In a landmark ruling, a French court has ordered Twitter to hand over details of users who posted racist and anti-semitic content.
Last October, the hashtag #UnBonJuif - a good Jew - started trending in the country, along with #SiMonFilsEstGay (if my son is gay), and #SiMaFilleRamèneUnNoir (if my daughter brings home a black guy).
Twitter removed the majority of the offending content from the site, but refused to hand over details of the groups making the posts, who were writing under pseudonyms.
Its refusal prompted the lawsuit from the Association of Jewish Students in France (UEJF) that led to today's ruling.
Twitter has been attempting to tread a fine line on censorship, saying only that it's prepared to remove posts in countries where they violate the law. In October last year, it put this policy into practice for the first time, blocking access to a neo-Nazi site in Germany.
However, it maintains that as its data is stored on servers in the US, it doesn't have to divulge the identity of users unless it's served with a court order in the US. It's been ordered to do so in the past, perhaps most notably in relation to Occupy protestors last year, on which occasion it resisted strongly.
The French decision puts this policy squarely under the spotlight. Twitter has said it's considering its options - although it'll need to think quickly. The company faces fines of $1,300 per day until it complies.
"This is a historic decision, that has delivered French justice today," says UEJF president Jonathan Hayoun. "It tells the victims of racism and antisemitism that they are not alone, and that the French law that defends them applies everywhere."