Hollywood actor-activist George Clooney has taken aim at the prominent D.C. lobbying firm Squire Patton Boggs in a searing new op-ed for Time, denouncing the firm for agreeing to represent the Sudanese government in its efforts to lift long-standing U.S. sanctions against the country.

“The firm will be paid $40,000 a month by a government that’s on the U.S. state sponsors of terror list, with a head of state, Omar al-Bashir, wanted for genocide by the International Criminal Court,” wrote Clooney and co-author John Prendergast, a fellow activist and former Clinton administration official.

Clooney and Prendergast — co-founders of the Sentry, an international advocacy group that investigates the funding and profiting from genocide in Africa — specifically called out three of the firm’s most high-profile executives: former House speaker John A. Boehner and former senators Trent Lott and John Breaux.

“Either they don’t know that their firm is taking $40,000 a month from the government of Sudan, or they don’t know what this regime has done,” the activists wrote. “It’s also possible they don’t know that the government of Sudan continues to use starvation as a weapon of war on its own people, still funds militias that murder its own innocent civilians, and continues to loot the country of its natural resources and funnel the wealth of Sudan into the hands of regime leaders through massive corruption.”

Clooney has long been an outspoken advocate for war-ravaged Sudan: In 2012, the A-list star made headlines after he was arrested as he protested outside the Sudanese Embassy in Washington. He has testified before Congress about the violence and humanitarian crisis along the Sudan-South Sudan border, and met personally with President Barack Obama to discuss the plight of the Sudanese.

A spokesman for Squire Patton Boggs didn’t comment on whether Boehner, Lott and Breaux were aware of or involved in the firm’s arrangement with the Sudanese government. In a statement, the firm cited “many observers” who maintain that engaging with Sudan, rather than isolating its government, is a better way to improve humanitarian aid and reduce conflict in the region.

“While we recognize and respect that others may have different views, our firm will be working with Sudan as it seeks to continue to meet the expectations of our government,” the firm said in its statement.