History of public international law

The history of public international law examines the evolution and development of public international law in both state practice and conceptual understanding. Modern international law developed out of Renaissance Europe and is strongly entwined with the development of western political organisation at that time. The development of European notions of sovereignty and nation states would necessitate the development of methods for interstate relations and standards of behaviour, and these would lay the foundations of what would become international law. However, while the origins of the modern system of international law can be traced back 400 years, the development of the concepts and practises that would underpin that system can be traced back to ancient historical politics and relationships thousands of years old. Important concepts are derived from the practice between Greek city-states and the Roman law concept of ius gentium (which regulated contacts between Roman citizens and non-Roman people). These principles were not universal however. In East Asia, political theory was based not on the equality of states, but rather the cosmological supremacy of the Emperor of China.

Basic concepts of international law such as treaties can be traced back thousands of years. Early examples of treaties include around 2100BC an agreement between the rulers of the city-states of Lagash and Umma in Mesopotamia, inscribed on a stone block, setting a proscribed boundary between their two states. Around 1000BC, an agreement was signed between Ramses II of Egypt and the king of the Hittites establishing "eternal peace and brotherhood" between their two nations: dealing with respect for each other’s territory and establishing a form of defensive alliance. The ancient Greeks before Alexander the Great formed many small states that constantly interacted. In peace and in war, an inter-state culture evolved that prescribed certain rules for how these states would interact. These rules did not apply to interactions with non-Greek states, but among themselves the Greek inter-state community resembled in some respects the modern international community.

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