International law prohibits the States to use force or extends any threat to use force in any manner against the territorial integrity and sovereignty of any other State. This prohibition is confirmed by the Charter of UN and it is part of international customary law as well. There is an exception to this prohibition provided by Article 51. This Article recognizes the right to self-defense of a State when it is assaulted by another State. The question is whether this right to self - defense be used against non -State actors as well and what should be done if these non- state actors are operating from the locality of another State. This study analyzes the scope of right to self- defense. It further discusses the legality of State practice to use extra territorial force against non-state actors. The doctrinal research methodology is opted for this research paper. This research provides an analysis of legal provisions, customary law and State practices related to the extraterritorial force against non- State actors. It suggests that the existing legal framework (UN charter and treaties) doesn’t address the subject of exercising self defense against non- state actors and the state practices has not yet acquired the status of customary law as it misses the necessary element of opinio juris. Therefore, uniform legal rules should be adopted by States to avail the benefit of self- defense provisions against non- state actors.