A Swiss court on Wednesday temporarily banned Credit Suisse, the country's second biggest bank, from handing confidential information about a bank employee to US tax authorities.
The emergency injunction by a Geneva court was a twist to the acrimonious issue of tax evasion involving Swiss banks. Eleven banks are being probed by US authorities as part of an investigation into tax dodging.
The lawyer who secured the ban on behalf of his client, a Credit Suisse employee, hailed it as a "victory" for "betrayed staff" which he said sent a message to other banks that such action might not be legal.
"The court's decision could be good news (for employees)," Geneva lawyer Alec Reymond told Radio Television Suisse.
He added that the injunction, albeit temporary, represented "a strong warning to all banks" which planned to send workers' details to the US.
Reymond approached the Geneva court on Tuesday to stop Credit Suisse sending a second round of documents to the US this month.
The bank had already sent information to the US about his client, the lawyer said, arguing before a judge that the release of any further details would damage his client's interests irreparably.
The fact that Credit Suisse had already sent "innumerable" documents to the US rendered the victory of the court's ruling "a little bitter and a little late", Reymond said.
While the injunction is temporary, until both parties can be heard in court, Reymond described it as "a rejection of all banks" which thought they were "beyond the reach of all the usual processes" and could simply "offload" data concerning employees and ex-employees to a foreign country.
The other banks targeted by the US are Julius Baer, Wegelin, Banque cantonale de Zurich, la Banque cantonale de Bale, Neue Zuercher Bank, HSBC, LLB, in addition to the Israeli banks Leumi, Hapoalim and Mizrahi.
Swiss President Evelyne Widmer-Schlumpf has announced that she hopes to resolve differences with Washington on the tax issue this year.