Yesterday US District Judge Marilyn Hall Patel issued a temporary restraining order, directing Napster not to facilitate or permit infringement of copyrighted material. Because the immensely popular person-to-person music trading service does not have the capability to separate copyrighted materials from non-copyrighted, this ruling will effectively shut down Napster at midnight tonight, pending the company's request in the 9th Circuit Court of Appeals in San Francisco for an emergency stay. The restraining order is seen as a major victory for the Recording Industry Association of America (RIAA), which sued Napster in December for copyright infringement. When the case began, Napster had a few hundred thousand users. It now has over 20 million and estimated that this number would grow to 75 million by year's end, when the full trial is scheduled. Judge Patel agreed with the RIAA's argument that allowing Napster to continue operating in the meantime would only increase the harm. The central issue in the case is the question of "fair use," especially as it was defined in a 1984 Supreme Court Case (Sony v. BetaMax) and the 1992 Audio Home Recording Act. Napster argues that the law does not specify the number of people with which someone may share purchased music. The RIAA counters that making purchased music available to millions of anonymous users does not constitute fair use and that it is simply unfair for Napster "to build a multi-billion dollar business on the backs of copyrighted works it doesn't own." Should the restraining order go into effect, it will certainly put a large dent in music trading online, as Napster is by far the easiest and most popular service. The MP3 genie, however, has left the bottle some time ago, and users in search of digital music have already begun to turn to different file-swapping technologies like Freenet and Gnutella, which do not rely on a central server and are thus almost impossible to police.