Killing in war as a matter of course may be inferred from the fact that, as stated by Thomas Hobbes, “all laws are silent in the time of war”. Although this traditional law-suspending power of war has been restricted to a certain degree by modern humanitarian international law, it is still commonly assumed that killing in war, unless and as long as not explicitly forbidden, is per se permitted and thus does not require any further legitimisation. This is in fundamental (...) contrast to a “normal” homicide, which requires special justification to be considered lawful. This commonly unquestioned license to kill, by the mere reason of being at war, is all the more astonishing given that no legal norm can be found that positively and explicitly declares killing in war to be lawful. However, on what ground can such an unwritten privilege be based? How can it be morally justified and sufficiently legitimised? This question shall be pursued in four steps: by, first, asking whether and why killing in war, as long as it does not cross the threshold of a war crime, shall stay outside the rubric of criminal law. After not having found a satisfactory answer, it must, second, be asked whether and to what degree constitutional law could provide empowerments and restrictions of killing in war. As neither will give full answers, third, final refuge may be taken in international law, with particular attention to state sovereignty. Since even on this level, however, killing in war has not yet found convincing legitimisation, fourth, further challenges are to be met. (shrink)