Belgian Internet Service Provider (ISP) Scarlet is appealing against a court ruling that said it must block illegal downloads from peer-to-peer networks and must begin doing so within six months.

Scarlet, formerly a wing of Italy's Tiscali, was ordered by Belgium's Court of First Instance in June to use Audible Magic software to scan peer-to-peer (P2P) network traffic and block files identified as containing unauthorized copyrighted material.

It marked the first time in Europe that an ISP was held responsible for the content of its subscribers' traffic.

However, the company has filed papers with the Brussels appeal court, in which it argues that ISPs are protected by laws deriving from the EU's E-Commerce Directive, which protect such "mere conduits" from liability for the content of their traffic.

This is despite an apparent contradiction with another EU Directive, the Copyright Directive, which gives copyright owners certain powers over intermediaries whose services are used for piracy.

Scarlet is being backed by the Belgian ISP Association (ISPA), which says the E-Commerce Directive's protection for ISPs must take precedence.

"The E-Commerce Directive needs to be seen as prevailing over the Copyright Directive," said ISPA head Geert Somers. "As a matter of fact I think that the relationship between various directives - the E-Commerce Directive, the Copyright Directive and the Intellectual Property Rights Enforcement Directive - will have to be further examined by the Court of Appeals."

The June ruling ordered Scarlet to install within six months filtering technology. The court even recommended that the ISP investigate Audible Magic, an audio fingerprinting application which dips into files as they are being transferred and tries to determine whether they are in fact copyrighted music; it can then block their transfer.

The lawsuit against Scarlet was originally filed in 2004 by the Belgian Society of Authors, Composers and Publishers (SABAM).