Related Rule
Russian Federation
Practice Relating to Rule 70. Weapons of a Nature to Cause Superfluous Injury or Unnecessary Suffering
The Russian Federation’s Military Manual (1990) provides:
Prohibited means of warfare are the various weapons of an indiscriminate character and/or those that cause unnecessary suffering:
a) bullets that expand or flatten easily in the human body;
b) projectiles used with the only purpose to spread asphyxiating or poisonous gases;
c) projectiles weighing less than 400 grammes, which are either explosive or charged with fulminating or inflammable substances;
d) poisons or poisoned weapons;
e) asphyxiating, poisonous or other similar gases and bacteriological means;
f) bacteriological (biological) and toxin weapons;
g) environmental modification techniques having widespread, long-term or serious effects as means of destruction, damage or injury;
h) all types of weapons of an indiscriminate character or that cause excessive injury or suffering. 
Russian Federation, Instructions on the Application of the Rules of International Humanitarian Law by the Armed Forces of the USSR, Appendix to Order of the USSR Defence Minister No. 75, 1990, § 6.
In its written statement submitted to the ICJ in the Nuclear Weapons case in 1995, the Russian Federation stated:
As to the attempts to justify the illegitimacy of the use of nuclear weapons by references that they cause “unnecessary sufferings while injuring, uselessly aggravate the sufferings of disabled men, or render their death inevitable”, they are … hardly reasonable … The reasonable comments of the ICRC confirm two considerations … The principle of not causing “unnecessary suffering” is not in itself a general ban on the use of nuclear weapons as such …
[The 1977 Additional Protocol I] reproduces, with slight changes (Art. 35), the above-mentioned provisions of the [1907 Hague Convention IV and the 1907 Hague Regulations], but they, being treaty norms, are not applied to nuclear weapons …
The view that the said blanket formulas are not considered by the international community as a whole as a general ban on the use of specific types of weapons, including nuclear weapons as such, is supported by the fact that international law did not choose the option of a special ban of particular types of weapons and their use. That is how … the 1980 Convention on the Prohibition or Restrictions on the Use of Certain Conventional Weapons, which May Be Deemed to Be Excessively Injurious or to Have Indiscriminate Effects, together with the Protocols thereto … appeared. 
Russian Federation, Written statement submitted to the ICJ, Nuclear Weapons case, 19 June 1995, pp. 12–14.
In its oral pleadings before the ICJ in the Nuclear Weapons case in 1995, the Russian Federation stated:
References to the effect that nuclear weapons cause “unnecessary sufferings while injuring, uselessly aggravate the sufferings of disabled men, or render their death inevitable”, and, thus, to Article 23 (a) of the Regulation on the Laws and Customs of War on Land annexed to the 1907 Hague Convention with the aim to justify the illegality of their use can hardly be considered as appropriate … These reasonable comments of the ICRC experts [contained in the report entitled “Weapons that May Cause Unnecessary Suffering or Have Indiscriminate Effects”] confirm that the principle of not causing “unnecessary suffering” is not in itself a general ban on the use of nuclear weapons per se. This is also confirmed by the fact that international law did embark on the road of a special ban of particular types of weapons and their use. That is how appeared the … 1980 Convention on Prohibitions or Restrictions on the Use of Certain Conventional Weapons which May Be Deemed to Be Excessively Injurious or to Have Indiscriminate Effects, together with the Protocols thereto. 
Russian Federation, Oral pleadings before the ICJ, Nuclear Weapons case, 10 November 1995, Verbatim Record CR 95/29, pp. 45-46.