The UN Security Council is the only authority to prescribe the right to legal use of force on the basis of legal principles and rules.  The 1937 Convention on the Suppression and Punishment of Terrorism (Geneva Convention) is the first international convention on terrorism. The process and mechanisms needed to define and delineate counterterrorism in international law are very slow. The US government has often used the Security Council mechanism, and otherwise, by force or concluding incomplete treaties with some countries, to justify its illegal actions internationally. The assassination is considered to be the most effective senior military official in command of the Takfiri Counter-Terrorism Front in the US-led region, under the direct command of the US President. The following article examines the assassination of General Suleimani for violating the principles of international and domestic law. This article states that citing a defense by the United States lacks the necessary elements to assign action to Iran. The claim of preventive defense is also not approved by international judicial custom. The perspective of international lawyers not only confirms the matter, but also denies it and opposes it. The US military attack on January 3, was contrary to the Iraqi -US security agreement and the Roman statute, and is a case of violations and violations.