This paper aims at assessing the pacifist claim that the military licence to kill cannot be derived from the right to self-defense. Two clear-cut theories of self-defense, the causal theory and the strong moral theory, fuel two radically opposed conclusions. Indeed, the causal theory supports the classical Just War Doctrine (Walzer),while the strong moral theory supports pacifism. They are two extreme options among a complex set of possible theories of self-defense. I, nonetheless, defend the view that the strong moral theory does remain the most promising one. Whence it follows that, from the point of view of self-defense, pacifism is better established than the classical Just War Doctrine. This Doctrine may only be saved by endorsing rather some form of moral collectivism.