Legitimate –Defense or Violation of International Rules in the Assassination of Sardar Soleimani

Until the early twentieth century, war and coercion were the most important  governing  principle on relations between countries, but occurrence two world wars with short interval led the charter setters of the United Nations to use force as a destructive factor in international relations, and make the prohibition on use of force  as one of the fundamental principles of international law for the postwar period. Of course, the Charter, in some  cases  allows  to  exert  the inherent right to a Self-defense and collective security system as an exception. Research method is Descriptive-analytical and for collecting information, fishing  tool with library study have been used. We seek to answer these questions: First, where is the position of the use of force and legitimate defense in international law? Second: The US action, in the assassination of Sardar Soleimani, was legitimate or a behavior to justify the use of force in international relations? The findings show that the use of force is prohibited under international law, and the right of legitimate defense of states is recognized only when subjected to armed attacks. Therefore, the US action is clearly contrary to Article 51 of the Charter and has no congruence  to other  international  principles.