John Rawls is considered to be one of the most important political thinkers of the 20th century. In his last original work, The Law of Peoples, he included his comprehensive theory of international relations. Following the idea outlined in his former work, A Theory of the State, author divides participants of international affairs into five types of domestic societies: “reasonable liberal peoples”, “decent peoples” (to liberal and decent peoples Rawls refers together as “well-organized peoples”), “outlaw states”, “societies burdened by unfavourable conditions” and “benevolent absolutisms”. The Author intentionally uses the term “peoples”, in order to clearly distinguish “the law of nations” from “the law of peoples”. He claims that in international politics traditionally conceived “nations” or “states” are moved mainly by their own particular interests — reason of state. Unlike states, well-organized peoples are just, or decent; they have a certain moral character, and in international relations reasons for their conduct accord with corresponding principles. Furthermore, governments of states consider their right to go to war to be undeniable, and derive this right from positive international law. Yet Rawls claims that ius ad bellum is not an innate right of every actor of international relations: only well-organized peoples are entitled to it, provided the reason for the use of force is the necessity to defend themselves from the aggression of an outlaw state. The distinction between non-aggressive well-ordered peoples and aggressive outlaw states is a basic assumption for Rawls’ further reflections on possible ways of coexistence of well-ordered peoples with peoples that fail to meet the criteria of “liberalism” or “decency”, leading to the main question: how to bring eventually all societies to honour the law of peoples and to become full members of the society of well-ordered peoples.