Opinion of the Court
Id., at 75–76. StreamCast not only rejected another company’s offer of help to monitor infringement, id., at 928–929, but blocked the Internet Protocol addresses of entities it believed were trying to engage in such monitoring on its networks, id., at 917–922.
B
After discovery, the parties on each side of the case cross-moved for summary judgment. The District Court limited its consideration to the asserted liability of Grokster and StreamCast for distributing the current versions of their software, leaving aside whether either was liable “for damages arising from past versions of their software, or from other past activities.” 259 F. Supp. 2d 1029, 1033 (CD Cal. 2003). The District Court held that those who used the Grokster and Morpheus software to download copyrighted media files directly infringed MGM’s copyrights, a conclusion not contested on appeal, but the court nonetheless granted summary judgment in favor of Grokster and StreamCast as to any liability arising from distribution of the then current versions of their software. Distributing that software gave rise to no liability in the court’s view, because its use did not provide the distributors with actual knowledge of specific acts of infringement. Case No. CV 01 08541 SVW (PJWx) (CD Cal., June 18, 2003), App. 1213.
The Court of Appeals affirmed. 380 F.3d 1154 (CA9 2004). In the court’s analysis, a defendant was liable as a contributory infringer when it had knowledge of direct infringement and materially contributed to the infringement. But the court read Sony Corp. of America v. Universal City Studios, Inc., 464 U.S. 417 (1984), as holding that distribution of a commercial product capable of substantial noninfringing uses could not give rise to contributory liability for infringement unless the distributor had actual knowledge of specific instances of infringement and failed to act on that knowledge. The fact that the software was capable of substantial noninfringing uses in the Ninth Circuit’s view meant
