A European Union court said Internet service providers cannot be required to install filters that would prevent the illegal downloading of files.
The ruling is a blow to artists who had sought to have their intellectual property rights protected that way.
SABAM, a Belgian company representing writers, composers and editors, established in 2004 that users of an Internet service provider called Scarlet Extended were illegally transferring files. A Belgian court ordered Scarlet to install at its own expense a system to make that impossible.
But the Court of Justice of the European Union ruled Thursday that this would require monitoring of all electronics communications of all of Scarlet's customers, infringing on their rights, and that it violates EU law.