The FDA adopted a regulation without notice or comment informing food producers of the maximum amount of unavoidable contaminants that it would permit. During court action to enforce a determination of condemnation of interstate food shipments as adulterated, the FDA has to prove that the foods were adulterated. D objected to the use of the FDA regulations to determine what was adulterated. FDA defended on the grounds that those regulations were exempted under section 533 as interpretative rules and general statements of policy. FDA claimed that action levels represented nothing more than nonbinding statements of agency enforcement policy. D argued that the action levels restrict enforcement discretion to such a degree that they are legislative rules. On the first time on appeal, the court concluded that the FDC Act, by stating that FDA 'shall promulgate regulations,' 21 U.S.C. § 346, required that FDA issue formal regulations or 'tolerances,' rather than informal action levels. The Supreme Court reversed that decision, holding that the FDC Act was not so clear as to preclude FDA's interpretation of the statute under which the agency could lawfully proceed by way of action levels. The Court did not reach the APA or blending issues and remanded the case for 'further proceedings consistent with [its] opinion.' The appeals court now addresses the issues of whether the action level violates the Administrative Procedure Act because it constitutes a legislative rule issued without the requisite notice-and-comment procedures, see 5 U.S.C. § 553; and if D's decision to permit adulterated corn to be blended with unadulterated corn to bring the total contamination within the action level violated the FDC Act.