Regarding Napster's claim that its users were not infringing copyright because sharing copyrighted musical compositions and sound recordings via the Napster service is protected by the "fair use" doctrine, the court held that the four fair use factors in the Copyright Act tip the balance in the record companies' favour.

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The defense is hoping that "the Second Circuit or the Supreme Court will see that this restriction on fair use of media doesn't fit with the copyright clause in the Constitution, " she said.

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In fact a balanced copyright system, including fair use, is one of the key reasons why products like search engines, YouTube, Facebook, and thousands of other Internet companies are commercially viable in the first place.

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Many people have converted CDs they have bought to MP3 audio files and then shared them with other people in defiance of copyright laws, which place restrictions on the "fair use" of purchased music.

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David Cameron pointed to the " fair use" doctrine in American law, which he said had allowed companies like Google to flourish without fear of infringing copyright.

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