Internet service providers cannot be forced to block their users from downloading songs illegally, as such an order would breach EU rules, Europe's highest court said on Thursday in a ruling welcomed by a consumer group.

The Luxembourg-based EU Court of Justice (ECJ) issued its verdict in a case involving Belgian music royalty collecting society SABAM and Belgian telecom operator Belgacom unit Scarlet.

SABAM asked a Belgian court to order Scarlet to install a device to prevent its users from downloading copyrighted works. The court ruled in SABAM's favor and order Scarlet to install such a device. However, Scarlet then challenged the ruling, prompting the Belgian court to seek advice from the ECJ.

EU law precludes the imposition of an injunction by a national court which requires an internet service provider to install a filtering system with a view to preventing the illegal downloading of files, the ECJ said.

The filtering system would also be liable to infringe the fundamental rights of its (Scarlet's) customers, namely their right to protection of their personal data and their right to receive or impart information, the Luxembourg court said.

European consumer organization BEUC said the ruling should get authorities and companies thinking about a fairer way to provide easily accessible legal digital content for consumers.

The online marketplace has proven fertile ground, consumers spend billions of euro each year, said Monique Goyens, BEUC's director-general. Trying to criminalize individual consumers for file-sharing is just singing into the wind.

One lawyer said the verdict clarified who is liable for what.

It's a good ruling, it confirms basic principles about the allocation of responsibilities between ISPs and the ISP's users and ensures that ISPs will not be burdened by monitoring obligations, said Thomas Graf, a partner at law firm Cleary Gottlieb Steen & Hamilton.

Collecting societies collect royalty payments on behalf of authors, singers and performers. There are 24 such national organizations across the 27-country European Union.

The case is C-70/10, Scarlet Extended SA v. Societe Belge des auteurs, compositeurs et editeurs (SABAM).

(Additional reporting by Francesco Guarascio; Editing by Sebastian Moffett and Helen Massy-Beresford)