A US federal judge in Washington wrote that a suspected net pirate shouldn’t be prosecuted only because the IP address of his computer was identified by a film studio. The watershed opinion may tip the fortunes of defendants in similar scenarios.

An IP address could be likened to the internet fingerprint of a computer; each is unique from.

Copyright holders trying to take offenders to court regularly set fake picture files online, record the hundreds or thousands of IP addresses that download it, then supply that info to the courts in an effort to spot and sue hapless users on the different side of the display.

The studio claimed that “the defendants either downloaded the pirated movie themselves, or allowed, eased, or encouraged the use of their Internet connections by other people to download the movie,” according to TorrentFreak.

Washington District Judge Robert Lasnik said that the justification is not sufficient, in part for the reason that it starts with the premise of guilt. As the states described in charge section b were too obscure ruling on a motion Lasnik sided against the defendants.

“[The movie studio] has really alleged no more than the named defendants bought Internet access and did not make sure that others didn’t utilize that accessibility to download copyrighted content,” the judge wrote.

Lasnik also said that there clearly was no evidence the man who could end up facing a suit was in fact the man who selected to download the copy of ‘Elf Man.’

“While it’s perhaps that the subscriber is the person who participated in the BitTorrent swarm, it’s also possible that a relative, guest, or freeloader engaged in the infringing actions.”

Other judges presiding over similar cases previously have agreed with Lasnik, developing a precedent that’s required copyright enforcers before trying to start a case to narrow down their record of defendants.

This past year, a Sydney-based law firm disclosed that courts in both Australia as well as the US have refused to turn over private details of web users who downloaded content without permission.

What this means is that each user of every device (computer, iPad, iPhone, etc) linked to that WiFi connection will make use of the exact same IP address. Even a random passerby getting the WiFi network would use the exact same IP address,” attorneys from Marque Attorneys wrote, as quoted by TorrentFreak.