The Federal Coal Mine Health and Safety Act set forth health and safety standards for the protection of coal miners. Under the Act, the Secretary of the Interior (defendant) assessed and collected civil penalties against mine operators who violated provisions of the Act. Pursuant to the Secretary’s regulations, assessment officers assessed penalties based on notices of violations issued by mine inspectors. Upon receiving a proposed assessment, mine operators had fifteen working days to protest the proposed assessment and request adjudication. If the mine operator failed to protest, the Act deemed the mine operator to have waived the right to formal adjudication and the proposed assessment became the Secretary’s final assessment. A group of mine operators (plaintiffs) challenged the Secretary’s regulations, arguing the Act required the Secretary to make a formal decision incorporating findings of fact before assessing a penalty, regardless of whether a hearing was requested.