Editors' Summary: Section 304 of the Clean Air Act enacted in 1970 was the first provision expressly empowering citizens to act as private attorneys general to enforce a federal statute. Every federal environmental statute enacted since 1970, except FIFRA, has included a citizen suit provision, and each provision has been modeled on §304. In Part I of this three-part series, Mr. Miller discusses the origin and legislative history of citizen suits and explains the similarities and differences among the various provisions. He describes who may and may not bring suit and who may be sued. Mr. Miller also discusses the types of violations that are subject to citizen suit actions and the penalties authorized under the different statutes. In addition, he explains the significance of the savings clause provisions in relation to citizen suit provisions and discusses, in particular, whether these clauses preserve a federal common law of nuisance, an implied private right of action, or jurisdiction under the general jurisdictional statutes.