A Swiss court has ruled that Credit Suisse's decision to provide US tax authorities with information on an employee was illegal, according to the ruling made public Monday.
In April 2012, the Swiss government gave 11 Swiss banks the go-ahead to accommodate a US tax evasion probe and hand over the names of thousands of their employees and consultants working with American clients.
Fearful of harsh US penalties and prosecution, the banks then met Washington's demands, handing over personal information about numerous staff members, and reportedly also making personal documents, emails and details of telephone calls available.
But in a ruling reached on May 28 but made public Monday, a Geneva court found in favour of a former Credit Suisse employee, who had challenged Switzerland's second largest bank over the information about her given to US authorities in 2012.
The woman, who was not named, had not been informed at the time that information concerning her was being shared -- something that ran counter to Switzerland's long cherished bank secrecy practices, which are currently increasingly being dismantled under international pressure.
In the first Swiss court ruling on the controversial practice, the Geneva court noted "the unlawfulness of Credit Suisse's communication to US authorities, outside an international process of mutual assistance, documents containing data" on the former employee, making it possible to identify her.
The court found that the woman, who was not named, "can legitimately consider that she will be at risk if she travels to the United States," and ruled that this impacted her "freedom of movement, (and) constitutes a deprivation of (her) personal liberty".
Lawyer Douglas Hornung, representing the former employee, described the ruling as "an important first-step victory."
It could have implications for the some 400 other current and former employees of Swiss banks who his law firm represents in similar cases.
Credit Suisse, which as a result of the US probes was slapped with a $2.8-billion fine last year after pleading guilty to having helped rich Americans evade taxes, said it had taken note of the Geneva court ruling.
"We plan to appeal," spokesman Jean-Paul Darbellay wrote in a statement sent to AFP.
"The court has decided on an individual case and has not determined that the cooperation under the authorisation by the Swiss Federal Council is generally illegal," he said.