Related Rule
Israel
Practice Relating to Rule 18. Assessment of the Effects of Attacks
Israel’s Manual on the Laws of War (1998) states: “The commander is required to refrain from an attack that is expected to inflict harm on the civilian population that is disproportionate to the expected military gain.” 
Israel, Laws of War in the Battlefield, Manual, Military Advocate General Headquarters, Military School, 1998, p. 40.
Israel’s Manual on the Rules of Warfare (2006) states:
The rules of war have laid down a number of rules of engagement in a theatre of war containing civilians:
- Even if it is not possible to isolate civilians from the military target and there is no choice but to attack, the commanding officer is required to refrain from conducting an attack that could be expected to cause the civilian population damage that is disproportionate to the expected military gain. 
Israel, Rules of Warfare on the Battlefield, Military Advocate-General’s Corps Command, IDF School of Military Law, Second Edition, 2006, pp. 27–28.
The Manual on the Rules of Warfare (2006) is a second edition of the Manual on the Laws of War (1998).