Related Rule
Practice Relating to Rule 70. Weapons of a Nature to Cause Superfluous Injury or Unnecessary Suffering
Ecuador’s Naval Manual (1989) provides:
It is a fundamental tenet of the law of armed conflict that the right of nations engaged in armed conflict to choose methods or means of warfare is not unlimited. This rule of law is expressed in the prohibition of the employment of weapons, material, and methods of warfare that are designed to cause superfluous injury or unnecessary suffering.
Antipersonnel weapons are designed to kill or disable enemy combatants and are lawful notwithstanding the death, pain, and suffering they inflict. Weapons which cause superfluous injury or unnecessary suffering are, however, prohibited because the degree of pain, the severity of the injuries and the certainty of death they entail are clearly out of all proportion to the military advantage sought. Poisoned projectiles and dum-dum bullets belong in this category since the small military advantage that may be derived from their use guarantees death due to poisoning or to the expanding effect of soft-nosed or unjacketed lead bullets.
Similarly, using materials that are difficult to detect or undetectable by field X-ray equipment, such as glass or clear plastic, as the injuring mechanism in military ammunition is prohibited, since they unnecessarily inhibit the treatment of wounds. 
Ecuador, Aspectos Importantes del Derecho Internacional Marítimo que Deben Tener Presente los Comandantes de los Buques, Academia de Guerra Naval, 1989, §§ 9.1 and 9.1.1.
In its written statement submitted to the ICJ in the Nuclear Weapons case in 1995, Ecuador stated: “The use of nuclear weapons contradicts the humanitarian dispositions against the use of warlike artifacts that provoke cruel and unnecessary sufferings to its victims.” 
Ecuador, Written statement submitted to the ICJ, Nuclear Weapons case, 20 June 1995, p. 2, § D.