Quito, May 12 (RHC)-- A major Washington D.C. law firm has dropped out of a lawsuit against the oil giant Chevron for pollution in Ecuador’s Amazon rain forest.

Patton Boggs had helped represent a group of indigenous plaintiffs who won a landmark $9 billion judgment in 2011 for widespread contamination resulting from toxic dumping by Texaco, which Chevron later bought.

Chevron turned around and sued the victims and their U.S. attorney, accusing them of bribing the judge in the case and presenting fraudulent evidence. Chevron won the lawsuit in March, with a federal judge barring collection of their $9 billion judgment in the United States.

Patton Boggs withdrew from the case after Chevron threatened legal action over the firm’s role in the Amazonians’ case. Patton Boggs has also agreed to pay Chevron $15 million.

Bloomberg BusinessWeek reports the firm’s retreat "is highly unusual and possibly unprecedented." It could be linked to Patton Boggs’ current effort to merge with a larger firm amid a series of financial woes.