A top French appeals court on Wednesday upheld rogue trader Jerome Kerviel's three-year jail sentence over high-risk trading that cost Societe Generale bank nearly five billion euros.
But the court cancelled the 4.9 billion euros ($6.8 billion) that Kerviel was ordered to pay back, referring the issue of damages to another court for a fresh decision.
Kerviel's lawyer Patrice Spinosi had argued in February while appealing the conviction for breach of trust that Societe Generale had committed "wilful misconduct" and was aware of his client's high-risk trading.
The controversial trader spent 41 days in pre-trial detention in 2008, but was then released.
Kerviel is currently undertaking a protest walk from Rome to Paris, but can now technically be put behind bars at any time.
He was sentenced to three years in prison in October 2010 for breach of trust, forgery and entering false data for unauthorised deals that threatened to bankrupt the bank, one of the biggest in Europe.
Spinosi said Wednesday's decision to send the ruling on damages for judgement again would effectively amount to Societe Generale going on trial over the failure of its supervisory system.
"It is, at the very least, surprising that Jerome Kerviel is being sent to prison when the existence of significant failures by his employer and the consequences of these failures have just been recognised as a factor in the case," Spinosi added.
Another Kerviel lawyer, David Koubbi, termed the outcome of the hearing a "victory" for his client.
But Jean Veil, the lawyer for Societe Generale, said the 37-year-old Kerviel "has lost the case".
The controversial trader is on a 1,400-kilometre (870-mile) protest trek to highlight the "tyranny of the markets".
He had met with Pope Francis in the Vatican during the pontiff's weekly general audience on February 19 before starting his protest.
"This is great news, that's the only thing I will say," Kerviel said in a reaction to the ruling. "I will continue to walk."
He told RTL radio later: "It's the end of recreation for bankers and banks. It's the end of impunity. That's how I interpret it.
"I am quite surprised that they prefer to lock me up in prison rather that investigate the destruction of evidence," he added.
Kerviel and his lawyers had launched a high-profile campaign on social media before the case came before the appeal court.
His lawyer Koubbi said his client had received several offers of help and hospitality during his protest march.
When he was passing through Tuscany he was accorded a warm welcome by Marie-Christine Ferre, the widow of poet, composer and singer Leo Ferre.
"It gives us pleasure to help someone who is doing all this distance on foot just to save his skin," she was quoted as saying on the website of Kerviel's official support group.