the American Library Association, Association of Research Libraries, Association of College and Research Libraries, US Public Interest Research Group, and Public Knowledge filed a brief with the US Court of Appeals for the Ninth Circuit urging it to uphold the ruling.

The groups say they worry about the precedent that could be set if the ruling is overturned. “The position pressed by Autodesk here would jeopardize not only the interests of consumers of software, but also those who rely on libraries, used bookstores, video rental services, and online auctions to borrow, buy, or sell books, music, films, video games, and other copyrighted works,” the filing reads.