Questions regarding responsibilities in war are deeply related to moral discussions. Just war theory is a theory developed in order to categorize in which ways a war can be performed to be as just as possible. The theory was primarily divided into two dimensions: jus ad bellum and jus in bello which focuses on the reasons for going to war and the execution of the war. In recent years a third component to the theory has been discussed which incorporates the responsibilities after a war has been terminated, also known as jus post bellum. In this essay, just war theory is applicable to NATO:s invasion, Operation Unified Protector (OUP), of Libya during the civil war in 2011. In order to do so, a qualitative study has been chosen as methodology based on primary and secondary sources. By analyzing NATO:s actions from a just war perspective, the results present that the invasion was just based on jus ad bellum and jus in bello. The jus post bellum dimension did, in this case study, weaken OUP from a just war perspective as very few post war measures were implemented and sustainable peace did not arise after the operation ended.