When the modern system of (public) international law developed from the ius gentium tradition of the late Middle Ages, it was called international law, a direct translation of the term ius gentium and rights of nations used by Hugo Grotius by Emer de Vattel. The modern concept of international law was invented by Jeremy Bentham in 1789 and was established in the 19th century.  One of the greatest achievements of the United Nations is the development of international law, which is essential to the promotion of economic and social development and the promotion of international peace and security. International law is enshrined in conventions, treaties and norms. Many of the treaties concluded by the United Nations form the basis of the law governing relations between nations. Although the work of the United Nations in this area does not always receive attention, it has a daily impact on the lives of people everywhere. Nevertheless, the idea of natural law remained influential as the basis of international law in the 17th and 18th centuries and was expressed in the works of Samuel von Pufendorf and Christian Wolff. But in the second half of the 18th century, there was a shift towards positivism in international law. Moreover, the idea of international law as a means of maintaining international peace is challenged by the growing tensions between the major European powers (France, Prussia, Great Britain, Russia and Austria).
This tension between legal norms and political imperatives is well reflected in the most important treatise of the century on international law, Du Droit des Gens (1758) by Emer de Vattel. At the end of the century, Immanuel Kant believed that international law, as a law that could justify war, no longer served the purpose of peace, and therefore argued in On Eternal Peace (1795) and The Metaphysics of Morality (1797) for the creation of a new type of international law. A historically informed suggestive departure from traditional approaches that shifts the emergence of international law to the 18th century. A modern examination of what the author presents as the dual liberal-welfare-oriented structural normative framework that underpins international law and continues to the present day. Until the middle of the 19th century, relations between states were mainly dictated by treaties, agreements between states to behave in a certain way, unenforceable except by force, and non-binding, except as matters of honor and loyalty. One of the earliest instruments of modern international law was the Lieber Code of 1863, which regulated the conduct of the United States. Armed Forces during the American Civil War and is considered the first written recitation of the rules and articles of war observed by all civilized nations. This led to the first war crimes indictment, in which a Confederate commander was tried and hanged for holding prisoners of war in cruel and depraved conditions in Andersonville, Georgia.
In the following years, other states pledged to restrict their conduct, and many other treaties and bodies were created to regulate the conduct of states among themselves, including the Permanent Court of Arbitration in 1899 and the Hague and Geneva Conventions, the first of which was adopted in 1864. This system developed under the aegis of the United Nations Economic and Social Council, which established the Commission on Human Rights under Article 68 of the Charter of the United Nations. The Commission was not composed of independent experts, but of 54 governmental representatives elected by the Council, regardless of the human rights record of the States concerned. Accordingly, States identified as some of the worst perpetrators of human rights violations were members of the Commission. The Commission`s main achievement has been the elaboration and near-universal acceptance of the three main international human rights instruments: the Universal Declaration of Human Rights adopted in 1948, the International Covenant on Civil and Political Rights (ICCPR) and the International Covenant on Economic, Social and Cultural Rights (ICESCR), the latter two adopted in 1966. As the adoption of these two separate documents shows, the original idea of transforming the Universal Declaration of Human Rights into a single binding instrument was not realized, mainly because there was no agreement on the applicability of socio-economic rights. As a result, individual complaints of violations of the International Covenant on Civil and Political Rights could be filed by some States, but not by the ICESCR. The Peace Palace Library has an impressive collection of old and rare books of 10,000 titles printed before 1850.
Since 1913, the library has had a historical legal collection representing the different periods of reflection on international law, dominated by Spanish, French or English schools. Writers of the 16th century: Jean Bodin, Ayala, Vitoria, of the 17th century: Hugo Grotius, Gentili, Pufendorf, Zouche and of the 18th century. Bynkershoek, Wolff, Martens, Vattel and Bluntschli from the 19th century, to name but a few. In total, about 2400 authors represent the origins of international law. Modern authors on international history refer to these sources for their research. After the First World War, attempts were made to establish a human rights system under the aegis of the League of Nations. For example, a minority committee had been established to hear minority complaints, and a mandate commission had been established to consider individual petitions from persons living in mandated territories. However, these attempts were not very successful and ended abruptly with the outbreak of World War II.
It took the trauma of that war, and in particular Hitler`s racially motivated gross atrocities in the name of Nazism, to cement international consensus in the form of the United Nations as a bulwark against war and for the preservation of peace. “If legislation is the enactment of laws by a person or assembly that binds the whole community, there is no international law. Because contracts only bind those who sign them. The principles of early Islamic law on military conduct and the treatment of prisoners of war under the early caliphate are considered precursors of international humanitarian law. Among the many requirements for the treatment of prisoners of war are, for example, the provision of shelter, food and clothing, respect for their culture and the prevention of execution, rape or acts of revenge.