In what was possibly a fatal legal blow, Napster Inc. must stop allowing the millions of music fans who use its Internet-based service to share copyrighted material, according to a ruling handed down Monday by a San Francisco federal appeals court. "This is a clear victory," said Hilary Rosen, president and CEO of the Recording Industry Association of America (which had gone so far as to retain former presidential candidate and Viagra pitchman Bob Dole as a strategic advisor in the matter of Napster, according to Inside.com). "The court of appeals found that the injunction is not only warranted, but required. And it ruled in our favor on every legal issue presented." Napster officials announced on Monday that they would appeal the decision, which they had earlier said could jeopardize the company's very existence. In its own defense, Napster had argued that it could not be held responsible if its reputed 50 million subscribers used copyrighted material. "The court's decision . . . confirms that Napster was wrong in taking not only Metallica's music but (also that of) other artists who do not want to be a part of the Napster system," the hard rock band, Metallica, told Reuters. The landmark decision on Monday comes more than four months after an Oct. 2 hearing in which recording industry giants (including BMG, Warner, Universal, EMI and Sony) had demanded that Napster, which was created in 1999 by former Northeastern University student Shawn Fanning, now 20, be ordered to stop enabling users to swap songs for free.