Still, Sun, 61, appears to have no shortage of resources at his disposal for the fight. From his new home base in Los Angeles, he has hired a top-flight law firm in Arent Fox, a personal assistant, a security firm and a team of lobbyists. He is driven to meetings by his assistant in a Mercedes-Benz sedan, which he said belongs to relatives he is staying with.

He declined to discuss the source of his funding, nor would he say what amount of his once-considerable assets he still holds.

In person, Sun comes off as surprisingly good-humored and quick to smile, laughing wryly when describing his jailing by Chinese authorities. That easygoing nature contrasts with his reputation for high-stakes gambles that built his fortune.

After working as a chemical analyst and then representative of a Japanese company in the northeastern Chinese province of Liaoning, Sun said he moved to Hong Kong in 1987 and started a host of companies in the hotel, real estate, food and textile industries. In 1996, he founded a Hong Kong energy company that later became GeoMaxima Energy Holdings, which became listed on the Hong Kong stock exchange through a reverse merger in 2001, according to news reports at the time.

GeoMaxima took on several oil and gas projects in China’s burgeoning energy industry and did not shy from riskier ventures. One of Sun’s biggest bets was a joint venture to build a 43-mile pipeline to the Tahe oil field in northwestern Xinjiang province, a project he said his competitors were wary of.

“They thought it was going to be a little one,” he said. “They didn’t want to invest to build the pipeline because they didn’t expect that much profit.”

The oil reserves there proved many times larger than initially thought, and the pipeline became lucrative, causing shares of GeoMaxima to skyrocket. The stock nearly tripled in eight months, giving the company a market capitalization exceeding $500 million by mid-2002.

Sun benefited from being part of an early wave of energy moguls and his big bets, but momentum quickly reversed. Sinopec, the largest company in China by revenue, bought out GeoMaxima’s partner in the Tahe pipeline and allegedly forced him out, refusing to pay oil transportation fees and building a second pipeline, in alleged violation of GeoMaxima’s 20-year exclusivity clause. By the end of 2002, his company’s shares had lost 90 percent of their peak value.