 Much interaction at the system level is governed by them, and they outlaw some traditional institutions and practices of international relations, such as the use of war (except in self-defence).The United Nations (UN) is an international organization that describes itself as a "global association of governments facilitating co-operation in international law, international security, economic development, and social equity"; It is the most prominent international institution.Many of the legal institutions follow the same organizational structure as the UN.