This paper looks at how Hezbollah has legitimised its use of violence against Israel, distinguishing between distinct phases in its resistance. The paper compares Hezbollah’s discourse and behaviour with the ethical principles underpinning the Just War tradition (JWT) and the Islamic rulings on war. The paper contends that despite its terrorist label and the criticism surrounding its weapons, the group satisfied several conditions specified by the JWT and Islam. A big exception is the last resort criterion because, in Hezbollah’s view, armed resistance against Israel is the one and only option. Moreover, despite its intention to destroy Israel and its readiness to sacrifice fighters for this purpose, Hezbollah has shown restraint in its violence in line with the Islamic proportionality principle. Finally, the study points to the need for further research on the Islamic just war principles and on their role in judging the morality of Islamic non-state armed groups.