The UN Charter law governing self-defense is inadequate to address emerging modalities of armed violence caused by non-State actors located in the territory of non-consenting third States. This paper offers an alternative grounded in the state of necessity as a circumstance excluding wrongfulness as per the law of State responsibility. The contention is that in integrating the rationale behind necessity as an excuse for non-performance of obligations and the conditions and processes under article 51 of the UN Charter, the law allows for an exercise of extraterritorial self-defense against non-State actors which safeguards the territorial State’s sovereignty and the need for a legal alternative of defense for the defending State without toeing the line of aggression.