Book excerpt: Justice among Nations tells the story of the rise of international law and how it has been formulated, debated, contested, and put into practice from ancient times to the present. Stephen Neff avoids technical jargon as he surveys doctrines from natural law to feminism, and practice from the Warring States of China to the international criminal courts of today. Ancient China produced the first rudimentary set of doctrines. But the cornerstone of international law was laid by the Romans, in the form of universal natural law. However, as medieval European states encountered non-Christian peoples from East Asia to the New World, new legal quandaries arose, and by the seventeenth century the first modern theories of international law were devised.New challenges in the nineteenth century encompassed nationalism, free trade, imperialism, international organizations, and arbitration. Innovative doctrines included liberalism, the nationality school, and solidarism. The twentieth century witnessed the League of Nations and a World Court, but also the rise of socialist and fascist states and the advent of the Cold War. Yet the collapse of the Soviet Union brought little respite. As Neff makes clear, further threats to the rule of law today come from environmental pressures, genocide, and terrorism.