Napster has made its next move for survival in its battle with the Recording Industry Association of America (RIAA).

The RIAA, representing several major music labels, is fighting to close down the music-swapping site.

Late on Friday night, Napster's lawyers released a copy of a much anticipated brief that spells out the company's objections to Chief U.S. District Court Judge Marilyn Hall Patel's injunction against the site.

The judge's July decision announced in the Northern District of California had the potential of forcing Napster to remove all music by artists represented by the record labels that are part of the suit.

While an appeal against the judge's injunction allowed Napster to temporarily continue operations, the Friday brief is part of the company's attempt to remove any question of the legal validity of the system it uses - namely non-commercial peer-to-peer file sharing of copyrighted and/or not copyrighted material.

In the brief, Napster outlined several key objections to the judge's ruling, saying that it would be impossible to comply with the judge's order to remove the designated, copyrighted files.

The company contends that the architecture of the Napster model makes identifying copyrighted and not copyrighted material extremely difficult.

In addition, lawyers representing the music-trading site argued that Judge Patel did not adequately consider past legal precedents applicable to the case and that Patel underestimated the impact of peer-to-peer file sharing in the Internet marketplace.

The RIAA, representing several major music labels in the suit, objects to the trading of files where the plaintiffs in the case own the copyright.

Napster, however, contends that all of the file swapping operates on a non commercial basis and is directly done by users and not the company itself.

However leading legal eagles are questioning Napster’s arguments.

Leonard Rubin, head of intellectual property for Chicago law firm Gordon & Glickson LLC, said that Judge Patel's request to distinguish between the copyrighted titles and those not owned by the music labels traditionally holds a fair amount of merit in similar types of cases.

He noted that Napster's defence on these grounds would probably only stand if the company could show that the effect of altering the technology would be devastating to a large segment of society.

Rubin said the company would need to demonstrate that changing the technology, which Napster created, would be unfair to society as a whole.

"It seems that it is a weak point to raise," Rubin said.