Experts have reported back to a French judge set to make a landmark court decision on the responsibilities of portals for content on their servers - and their verdict is inconclusive.

A three-man panel including French expert Francois Wallon, US internet founder Vint Cerf and open source expert Ben Lauris testified that it would be possible for portals to detect the 70 per cent of French surfers who currently use an identifiable ISP in France, but not all French surfers.

The case has arisen because Yahoo was accused of violating French law on the sale of anti-Semitic Nazi paraphernalia in May following a lawsuit filed by the International League Against Racism and Anti-Semitism (Licra), and the Union of French Jewish Students.

At that time, the judge ordered the company to examine ways to "render it impossible" for French citizens to access the Nazi material. Yahoo said it was impossible to do so, so Paris Tribunal Judge Jean-Jacques Gomez called in independent experts to examine the technical feasibility of denying French surfers access to the disputed web pages.

"We're using a technology used by Yahoo US to display web ads to French users," Wallon told vnunet.fr. "For that purpose, they're using IP address geographic data, which works fine for French ISPs but not for AOL for instance."

Yahoo has until 16 November to respond to the findings, with a decision expected on 20 November, according to a report on vnunet.fr.

Yesterday's testimony that the portal can at least partially prevent access to the more than 1000 such examples of anti-Semitic Nazi paraphernalia that can be found on the auction pages of Yahoo's US website could cost the portal dear.

Licra has called upon Judge Gomez to fine Yahoo up to 200,000 euros (£120,000) for every day it allows access to the banned material for three months. A Licra spokesman welcomed the report and blasted Yahoo as hypocrites.

"They say they want to co-operate, but they're not willing to," said Marc Knobel, committee director at Licra. "When dealing with alcohol or betting, which is forbidden in various [US] states, they easily manage to filter it. Yahoo's behaviour is hypocritical. Under freedom of speech, they display on their website objects from barbaric times."

The ruling is being watched, because it could set a precedent on international jurisdiction, an issue which Yahoo previously said "should be discussed and addressed by representatives of governments and the internet industry around the world".