Events such as the armed conflicts in the former Yugoslavia; between Iraq and Iran or Ethiopia and Eritrea; in Afghanistan, Iraq, Sudan, Rwanda, the Congo, Somalia, Sri Lanka and Colombia, remind us day after day of the cruelty of war and the suffering, death and destruction it entails. They also raise an obvious question: is the behaviour of the parties to such armed conflicts subject to any restrictions? The answer is that such restrictions do exist, even though they may not always be crystal clear or completely unequivocal. Confining ourselves to the realm of law (rather than that of morality alone) they are found in such diverse branches as the law of the United Nations Charter, human rights law, environmental law, the law of neutrality and, last but not least, the ‘law of war’ or jus in bello: a body of law specifically designed to ‘constrain the waging of war’.