Napster had no immediate comment on the ruling. In a written statement, the Recording Industry Association of America (RIAA), a trade group representing the major record companies, called the ruling a "strong endorsement" of its position on file blocking and praised the court's decision.
Last July, Napster closed the doors on its MP3 file-trading network, which at its height claimed as many as 60 million users, after a barrage of lawsuits from record companies and their trade group, the RIAA. The suits led to a court order requiring the shutdown until Napster could stop the trading of copyright work.
Before its shutdown and as a result of those suits, the company had been engaged in a series of attempts to filter copyright works from its service and had wrangled in court with the record companies over how the RIAA would deliver to Napster information about what files would have to be filtered out.
The ruling came on Napster's appeal of US District Judge Marilyn Hall Patel's order last year to continue its file-blocking efforts.
Napster had argued to the appeals court that Patel's ruling was vague, that the court lacked the authority to modify its initial injunction against the company, that the shutdown order was too harsh and that Patel used a technical advisor inappropriately in arriving at the ruling.
In order to overturn Patel's rulings, the appeals court would have had to find that she committed legal errors.
The court denied all of Napster's motions. "The terms of the preliminary injunction are not vague and properly reflect the relevant law on vicarious and contributory copyright infringement. The shut down order was a proper exercise of the district court's power," it said.
In January, Napster began beta testing a new service, one in which users pay for access and trade copy-protected songs.