Calyon lost $350M on unauthorized credit bets — discovered after Labor Day weekend

Calyon was the corporate and investment banking arm of Crédit Agricole, one of Europe's largest banks. Its New York proprietary trading desk specialized in credit derivatives.

In October 2007, Calyon announced a $347.5 million charge from unauthorized trading by its New York prop desk. A 26-year-old trader, Richard 'Chip' Bierbaum, had built large positions in credit market indices above his authorized limit in late August. The trades were executed on the bank's own balance sheet without the required approvals.

Risk managers only discovered the unauthorized position days later when they returned after the Labor Day weekend. Bierbaum was immediately fired. He publicly rejected the 'rogue trader' label, claiming his positions were reported daily and that superiors considered him a 'golden child.'

The loss sharply reduced Calyon's third-quarter profit. Trading limit alerts and security controls were immediately strengthened. The incident raised questions about whether Calyon's risk management systems met MiFID regulatory requirements, with ILOG publicly criticizing the delay in detection.