This chapter introduces the system of environmental regulation by building upon Ch. 4, which examined the sources of environmental law. In practice, environmental regulation involves more than the use of legal rules that forbid pollution and other forms of environmental harm. ‘Regulation’ is used to describe a wide range of different tools used in both legal and non-legal contexts—for example, it covers mandatory rules contained in environmental legislation, as well as non-binding environmental standards. The chapter outlines some of the reasons for regulating to protect the environment, before explaining how such regulation is introduced, applied, enforced, and reviewed. It examines the characteristics, strengths, and weaknesses of different approaches to standard-setting and the various instruments used to regulate potentially environmentally damaging activities. The chapter discusses several trends in modern environmental regulation, including the policy emphasis on deregulation and the use of information disclosure as a means of governing group or individual behaviour.