Most people tend unreflectively to assume that laws belong to legal systems. Most educated people, writes H. L. A. Hart, have the idea that the laws in England form some sort of system, and that in France or the United States or Soviet Russia and, indeed, in almost every part of the world which is thought of as a separate \u27country\u27 there are legal systems which are broadly similar in structure in spite of important differences. This includes for most people the assumption that laws differ from non-legal rules and principles. There are, for example, moral rules and principles, social customs, constitutions and regulations of voluntary associations, and so on, which are not laws. Many legal philosophers have tried to justify this co...