Judge Louis Stanton said in the ruling, the provider must know of the particular case before he can control it, the provider need not monitor or seek out facts indicating such activity.

Google hailed the decision and said in a news release, the decision was an important victory not just for us, but also for the billions of people around the world who use the web to communicate and share experiences with each other. Google also said, the ruling means YouTube is protected by the safe harbor of the Digital Millennium Copyright Act.

Viacom, an entertainment giant that owns Paramount Pictures, DreamWorks and a number of cable channels, had alleged that YouTube, which Google bought in 2006, built itself into a successful video-sharing site by promoting the unlicensed use of video taken from Viacom cable channels such as MTV, Comedy Central and Nickelodeon. Viacom had originally sued Google in 2007, alleging massive copyright infringement on YouTube and seeking $1 billion in damages.

Google, which acquired YouTube for $1.65 billion, recognized the possibility that the video site would one day be forced to wage lengthy court battles. Meanwhile, Google has successfully negotiated licensing deals with many entertainment companies, including Warner Music Group, CBS and most recently, the BBC.