A Belgian court fined Internet search engine Yahoo €55,000 ($69,300) on Monday for failing to hand over personal account information of users suspected of committing fraud online.
Daily fines of €10,000 ($12,590) will be added onto the fine if Yahoo continues to not comply with the courts orders.
In an enquiry into fraud carried out by a gang of alleged internet cons who used pseudonyms in Yahoo email addresses, the prosecutor called on Yahoo to provide their true identities.
California-based Yahoo refused, arguing that it was a US company and therefore such information would have to be requested through US authorities, not from Belgium.
We strongly disagree with the court's ruling, Yahoo said in a statement.
The United States and Belgium have a formal international treaty which the prosecutor should have followed to properly seek information from a US company.
Meanwhile, Belgian investigators claim Yahoo should hand over the data since the company also operates its services in Belgium. The European country's authorities also stressed that it never had any such problems with Yahoo's rivals, Google and Microsoft.
Yahoo was denigrated by US lawmakers in 2007 for providing the Chinese government with email and other information that led to the imprisonment of two men that had advocated online for democracy in the Communist country.
Yahoo then went on to settle the filed by the Chinese men and their families in US federal court.