International law

International law, often called public international law or the law of nations, is a framework of rules and standards. These rules govern the mutual relations between states and other international actors. Actors include individuals, states, international organizations, and non-state groups. These entities make behavioral choices that can be lawful or unlawful. The system establishes norms across many domains, such as diplomacy, war, economic relations, and human rights.

To understand this system, one must distinguish between rules and norms. Rules are formal, written expectations that outline required behavior. Norms are informal, unwritten guidelines shaped by custom and social practice. International law operates differently than domestic legal systems because it relies largely on consent. There is no universally accepted global authority to enforce laws upon sovereign states. Because of this, states may choose to breach a treaty or ignore a norm. Such violations can result in disapproval, economic sanctions, diplomacy, or even war.

There are several distinct types of international legal frameworks. Public international law covers rules with an international origin. In contrast, private international law deals with whether national courts have jurisdiction over foreign cases. Some scholars use the term transnational law to describe rules that transcend national frontiers. Another concept is supranational law, which is a relatively new political term. In a supranational system, nations explicitly cede decision-making power to a shared judiciary and legislature. The European Union serves as the most common example of this integrated system.

History shows that states have negotiated agreements since antiquity. One of the earliest recorded examples is a peace treaty between Mesopotamian city-states around 3100 BCE. Another significant agreement occurred in 1279 BCE between Pharaoh Ramesses II and Hittite King Ḫattušili III.

The Roman Empire established the concept of *jus gentium*. This framework governed the status of foreigners living in Rome. In China, rules for diplomacy and treaty-making emerged during the eighth century BCE. During the Warring States period, Confucianism and Legalism provided different principles to guide foreign relations.

During the Middle Ages, various specialized legal systems emerged to provide stability. In Europe, *lex mercatoria*, or merchant law, regulated trade and commerce. Maritime codes like the Rolls of Oléron regulated shipping in North-western Europe. In the Islamic world, Muhammad al-Shaybani published *Al-Siyar Al-Kabīr* in the eighth century. This work governed foreign relations by dividing the world into different legal categories. These Islamic principles regarding military conduct acted as precursors to modern international humanitarian law.

The Renaissance brought the emergence of modern international law through key thinkers. Francisco de Vitoria is often called the originator of modern international law for his work on sovereign equality. In 1625, the Dutch jurist Hugo Grotius published *De Jure Belli ac Pacis*. Grotius is widely regarded as the father of international law because he envisioned a society of states governed by law rather than force.

Later, Jeremy Bentham coined the specific term "international law" in his 1789 book. Lassa Oppenheim provided a definition based on the common consent of sovereign and equal states.

International law is deeply connected to national legal systems. National law can become international law when treaties permit jurisdiction for supranational tribunals. For instance, the Geneva Conventions require national laws to conform to specific treaty provisions. This connection allows international obligations to be integrated into domestic law through national constitutions. The relationship remains complex, as states can interpret international law in ways they see fit. This can lead to significant local effects when different interpretations are applied.