British imperial magistrates applied distinct bodies of law in each colonial context. In contrast, a shared set of conventions for lawful government shaped administrative decision making throughout British world. This chapter highlights the importance of a broad and mutable mandate to keep peace for the exercise of power in Britain and its empire during the eighteenth century. It focuses primarily on two case studies. In December 1763, the so-called Paxton Boys massacred fourteen Conestoga Indians, whom the magistrates of Lancaster, Pennsylvania, protected in the town workhouse. Usually addressed as a violent turning point in colonial policy, this incident is indicative of a wider strategy of magisterial improvisation that shaped the development of imperial law. In South Asia, too, the writings of Magistrate Thomas Perry make clear, rhetoric and practices of peace allowed East India Company officials to impose British norms on Indian social and economic life. Perry and other British imperialists used what they saw as the failure of Mughal government to achieve peaceful society to argue for radical reforms to Indian courts, administrative structures, and patterns of landholding. A historiographical emphasis on legal pluralism has called attention to the varied and diverse bodies of law that divided European empires. This essay shifts focus to conventions and practices associated with legal peace. The project of maintaining order through law allowed local agents to improvise policies that constructed imperial sovereignty and jurisdiction through local practice.