Related Rule
South Africa
Practice Relating to Rule 73. Biological Weapons
South Africa’s LOAC Manual (1996) states: “The use of certain weapons is expressly prohibited by international agreement, treaty or custom (e.g. biological and toxic weapons).” 
South Africa, Presentation on the South African Approach to International Humanitarian Law, Appendix A, Chapter 4: International Humanitarian Law (The Law of Armed Conflict), National Defence Force, 1996, p. 12, § 34.f.(iii).
South Africa’s Revised Civic Education Manual (2004) states:
i. Prohibited Weapons. The following weapons have been prohibited:
(3) … Bacteriological Weapons. Geneva Protocol outlawing their use in 1925. This ban was later strengthened by the adoption of the Biological Weapons Convention (1972) … which prohibits the development, production, stockpiling and transfer of such weapons. 
South Africa, Revised Civic Education Manual, South African National Defence Force, 2004, Chapter 4, § 56(f)(i).
South Africa’s Non-Proliferation of Weapons of Mass Destruction Act (1993) provides:
The Minister may, by notice in the Gazette, determine the general policy to be followed with a view to:
(d) the imposition of a prohibition, whether for offensive or defensive purposes, on the development, production, acquisition, stockpiling, maintenance or transit of any weapons of mass destruction. 
South Africa, Non-Proliferation of Weapons of Mass Destruction Act, 1993, Section 2(1)(d).
In its judgment in the Basson II case in 2005, the Constitutional Court of South Africa stated:
[179] … There can be no doubt that the use of instruments of state to murder captives long after resistance had ceased would in the 1980s, as before and after, have grossly transgressed even the most minimal standards of international humanitarian law.
[180] The same has to be said of … the provision of cholera bacteria for placement in water supplies. Such means of warfare are abhorrent to humanity and forbidden by international law. … In 1925 the Geneva Protocol prohibited the use of chemical and bacteriological weapons. In 1972 the ban on bacteriological means of warfare was restated and strengthened by a specific convention designed to prohibit the manufacture and stockpiling of these agents of destruction. 
South Africa, Constitutional Court, Basson II case¸ Judgment, 9 September 2005, §§ 179–180.
At the Fourth Review Conference of States Parties to the Biological Weapons Convention in 1996, South Africa declared that it remained “committed to achieving a world free of all weapons of mass destruction and to addressing the proliferation of conventional weapons”. It also reaffirmed its “commitment to strengthening the [Biological Weapons Convention] by establishing a verifiable compliance protocol for the Convention”. 
South Africa, Statement of 26 November 1996 at the Fourth Review Conference of States Parties to the Biological Weapons Convention, Geneva, 25 November–6 December 1996.
At the Fifth Review Conference of States Parties to the Biological Weapons Convention in 2001, South Africa stated: “The use of disease – in this case anthrax – as a weapon of terror should … be condemned in the strongest possible terms.” It further emphasized
the importance of the work that had been undertaken to negotiate a legally binding Protocol to strengthen the implementation of the Convention … South Africa continues to see the strengthening of the implementation of the [Biological Weapons Convention] as a core element of the international security architecture. 
South Africa, Statement of 19 November 2001 at the Fifth Review Conference of States Parties to the Biological Weapons Convention, Geneva, 19 November–7 December 2001.