New York Times:

After oil prices surged past $100 a barrel in 2008, suspicions that traders had manipulated the market led to Congressional hearings and regulatory investigations. But they produced no solid cases in the record run-up in gasoline prices.
But on Tuesday, federal commodities regulators filed a civil lawsuit against two obscure traders in Australia and California and three American and international firms.
The suit says that in early 2008 they tried to hoard nearly two-thirds of the available supply of a crucial American market for crude oil, then abruptly dumped it and improperly pocketed $50 million.
The regulators from the Commodity Futures Trading Commission would not say whether the agency was conducting any other investigations into oil speculation. With oil prices climbing again this year, President Obama has asked Attorney General Eric H. Holder Jr. to set up a working group to look into fraud in oil and gas markets and “safeguard against unlawful consumer harm.”
In the case filed Tuesday, the defendants — James T. Dyer of Australia, Nicholas J. Wildgoose of Rancho Santa Fe, Calif., and three related companies, Parnon Energy of California, Arcadia Petroleum of Britain and Arcadia Energy, a Swiss company — have told regulators they deny they manipulated the market.
If the United States proves the claims, the defendants may give up $50 million in profits that were believed to be made as a result of the manipulation and also pay a penalty of up to $150 million.
The commodities agency says the case involves a complex scheme that relied on the close relationship between physical oil prices and the prices of financial futures, which move in parallel.
In a matter of a few weeks in January 2008, the defendants built up large positions in the oil futures market on exchanges in New York and London, according to the suit, filed in the Federal Court in the Southern District of New York.
At the same time, they bought millions of barrels of physical crude oil at Cushing, Okla., one of the main delivery sites for West Texas Intermediate, the benchmark for American oil, the suit says. They bought the oil even though they had no commercial need for it, giving the market the impression of a shortage, the complaint says.
At one point they had such a dominant position that they owned about 4.6 million barrels of crude oil, estimating that this represented two-thirds of the seven million barrels of excess oil then available at Cushing, according to lawsuits.
This type of oil is also the main driver of prices of the futures contracts, and their actions caused futures prices to rise, the authorities say. “They wanted to lull market participants into believing that supply would remain tight,” the agency said. “They knew that as long as the market believed that supply was tight and getting even tighter, there would be upward pressure on the prices of W.T.I. for February delivery relative to March delivery, which was their goal.”
The traders in mid-January cashed out their futures position, and then a few days later began to bet on a decline in oil futures, with Mr. Wildgoose remarking in an e-mail about the “inevitable puking” of their position on an unsuspecting market, the federal lawsuit says.
In one day, Jan. 25, they then dumped most of their holdings of West Texas Intermediate oil, and profited by the drop in futures.
The traders repeated the buying and selling in March 2008, and were preparing to do it again in April but stopped when investigators contacted them for information, the suit says.
Between January and April, average gas prices rose roughly to $3.50 a gallon, from $3. It was not until later in 2008, after the defendants had ceased their reported actions, that oil prices soared higher — reaching $145 that July. By the end of the year, prices had fallen to about $44. The Texas oil is now around $100.
Many other factors were at work, including tight oil supplies in the Middle East and fears that a growing global economy would consume more oil. Yet the enforcement action by the commodities regulator was the first credible evidence that a small group of traders also played a role in manipulating prices.

The rest here.

One thing they’ll have to examine here is the amount of credit extended to these trading firms and the margin requirement on said loans. If this trading is indeed illegal, the banks might be held accountable, too, for helping to facilitate the transactions.