Page "Public international law" Paragraph 39

In 1625 Hugo Grotius argued that nations as well as persons ought to be governed by universal principle based on morality and divine justice while the relations among polities ought to be governed by the law of peoples, the jus gentium, established by the consent of the community of nations on the basis of the principle of pacta sunt servanda, that is, on the basis of the observance of commitments.

On his part, Emmerich de Vattel argued instead for the equality of states as articulated by 18th century natural law and suggested that the law of nations was composed of custom and law on the one hand, and natural law on the other.

During the 17th century, the basic tenets of the Grotian or eclectic school, especially the doctrines of legal equality, territorial sovereignty, and independence of states, became the fundamental principles of the European political and legal system and were enshrined in the 1648 Peace of Westphalia.