The term ius gentium or law of nations, was used in ancient Roman law to describe the laws that governed the interactions between Romans and non-Romans, based on the principles of natural justice that did not depend on the state of both parties but on that of a Roman citizen. This was significant in ancient Roman law, where law and state were intertwined, to suggest that there was a universal standard of justice. This term was first modulated in Institutes of Gaius, the standard text and commentary of the Twelve Tables of Roman law, which was completed around 160 AD.
In a general sense, the ius gentium or of the peoples, can be observed among all peoples without distinction of nationalities. Since they were that group of habitual rules that governed all Roman citizens and foreigners. It should be noted that the law of nations is close to natural law, but these should not be confused since, for example, slavery that was accepted by all ancient peoples as a law of nations, but by classical jurists was recognized as contrary to law. natural.
In legal theory, the law that natural reason establishes for all men, unlike jus civile, or the civil law proper to a state or people. Roman lawyers and magistrates originally devised jus gentium as a system of fairness of application to cases between foreigners and Roman citizens. The concept originated from the Roman assumption that any rule of law common to all nations must be fundamentally valid and just. They expanded the concept to refer to any standard that instinctively praised their own sense of justice. In time the term became synonymous with equity, or the law of the praetorium. In modern law, there is a distinction between privatum jus gentium, which denotes private international law, also known as conflict of laws, and publicum jus gentium, which denotes the system of rules governing relations between nations.
