David and Charles Koch have thrown another punch in their ongoing fight against The Cato Institute, the Washington, D.C.-based libertarian think tank that they helped found. On Monday, the billionaire brothers filed a second suit in state court in Kansas against Cato, challenging its appointment of four new board members. 

Also on Monday, Theodore Olson—the Gibson Dunn & Crutcher partner who’s both a Cato board member and Koch Industries’ outside counsel— filed an affidavit in support of the suit. And while Stinson Morrison, which filed the Kochs’ first suit against Cato, is also working on the second suit, the brothers have also retained Williams & Connolly.