A collective-bargaining agreement between D and a union eliminated D's obligation to provide health benefits to subsequently retired employees, except as to then-current workers at least 50 years old. Ps who were then at least 40 and thus protected by the ADEA, but under 50 and so without promise of the benefits, claimed before the Equal Employment Opportunity Commission (EEOC) that the agreement violated the ADEA because it discriminated against them because of their age. The EEOC agreed. Negotiations failed, and Ps brought this action under the ADEA and state law. The District Court dismissed, calling the federal claim one of 'reverse age discrimination' upon which no court had ever granted relief under the ADEA. The Sixth Circuit reversed, reasoning that § 623(a)(1)'s prohibition of discrimination is so clear on its face that if Congress had meant to limit its coverage to protect only the older worker against the younger, it would have said so. D appealed, and the Supreme Court granted certiorari.