On January 1, an explosion occurred in the capital Volvor by the non-state organization “The Assassin” based in the territory of Polor. In which state property was damaged and numerous civilians were killed. No involvement was demonstrated on the part of the State of Polor which also declared itself powerless to prevent the organisation's activities. Exercising the right of self-defense under Article 51 of the UN Charter, the state of Volvor attacked in the territory of Polar, considering it the headquarters of the “Assassin”, with the aim of bringing the main leader to justice of the organization. As a result, not only was the goal of targeting the leaders achieved, but numerous innocent civilian casualties occurred during the retaliation. The issue requires a discussion of law regarding the legality of the use of force in self-defense against armed attacks by non-state actors as entities within the territory of a foreign state, along with the principle of necessity and proportionality. The rule of Article 51 is that the attack must be attributed to the foreign state. In this case, evidence is needed that Polor has complete control over “The Assassin” as a de facto state organ or has effective control over the act in question of “The Assassin”. Since there is no evidence of either against the State of Polor, the armed attack cannot be attributed to Polor. The September 11 attacks are the emblematic example of non-state actors where attacks on the United States (US) were carried out while organizing from the territory of another state. On October 7, 2001, the United States responded to attacks by targeting Taliban and Al-Qaeda camps in Afghanistan. The international community also recognized the US invasion of Afghanistan… halfway through the document… fully exercised its inherent right to self-defense using force under Article 51 of the United Nations Charter, despite the proportionality of casualties caused by the The deed of Volvor are different from the calamities of Polor. Seeing the case of Polor and Volvor, it can be said that it is the duty of the state itself to protect its citizens and residents from any domestic or foreign attack, when the perpetrators plan and execute the attacks while conspiring outside the state's borders and when the host state fails to take necessary measures against such acts of non-state groups. Furthermore, Volvor's use of force is justified and does not constitute a violation of Polor's sovereignty because Article 51 authorizes the victim state to use force in self-defense to mitigate anticipated threats, in response to such armed attack by non-state actors..