BEIJING - A court ruling that stripped a Chinese investor of millions of yuan gained six years ago from transactions of paper gold with the world's largest bank has triggered a fresh wave of public criticism.

Song Ronggui, whose gains of 21 million yuan ($3.33 million) were retrieved by the Industrial and Commercial Bank of China (ICBC), the world's biggest lender by market value, said it would challenge the investor's appeal to the Supreme People's Court.

Song said he had lodged an appeal after the Higher People's Court of Shandong province recently issued a final sentence that favored the bank's cancellations of 126 transactions of cash-settled and non-delivery contracts.

"I'm very upset (at the ruling)," Song said, vowing to continue the legal proceedings at the Supreme People's Court.

In its final judgement, the Higher People's Court of Shandong supported the move by the ICBC branch in the provincial capital of Jinan to call off 126 paper gold transactions between June 29 and July 8, 2006.

On the gold exchange platform provided by the ICBC, Song and his investment partner Fan Wenda adopted a stop-loss order strategy to arbitrage on the spread of the bid and ask prices of gold through phone banking.

According to the rules on the stop-loss order, investors can buy or sell stock through phone or the Internet once the price of the underlying stock reaches a specified price, known as the stop price. When the stop price is reached, the stop order becomes a market order, meaning the trade will definitely be executed, but not necessarily at or near the stop price, particularly when the order is paced into a fast-changing market, or if there is insufficient liquidity available relative to the size of the order.

In their arbitrage dealings, Song and Fan placed most of their bid orders at 145 yuan per gram through phone when the gold price was 160 yuan per gram and resold them at the market price, an operation strategy Song argued was in line with the trading system's floating limit of 20 percent on either side of the market price.

However, the ICBC has accused their operations as "evidently hostile" and called their gains from the transactions "unjust enrichment," stating that those transactions could be revoked on the premise of "system malfunction."

To Song's fury, the ICBC branch transferred, without notice, from his and Fan's bank accounts the 21 million yuan of profits they earned through the transactions in late July 2006 even before any binding legal ruling was announced.

"Such move (by the bank) is sort of pirating," said Sun Qilun, a lawyer representing Song. "It's unconvincing for the bank to ask for the revocation of those transactions on the ground of system malfunction."

On China's Twitter-like websites, the case has become one of the heated topics for microbloggers, who have largely sympathized with Song.

"Those who make a mistake should pay the price on their own. The system malfunction has nothing to do with customers," read one post.

"In China, the banks are always right," said Chen Xing, an Internet commentator.

"The court ruling protects the interests of the monopoly industry and ruins market rules," read another post.

Internet users compared the case with an ATM malfunction of the HSBC in Hampshire, Britain, last month.

About 200 residents cashed in after a HSBC ATM began paying out double in May. But the bank said it would not be asking any customers to return the money as it was not the customers' fault.

"The machine was mis-dispensing and we won't be requesting the funds back. It is certainly not the liability of the customers," according to a HSBC spokesman.

Chinese banks, however, have long been criticized for making fat profits with numbers charges and fees while treating their customers without respect.

Chinese commercial banks posted an increase of 36.34 percent year-on-year in net profits to 1.04 trillion yuan in 2011 while the world's second-largest economy is slowing.

Song said he was not optimistic that the verdict would be overturned as the Supreme People's Court in 2008 upheld a five-year jail term meted out by a local court in southern Guangdong province to a young man who was found guilty of "illegally" withdrawing 175,000 yuan from an ATM machine.

In that final ruling at the Supreme People's Court, Xu Ting was jailed for five years after he took 175,000 yuan from a faulty ATM machine in Guangdong in April 2006.

The ATM only deducted 1 yuan from Xu's account for each 1,000 yuan that he had withdrawn.