In 2007 Viacom filed a one billion US dollar lawsuit claiming that YouTube had infringed its copyright.

On 23 June 2010 the US District Court in New York ruled in favour of YouTube, finding that it qualified for safe harbour protection under §512(c)(1)(A) of the Digital Millennium Copyright Act (DMCA): The Court held that general awareness of pervasive copyright-infringement does not impose liability on the service provider. Knowledge of specific and identifiable infringements of particular individual items is required.

This ruling was partially reversed on 5 April 2012 by the US Court of Appeals for the Second Circuit. While the Appeals Court affirmed the requirement of knowledge or awareness of specific infringing activity, but ruled that the finding for YouTube was premature and sent the case back the lower court.

The US District Court now confirms its earlier judgment that YouTube qualifies for safe harbour protection. The Court makes clear that the burden of proof lies on the copyright owner and finds that the DMCA notification regime is "entirely workable". The Court rules that YouTube showed no wilful blindness to specific infringements and finds that YouTube did not have the right or ability to control the infringing activity: knowledge of the prevalence of infringing activity, and even welcoming it, does not itself forfeit the safe harbour. To lose that protection, the provider must influence or participate in the infringement.

Viacom has announced that it will appeal this decision. The legal battle continues...