Section 109 (a)(3), 30 U.S.C. § 819 (a)(3), is part of the enforcement scheme of the Federal Coal Mine Health and Safety Act of 1969. The Act prescribes health and safety standards for the protection of coal miners. It requires coal mine operators and miners to comply with the standards. D is to conduct continuing surveillance of mines by inspectors. Among the purposes of the inspections are finding imminently dangerous conditions and violations of mandatory health or safety standards. If an imminent danger is found, the inspector is required to issue a withdrawal order compelling the mine operator to withdraw all persons from the danger area. If a violation of a mandatory standard is found that is not imminently dangerous, the inspector issues a notice to the operator fixing a reasonable time for its abatement. If the violation is not abated and the time for abatement is not extended, the inspector then issues a withdrawal order. Withdrawal orders are also issued for any 'unwarrantable failure' of mine operators to comply with the standards. The notices and orders issued contain a detailed description of the dangerous conditions or violations and their locations. The notices must be in writing and given promptly to the mine operators. The Act requires D to assess and collect civil penalties. Section 109 (a)(3), authorizes D to assess a civil penalty only after the operator charged with a violation 'has been given an opportunity for a public hearing and the Secretary has determined, by decision incorporating his findings of fact therein, that a violation did occur, and the amount of the penalty which is warranted….' Hearings must be of record and subject to provisions of the Administrative Procedure Act, 5 U.S.C. § 554. Ps are concerned with the assessment of penalties under §109 (a)(3). Regulations provide that assessment officers assess a penalty based on a notice of violation issued by mine inspectors and a penalty schedule graduated according to the seriousness of the violation. The regulations provide that Ps are to be advised when they receive original or reissued proposed orders that they have 15 working days from the receipt of the order to 'protest the proposed assessment, either partly or in its entirety.' If an operator fails to make a timely protest and request adjudication, he is 'deemed to have waived his right of protest including his right of formal adjudication and opportunity for hearing….' The proposed assessment order then becomes the 'final assessment order of the Secretary.' If an operator makes a timely request for a formal hearing, the assessment officer is required to forward the matter to the Officer of the Solicitor, Department of the Interior. A petition to assess a penalty can then be filed by the Solicitor with the Department's Office of Hearings and Appeals. The petition is served on P who then has an opportunity to answer and secure a public hearing. Whether or not P requests formal adjudication, he may obtain de novo judicial review of the amount of the penalty by refusing to pay it and awaiting D's enforcement action in the district court. Ps brought suit against D to enjoin the use of these regulations. The court granted P's motion for summary judgment, holding that the summary procedures were not authorized by §109 (a) of the Act. The Court of Appeals for the District of Columbia Circuit reversed. It held that absent a request for a hearing, D is entitled to conclude that the operator does not dispute the proposed order, including the factual basis of the violation. The Supreme Court granted certiorari.