This fundamental principle is supplemented by another part of the 1977 protocol, which further defines that attacks should be limited to military objectives. This also prohibits indiscriminate attacks. Meanwhile the protocol also establishes the principle of proportionality, which bans attacks where civilian losses would be excessive in terms of the military objective, and the principle of precaution, which governs precautions that must be taken before an attack on a military objective.
The principle of humanity, which “forbids the infliction of all suffering, injury or destruction not necessary for achieving the legitimate purpose of a conflict”, permeates the whole body of contemporary international humanitarian law and responds to the 19th century and discredited German doctrine of Kriegraison.
That doctrine says that in times of war, military necessity negates all other considerations. Modern international humanitarian law utterly rejects this idea and sets limits on the conduct of hostilities and the means and methods of warfare.
So, based on these provisions of international humanitarian law, targeting civilians and civilian objects in the way we have seen during Russia’s invasion of Ukraine is a flagrant violation of the laws of armed conflict. In simple terms, it is a war crime.
The 1977 additional protocol also prohibits the starvation of civilians. It forbids attacks on objects indispensable to the survival of the civilian population, such as food supplies and drinking water installations, among others. This is also recognised as a war crime under the Rome Statute, which is the founding instrument of the International Criminal Court in 1998 and also under “customary” international law, which exists parallel to treaty law.
So, while international law doesn’t actually prohibit siege warfare, it puts firm limits when civilians are affected. It prescribes that: