The Recording Industry Association of America (RIAA) urged a federal appeals court to enforce a ruling that would shut down Napster's Internet-based music-file-sharing service, on Friday.

Napster is accused of flouting copyright laws because its service allows users to trade digital-music files.

The RIAA has found allies in the US government, the Motion Picture Association of America and the Business Software Alliance. Each filed friend-of-the-court briefs supporting the recording industry's case.

Correct In court on Friday, the RIAA argued that US District Court Judge Marilyn Hall Patel was correct when she ruled that Napster's file-swapping service contributes to large-scale copyright infringement. The organization asked that a preliminary injunction against the Napster be upheld.

The injunction required Napster to stop users trading copyrighted songs using its service. Napster replied that this was technically impossible, and would shut the service down. Napster then turned to the US Court of Appeals for the Ninth Circuit in San Francisco, which suspended the injunction pending the appeal’s outcome.

Napster's service allows users to trade digital-music files in violation of copyright laws, said the RIAA's lawyers. They added that Napster knowingly facilitates this illegal swapping with the intention of profiting from it. The RIAA lawyers said: "Every day, Napster enables, encourages and directly benefits from the infringement of 12 million to 30 million copyrighted works."

Theft The RIAA filed its lawsuit against Napster in December last year. Hilary Rosen, president and chief executive officer of the RIAA, said: "We are not suing a technology, we are suing a company that is stealing work that does not belong to them."

Napster denies the charges against it, and highlights perceived flaws in the lower court's ruling. The company’s lawyers argue that Judge Patel misinterpreted copyright laws in reaching her decision, and underestimated the impact file-sharing services will have on the Internet.

The company argues its service is protected by the Home Recording Act of 1992, which allows users to make recordings of music for personal use, but not for commercial distribution.

Support However, that defence suffered a blow on Friday when the US Copyright Office chimed in on the case. The government's brief argued that Napster's service is not protected by the Home Recording Act, in part because the Act does not apply to music that is copied using PCs and hard drives.

Napster attorney David Boies called the government's position "incorrect". The government's brief took no position on other matters Napster has raised in its defence, he noted, including Napster's claim that it is protected by the Digital Millennium Copyright Act and a 1994 case involving Sony’s Betamax video cassette recorder (VCR).

In that case, Sony was found not guilty of copyright infringement because VCRs can be used for legitimate purposes besides the illegal pirating of movies.

More support Also on Friday, two "amicus" briefs supporting the RIAA were submitted by the Motion Picture Association of America and Business Software Alliance - whose members include Adobe Systems, Apple and Microsoft. It is up to the appeals court how much weight they give to any of the amicus briefs submitted.

Napster isn't without advocates, in late August a broad coalition of industry groups representing high-technology and Internet companies filed a handful of amicus briefs with the appeals court, in which they make arguments that support Napster's defence.

Some of the groups involved, which include the powerful Consumer Electronics Association, echoed Napster's own arguments that Judge Patel misinterpreted copyright laws in reaching her ruling. They also contend that, if left to stand, her ruling against Napster will establish a troublesome precedent that could stifle the development of Internet services and technologies.