A federal judge on Wednesday granted Google's motion for summary judgment, finding that the company had taken sufficient steps to deal with infringing content to meet the safe harbor requirements of the Digital Millennium Copyright Act.
Google VP and general counsel Kent Walker characterized the decision as "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."
A spokesperson for Viacom wasn't immediately available.
In a statement obtained by The Wall Street Journal's All Things Digital Web site, Viacom promised to appeal the decision.
Viacom has maintained throughout the legal proceedings that Google executives knowingly allowed copyrighted content to persist on YouTube as a means of ensuring the site's popularity.
Eric Goldman, associate professor of Law at Santa Clara University School, said in a phone interview that Viacom's appeal could take years and until that time, "this becomes the latest high-water mark in user-caused copyright infringement cases."
In an analysis of the decision posted on his blog, Goldman says that the ruling endorses industry-standard takedown practices and frustrates efforts by content owners to narrow DMCA safe harbor protections.
Online companies accused of copyright infringement as a result of actions by their users will be able to point to this decision to bolster their defense.
The Google-Viacom decision stands in stark contrast to an Italian court's ruling in February that found fault with Google's video takedown procedures. A judge in Milan convicted three Google executives of privacy law violations for failing to quickly remove an offensive video posted to YouTube's Italian site.
Google called that decision "deeply troubling" and is appealing.
Though the Italian case involves privacy rather than copyright law, both cases raise questions about the amount of vigilance that Internet content hosts are expected to exercise over user-submitted content.
In the U.S. at least, Google and its services that involve user-submitted content now look to be on more stable legal footing.