Practice Relating to Rule 53. Starvation as a Method of Warfare
Section B. Sieges that cause starvation
Israel’s Manual on the Laws of War (1998) states:
Siege as a method of warfare vis-a-vis a military objective is an absolutely legal method even if it involves the starvation of the besieged or preventing the transfer of medications in order to achieve surrender.
A question arises in the case of a military siege of an inhabited city. Until recently there were no rules relating to this method of warfare, and it was allowed to exploit the suffering of the local population in order to subdue the enemy. Following the Second World War, a provision was set in the Additional Protocols of 1977, forbidding the starvation of a civilian population in war. This provision clearly implies that the city’s inhabitants must be allowed to leave the city during a siege.
Israel’s Manual on the Rules of Warfare (2006) states:
A siege of a military target is a completely legitimate means of warfare, even if it involves the starvation of the besieged soldiers. A question arises in the case of a military siege of a populated town. Until recently, there were no rules attached to this method of warfare, and it was permitted to exploit the suffering of the local population in order to overcome the enemy. The  Additional Protocols to the Geneva Convention contain a provision banning starvation of the civilian population in battle. The meaning to be extracted from this provision is that the residents of a city need to be allowed to leave it if it is besieged. In cases where civilians do not have the opportunity to leave the besieged city, a duty arises to supply them with food, water and humanitarian aid.
The Manual on the Rules of Warfare (2006) is a second edition of the Manual on the Laws of War (1998).