William Lambarde played a pivotal role in the centralization of local government in late Elizabethan England. Although he has been frequently referenced in history as a legal scholar and antiquarian, his widely read manual for the justices of the peace, Eirenarcha: Or, of the Office of the Justices of the Peace (1582), demonstrates that his knowledge of the history of the common law enabled him to critically analyze the operations of local government in an effort to reform the way judicial administration was conducted by lay justices of the peace. This thesis investigates the work of Lambarde and his contribution to law reform in late Elizabethan England, particularly as revealed through the Eirenarcha. One of the chief reasons for the publication of Eirenarcha was to provide a solution to the inefficiencies and inaccuracies that persisted in the administration of law and justice by lay JPs. At a time when the law was neither rigidly applied nor uniformly understood, Lambarde provided a comprehensive and consistent source of legal knowledge that acted as a bridge between the central government and the JPs in the localities, proving Lambarde to be a central figure in the process of criminal justice reform in late Elizabethan England. Lambarde’s legal reforms put forth through his Eirenarcha ultimately brought about tangible changes to the commission and made a lasting impression on legal scholars well into the seventeenth century.