Patton Boggs has ended its role in long-running, multibillion environmental litigation against Chevron involving Ecuador with the announcement that it agreed to pay the oil giant $15 million and admitted regret for its role in the case.

In a settlement made public Wednesday, Patton Boggs said it would withdraw as counsel in any litigation against Chevron related to the Ecuadorian case, and Chevron agreed to release any claims against the firm.