Editors' Summary: In this first of a three-part series, the authors examine the history and general operation of the federal environmental crimes program. The authors first describe how an effective enforcement program emerged in the Justice Department and EPA despite various obstacles — including disagreements between and within the agencies about prosecutorial decisions — and how the program's history continues to influence decisions about what conduct EPA will investigate and what violations Justice will prosecute criminally. The authors also identify the major issues the program currently faces. The authors then discuss how the criminal enforcement program operates within a framework of civil rules and reporting obligations. They emphasize that the unique features of the system are that some instances of noncompliance will occur at even the best managed facilities and that virtually every act of noncompliance may be prosecuted criminally. The authors describe the case selection guidelines that EPA uses to decide which violations to investigate and refer to Justice, and that Justice uses to decide which cases to prosecute criminally. They also discuss the structure and enforceability of the permit system under major environmental laws, the crime of knowing endangerment, and the relationship between federal and state criminal enforcement efforts.