Some of the confusion might be from the regulation that governs the Law of Land Warfare; it seems to me to be somewhat ambiguous. (see excerpt below)
Section III. FORBIDDEN MEANS OF WAGING WARFARE
33. Means of Injuring the Enemy Limited
a. Treaty Provision.
The right of belligerents to adopt means of injuring the enemy is not unlimited. (HR, art. 22.)
b. The means employed are definitely restricted by international declarations and conventions and by the laws and usages of war.
34. Employment of Arms Causing Unnecessary Injury
a. Treaty Provision.
It is especially forbidden * * * to employ arms, projectiles, or material calculated to cause unnecessary suffering. (HR, art. 23, par. (e).)
b. Interpretation. What weapons cause "unnecessary injury" can only be determined in light of the practice of States in refraining from the use of a given weapon because it is believed to have that effect. The prohibition certainly does not extend to the use of explosives contained in artillery projectiles, mines, rockets, or hand grenades. Usage has, however, established the illegality of the use of lances with barbed heads, irregular-shaped bullets, and projectiles filled with glass, the use of any substance on bullets that would tend unnecessarily to inflame a wound inflicted by them, and the scoring of the surface or the filing off of the ends of the hard cases of bullets.
