GENEVA -- A Swiss court has ordered an injunction halting the transfer of a former Credit Suisse employee's data to U.S. tax authorities, a lawyer involved in the case said on Tuesday.

The ruling highlights Switzerland's difficulties in balancing traditions of personal privacy against the United States' demands for data from roughly a dozen Swiss banks under formal investigation by U.S. prosecutors.

Those banks, including Zurich-based Credit Suisse, have been handing over information on their U.S. dealings for months now, part of efforts to avoid indictment and minimise fines for their role in helping wealthy Americans to evade taxes.

While these banks have clinched special Swiss government permission to deliver business data - but no client files - parliament failed last week to back a draft law covering the wider Swiss banking industry.

Douglas Hornung, a Geneva-based lawyer acting for the former Credit Suisse employee in the case, said the court ruling was made on June 21, confirming a preliminary decision in January.

While the court ruling is for one person's data, "it will set a precedent and could be repeated for other employees who had access to U.S. clients," Hornung, who also represents other former bankers, told Reuters on Tuesday.

Credit Suisse spokesman Marc Dosch declined to comment.

The Swiss banks under formal U.S. investigation have already made several transfers of data on employees linked to accounts of its U.S. customers, the last of which was in June.

Switzerland's biggest bank, UBS, was forced to pay a $780 million fine in 2009 and deliver the names of more than 4,000 clients to avoid indictment.

However, a U.S. indictment felled Wegelin & Co this year. Switzerland's oldest private bank paid a $58 million fine and closed its doors for good after pleading guilty to helping Americans to evade taxes through secret accounts.