Emboldened by the takedown of Megaupload, the Motion Picture Association of America continues its crusade against file-sharing sites with its latest target, Hotfile, a file-sharing site. The MPAA, however, might have unexpectedly found itself in a bigger opponent than it bargained for as Google unexpectedly entered the legal fray by lending its clout and legal experience to Hotfile’s defense.

In the MPAA’s suit against Hotfile, Google submitted an amicus brief and cited that part of its success has relied on the “safe-harbor” protections allowed by the Digital Millennium Copyright Act. Google previously used the “safe-harbor” provision in its successful defense against a lawsuit filed by Viacom. In that case, which was thrown out in 2010, a federal judge ruled that Google was protected by the DMCA and could not be found liable for providing an online service on which individual users uploaded copyrighted content.

Going against Viacom’s claim that Google permitted copyrighted material to exist on YouTube while simultaneously profiting from it, Judge Louis L. Stanton of United States District Court for the Southern District of New York wrote, “The present case shows that the DMCA notification regime works efficiently: when Viacom over a period of months accumulated some 100,000 videos and then sent a mass take-down notice on February 2, 2007, by the next business day YouTube had removed virtually all of them.”

In the amicus brief, Google explains that the “safe-harbor” provision should be extended to protect Hotfile because, as evidenced in the Google’s Viacom case, the responsibility of policing the internet for copyright infringements should rest with the copyright owners and not with internet service providers.

The Hotfile case is slightly peculiar because Hotfile maintains that it doesn’t even support a search feature for its site, which distinguishes it from other file-sharing sites that have been successfully sued by copyright holders in the past.

That the courts retain a uniform interpretation of the DMCA’s “safe-harbor” provision is of utmost interest to Google’s case with Viacom, which is currently in appeal. Should a judge decide that the provision doesn’t provide legal protection to Hotwire, the ruling could open a nasty can of worms in Google’s defense against Viacom.

Google’s full amicus brief can be found below.

Google Amicus Brief PDF