This article is concerned with the concept of public policy in English arbitration law and eventually the concept of international public policy. As the analysis shows, public policy operates in the form of legal rules that are ascertained from a careful analysis of the decisions of English courts. Although the underpinning justifications and public policy tests used by English courts are typically broad, the rules of public policy are mostly clear and well defined. This narrowly defined concept of public policy in English law can be contrasted with the concept of transnational public policy that currently prevails in international arbitration, which, as the article argues, is ill defined and unwarranted, being understood as a set of general principles of morality.