In Amos Treat & Co. v. Securities and Exchange Commission, 306 F.2d 260 (D.C.Cir.1962), the court considered a challenge to a former division director of the SEC participating after his appointment as a commissioner in a case in which he had prior involvement. The dual role of the commissioner was challenged both under the Administrative Procedure Act (APA) and on due process grounds. The decision was based on due process considerations. Id. at 267.