A Belgian Internet service provider has appealed a ruling that it must block illegal file-sharing on its network in a case that tests two European Union directives concerning copyright and the extent of responsibility that ISPs have for transmitted content.

The appeal contests a ruling in June by Belgium's Court of First Instance against Scarlet Extended, an ISP formerly owned by Tiscali. Scarlet Extended was ordered to install within six months filtering technology made by software vendor Audible Magic Corp. The company makes software that can identity and block copyright content based on the characteristics of a file, which it calls "digital fingerprints."

The ruling has brought into focus two E.U. directives, which E.U. states are required to incorporate into their national laws.

While the E.U. E-Commerce Directive says that ISPs are mere conduits and not liable for monitoring content on their networks, the court disagreed, ruling that filtering is not the same as monitoring.

"It's a distinction that the judge makes with very little explanation," said Struan Robertson, senior associate with Pinsent Masons and editor of the legal Web site Out-law.com. The judgment "simply says the mere conduit defense is irrelevant in the circumstances."

The judgment appears to reinforce the E.U.'s Information Society Directive, also known as the copyright directive, which says a copyright owner should be able to obtain an injunction against an intermediary that's used for piracy.

While the International Federation of the Phonographic Industry said after the June ruling the case could set a precedent, it's unclear how the case could influence other European piracy-related cases.

"Outside Belgium, other courts might be influenced by this ruling, but they are not bound by this ruling," Robertson said. "Other courts with the same facts might come to a different conclusion."

The lawsuit against Scarlet Extended was originally filed in 2004 by the Belgian Society of Authors, Composers and Publishers, known as SABAM. The organization requested an injunction against Scarlet Extended, then known as Tiscali, for allowing music files to be traded on peer-to-peer networks.