He'll have to pay a fine in the millions of dollars, the nation's high court ruled.
Here is the latest, from the Associated Press:
French Court Uphold Soros Conviction
The highest court in France on Wednesday rejected a bid by George Soros, the billionaire investor, to overturn a conviction for insider trading in a case dating back nearly 20 years, leaving the first blemish on his five-decade investing career.
The panel, the Cour de Cassation, upheld the conviction of Soros, 75, an American citizen, for buying and selling Société Générale shares in 1988 after receiving information about a planned corporate raid on the bank.
Ron Soffer, his lawyer, said Soros planned to take the case to the European Court of Human Rights, saying that the length of the proceedings had prevented his client from having a fair trial.
"The investigation started in 1989," he said. "The appeals trial occurred in 2004. How can you call witnesses and ask them about what happened in 1988?" The French stock market regulatory authority investigated the matter separately and concluded that Soros had not violated the law or any ethical rules, Soffer said.
The French authorities have not yet determined what fine Soros will pay.
In a March 2005 ruling, a French appeals court confirmed a fine of €2.2 million, or $2.8 million, set by a lower court for the illegal purchase of 95,000 shares in Société Générale. The Cour de Cassation ruled that the fine would be adjusted to reflect Soros' profits, and it ordered the case returned to the appeals court to clarify the amount.
Soros, a Hungarian-born businessman, has acknowledged that he was told about a Paris financier's plans to take over Société Générale in late 1988 and began independently acquiring shares in the bank just days later.
But he denied that knowledge of the raid had amounted to insider information or influenced his transactions, which he said were part of a broader, documented strategy of investing in newly privatized French companies. Soros' lawyer said he had cooperated in the case from the beginning.
A spokesman for Soros, Michael Vachon, called the decision "an absurd miscarriage of justice" and said Soros was confident he would be cleared by the European court.
"As he has from the beginning, George Soros maintains that he engaged in no illegal or unethical conduct," Vachon said in a statement.
Soros, who emigrated to the United States in 1956 and set up Soros Fund Management 17 years later, has billions of dollars under management in his Quantum Fund.
He remains the only person convicted in the Société Générale affair. Two others, Samir Traboulsi and Jean- Charles Naouri, were acquitted.
At an appeals hearing in 2005, Soros told the court his insider trading conviction had been a "gift to my enemies" in the United States and elsewhere. "My reputation is at stake," he said.
Soros has often drawn criticism for speculating heavily on the collapse of fragile currencies. In 2004 he also angered many conservatives in the United States by pumping millions of dollars into election campaigns to try to unseat President George W. Bush.