International humanitarian law, or jus in bello, has its foundations in the thoughts of thinkers such as Thomas Aquinas, Aristotle, Plato, as well as many more. It is the law that governs the way in which states conduct warfare in an attempt to make it less violent and as morally acceptable as possible. These ideas became the foundations of international law, as their philosophy is present in various famous international treaties such as the Treaty of Versailles, the 1856 Paris Declaration on Maritime Warfare, and the Geneva Convention.
Jus in bello, when combined with jus ad bellum (the conditions under which waging war is acceptable), attempts to limit the violence and number of wars and has many significant demands in order to ensure that a war between states is just.
The first is that states must identify who and what are legitimate targets during war. The second is that actions in war must be proportional to the actions of opponents, that military action should be proportional to the desired goal, and that weapons capable of damaging both legitimate and illegitimate targets simultaneously are forbidden. The final rule jus in bello advocates is that prisoners of war must be humanely treated and are entitled to basic human rights and respect (Maiese, 2003).
Despite the principles of jus in bello forming many modern understandings of the guidelines of war, there is a doctrine known as the Supreme Emergency (SE) Doctrine that challenges its principles. This is because the SE Doctrine, created by realist thinkers such as John Mearsheimer and advocated for by thinkers such as Winston Churchill and Michael Walzer, argues that constraints on warfare are illegitimate, as there are circumstances in which states are entitled to do whatever it takes to achieve victory. As a result, this doctrine challenges jus in bello in several ways (Walzer, 2015).
The first is that the SE Doctrine argues that if a country’s freedom or existence is under threat, then jus in bello can be ignored. The second is that if a state is not fighting another state, jus in bello does not apply. The final contradiction is that a leader has a greater obligation to the safety of their own people than to prisoners of war or the people of an opponent nation.
As mentioned, the first main principle of jus in bello is that states at war should make a clear distinction between legitimate and illegitimate targets. This is because killing is morally wrong; therefore only targets such as military bases, soldiers, railways, and infrastructure used for the war effort are legitimate.
Soldiers and other war actors have sacrificed some of their basic human rights and safety by inflicting violence on behalf of their state, with many joining voluntarily. Their deaths and the destruction of their equipment can therefore be justified due to their willingness to be put in danger (Maiese, 2003).
Civilians, schools, hospitals, places of worship, and other non-military targets have not surrendered such rights and do not contribute to the war effort, making attacks on them morally indefensible. The doctrine of double effect acknowledges that civilian casualties may occur accidentally during attacks on legitimate targets.