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 Sovereign, that is the emperor of China.

The Peace Palace Library has an impressive old and rare books collection of 10.000 titles printed before 1850. Since 1913 the Library has acquired a historical legal collection representing the various periods of thinking about international law, dominated by the Spanish, French or English schools. Writers from the 16th century: Jean Bodin, Ayala, Vitoria, the 17th century: Hugo Grotius, Gentili, Pufendorf, Zouche, and 18th century: Bynkershoek, Wolff, Martens, Vattel, and 19th century Bluntschli, to name only a few. In total about 2400 authors represent the origins of international law. Modern authors on the history of international law refer to these sources for their research.

This Research Guide is intended as a starting point for research in the field of the History of International Law. It provides the basic materials available in the Peace Palace Library, both in print and electronic format. Handbooks, leading articles, bibliographies, periodicals, serial publications and documents of interest are presented in the Selective Bibliography section. Links to the PPL Catalogue are inserted. The Library's subject heading (keyword) History of International Law is instrumental for searching through the Catalogue. Special attention is given to our subscriptions on databases, e-journals, e-books and other electronic resources. Finally, this Research Guide features links to relevant websites and other online resources of particular interest.