Abstract: East Asia is still politically and diplomatically divided while increasingly becoming integrated economically. East Asian states, excluding Japan, share a common experience in that they were deprived of their sovereignty, in part or as a whole, by Western or Japanese colonial powers. The experience still defines current international relations among East Asian countries, raising the issue of justice in international law. International lawyers, however, have been, in general, reluctant to talk about justice in international law. Before the 19th century, international law was dominated by naturalism or natural law doctrine. The international community was composed of European states, excluding non‐Christian and non‐European states. From the early 19th century to the end of World War II, international law was dominated by these states’ will. International law had developed various principles to facilitate Western powers’ colonial occupations and in the 19th century, international law was a tool for Western colonialism and imperialism. After World War II, international law almost abolished the divide between European and non‐European, Christian and non‐Christian, and civilized and non‐civilized states. Colonization is not allowed anymore and many parts of the world that had belonged to former colonies in Africa and Asia became independent states. Further, human rights are no longer considered internal affairs of a state. Asia met with Western powers when positivism was prevalent. The relationship between China and neighboring countries, such as Korea, Burma, Thailand, Vietnam, and the Ryukyu Islands, had been maintained by a tributary system until the mid‐19th century. The China‐centered tributary system, maintained for centuries in East Asia, was replaced, however, by a capitulation system from the mid‐19th century. East Asian states concluded many unequal treaties with Western powers and East Asian people might have been confused by the paradox of the principle of equality among sovereign states and the unequal nature of the treaties that were forced against them. Efforts to recover sovereignty and to decolonize after World War II in East Asia seem to be far from satisfactory. Japan has never recognized its legal responsibility from colonialism. Even with the conclusion of the San Francisco Peace Treaty, many territorial issues still remain unresolved in East Asia. The Peace Treaty did not settle various colonialism‐related claims between Japan and neighboring countries, failing to render an effective remedy for past human rights violations. Thomas Franck argues that a rule’s legitimacy enhances its compliance. Steven R. Ratner argues that international law rules would be deemed just if they were to (i) advance international peace, and (ii) respect basic human rights. If the international community is really a legal community where states are bound by rights and duties, it should be naturally based on justice. The legacy of past colonialism in East Asia that might hinder global peace and respect for human rights should be addressed in the near future.