European national courts in several countries have ordered Internet providers to block certain websites or to filter all traffic passing across their networks in order to reduce copyright infringement. But a new legal opinion (PDF) from one of Europe's top lawyers says that such orders are not allowed, and that they violate various European “fundamental rights.”

Judges from countries like Belgium and the Netherlands have issued several blocking or filtering requirements over the last several years. In 2007, for instance, the Belgian ISP Scarlet was ordered to halt copyright infringement on its network through traffic filtering and site blocking. That case has escalated to Europe's highest court, the Court of Justice of the European Union, where today an Advocate General found the Belgian order inappropriate.

The Scarlet order violated several items in Europe's Charter of Fundamental Rights, including the rights to private communication, protection of personal data, and freedom of information. Such rights can be abridged, but not on an ad hoc basis by judges ruling in particular cases. Advocate General Pedro Cruz Villalón found that Internet restrictions are only acceptable if they "were adopted on a national legal basis which was accessible, clear, and predictable.”

In other words, the legislature has to act first. It did so in the Scarlet case; Belgium passed a law granting judges some leeway in holding Internet providers more responsible for the behavior of their users. But the Belgian legislation did not provide a specific proposal, it did not apply it to everyone, and nowhere did it say that ISPs would bear all the costs.

The Advocate General concludes that the Court of Justice should rule in favor of Scarlet, which has objected to the blocking and filtering provisions for years. On the basis of current Belgian law, no Belgian court should require an ISP to to unlimited filtering and blocking, entirely at the ISP's expense, and wholly as a "preventative" measure.

The opinion is not binding on the Court of Justice judges deciding the case, but it is commonly followed. If adopted, the ruling would make many rightsholder threats to haul ISPs into court (as we saw in Ireland) fairly toothless until rightsholders can push some passable legislation through their national parliaments.

Even this legislation would have limits, though. Today's opinion finds that indiscriminate blocking and filtering which is "systematic," "universal," and cannot be challenged lacks "adequate safeguards" for users' fundamental rights.

The ruling thrilled people like Swedish Pirate Party leader Rick Falkvinge. "It has been the modus operandi of the copyright industry to threaten ISPs with 'block to our wishes or we’ll take you to court,'" he wrote. "This has been their standard operating procedure for the past couple of years, in order to establish enough precedents to get them written into law. Today’s verdict, or potential verdict, gives those ISPs the power to say 'go play on the highway, parasites, we have a paper from the highest possible court saying no court can force us to do that. We care more about our customers than about obsolete irrelevants.'"