International law works with no police force and no final judge
Treaties between states stretch back to about 3100 BCE, when the Mesopotamian cities of Lagash and Umma made peace. Yet international law still has no universal authority to enforce it. It runs mostly on consent, and states that break it risk disapproval, sanctions or, at worst, war.
International law is the body of rules, customs and norms that states and other actors feel bound by, and usually follow, in dealing with one another. Its sources are treaties, custom accepted as law, and general legal principles shared by most national systems. Polite practices known as comity, like reciprocal courtesies, carry no legal force. Without a final arbiter, each state interprets the rules for itself, and powerful countries can push harder on what counts as lawful because they can impose heavier costs.
Jeremy Bentham coined the term in 1789 to replace the old law of nations, drawn from the Roman ius gentium. One of the most famous early agreements was struck between Ramesses II of Egypt and the Hittite king Hattusili III in 1279 BCE. In China's Spring and Autumn period, rival states worked out rules on just causes for war, neutral parties and treaty-making, and Indian states developed their own codes of neutrality and conduct.
Medieval Europe, split among church, kingdoms and trading cities, relied on canon law, merchant law and maritime codes such as the Rolls of Oléron and the Hanseatic Laws of Wisby. In the eighth century the Islamic jurist al-Shaybani wrote a foundational work on foreign relations whose rules on distinguishing civilians from fighters and caring for the wounded foreshadowed humanitarian law. Maimonides and Thomas Aquinas blended natural law with religious principle to judge when a war was just. Francisco de Vitoria, troubled by Spain's treatment of indigenous peoples, argued for their innate dignity and an early idea of equality between peoples.
Scholars distinguish public international law, which governs states and international bodies, from private international law, which asks which country's courts and rules apply to cross-border cases. The European Union goes further still, a supranational system whose members hand some lawmaking to shared institutions.
Source: International law
