This thesis aims to study how Hezbollah acted just or unjustly in the 2006 Lebanon War to conclude if their warfare was just or unjust. That leads to a better understanding of Hezbollah's warfare in the 2006 Lebanon War and if they thereby have culpability in the war. If Hezbollah want to be taken as a serious and legitimate force in war, they should be held accountable to the same standards of warfare as states and be shown that there are consequences for their actions. The theory that will be used in order to do so, is the Just War theory. It is divided into two categories: Jus ad Bellum, the right to go to war, and Jus in Bello, the right conduct in war. Hezbollah seemed to have failed to meet the criteria of Jus ad Bellum, by failing to fulfill the criteria just cause, right intention, the proportionality of ends, and a reasonable prospect of success. They only managed to fulfill the criterion of right authority and mostly the last resort criterion, due to their constitutional right to wage war and their prior intents of a prisoner exchange. The organization also failed to meet the criteria of Jus in Bello: proportionality of means and discrimination. They had no proportionality regarding the goal, nor did they differentiate between military goals and civilians. It was therefore concluded that Hezbollah acted unjustly in the 2006 Lebanon War, by not having the right to go to war, but also because the conduct in the war was unjust as well. That contributed to the more significant understanding of Hezbollah's warfare in the 2006 Lebanon War including its culpability, and the importance of holding them accountable for their actions in war. / Krishantering och säkerhet