The Contract Disputes Act establishes rules governing disputes arising out of certain Government contracts. The statute provides that these disputes first be submitted to an agency's contracting officer. A Government contractor dissatisfied with the contracting officer's decision may seek review either from the United States Court of Federal Claims or from an administrative board in the agency. Either decision may then be appealed to the United States Court of Appeals for the Federal Circuit. In 1998 Congress enacted the National Parks Omnibus Management Act of 1998 establishing a new and comprehensive concession management program for national parks. The Act authorizes the Secretary of the Interior to enact regulations implementing the Act's provisions. That authority was delegated to the National Park Service. NPS promptly began a rulemaking proceeding to implement the Act. After notice and comment, final regulations were issued in April 2000. A concession contract (or contract) means a binding written agreement between the Director and a concessioner . . . . Concession contracts are not contracts within the meaning of 41 U.S.C. 601 et seq. (the Contract Disputes Act), and are not service or procurement contracts within the meaning of statutes, regulations or policies that apply only to federal service contracts or other types of federal procurement actions. § 51.3. Beginning in 1989, the Department of Interior's Board of Contract Appeals ruled that NPS concession contracts were subject to the CDA and subsequent attempts by NPS to convince the IBCA otherwise proved unavailing. National Park Hospitality Ass'n (P) challenged the validity of § 51.3. The District Court upheld the regulation, applying the deference principle of Chevron U.S.A. Inc. v. Natural Resources Defense Council, Inc. The court concluded that the CDA is ambiguous on whether it applies to concession contracts and found NPS' interpretation of the CDA reasonable. The Court of Appeals affirmed. It simply found that NPS' reading of the CDA consistent with both the CDA and the 1998 Act. The Supreme Court granted certiorari to consider whether the CDA applies to contracts between NPS and concessioners in the national parks.