Related Rule
Sri Lanka
Practice Relating to Rule 70. Weapons of a Nature to Cause Superfluous Injury or Unnecessary Suffering
In its written statement submitted to the ICJ in the Nuclear Weapons (WHO) case, Sri Lanka stated:
Customary law principles which have evolved in the field of armed conflict prohibit the use of weapons and the methods of warfare of a nature to cause superfluous injury or unnecessary suffering. 
Sri Lanka, Written statement submitted to the ICJ, Nuclear Weapons (WHO) case, undated, p. 2.