The Westphalian system is the political order in international law that each state has exclusive sovereignty over its territory and are the monopolists of the ability to conduct warfare.STRANGE, S. (1999). The Westfailure system. Review of International Studies, 25(3), 345-354. doi:10.1017/S0260210599003459 The principle developed in Europe after the Peace of Westphalia in 1648, based on the state theory of Jean Bodin and the natural law teachings of Hugo Grotius. It underlies the modern international system of sovereign states and is enshrined in the United Nations Charter, which states that "nothing ... shall authorize the United Nations to intervene in matters which are essentially within the domestic jurisdiction of any state."
