The Supreme Court today decided that Internet service providers cannot be held liable for their customers’ copyright infringement unless they take specific steps that cause users to violate copyrights. The court ruled unanimously in favor of Internet provider Cox Communications, though two justices did not agree with the majority’s reasoning.

The ruling effectively means that ISPs do not have to conduct mass terminations of Internet users accused of illegally downloading or uploading pirated files. If the court had ruled otherwise, ISPs could have been compelled to strictly police their networks for piracy in order to avoid billion-dollar court verdicts under the Digital Millennium Copyright Act (DMCA). //

The court decided today that a service is tailored to infringement if it is not capable of “substantial” or “commercially significant” noninfringing uses. The court cited Sony’s 1984 victory in the Betamax case, in which justices found that the Betamax was capable of noninfringing uses and that Sony’s sale of it did not constitute contributory infringement. Sony’s win in 1984 thus contributed to its loss today.