NLRB v. Bell Aerospace: The NLRA did not initially cover managerial employees (as interpreted by the NLRB), but the NLRB changed its policy and chose to cover managerial employees. The NLRB chose to make the change through adjudication rather than rulemaking. Bell Aerospace argued the NLRB couldn't do so because it had relied on the NLRB's prior interpretation. - Rule: Where reliance interests are so substantial that applying the new policy would harm the industry, an agency must use prospective rulemaking. o Still unclear whether prospective adjudication is permissible to relieve the problem.