Related Rule
Netherlands
Practice Relating to Rule 73. Biological Weapons
The Military Manual (1993) of the Netherlands states that the 1972 Biological Weapons Convention “prohibits the development, production and stockpiling of bacteriological (biological) and toxin weapons (means of warfare). Logically this implies that the use of these weapons is also prohibited.” 
Netherlands, Toepassing Humanitair Oorlogsrecht, Voorschift No. 27-412/1, Koninklijke Landmacht, Ministerie van Defensie, 1993, pp. IV-7/IV-8, § 13.
The Military Handbook (1995) of the Netherlands states: “A general prohibition applies to the use of biological (bacteriological) means of warfare. The Netherlands shall in all circumstances respect this prohibition.” 
Netherlands, Handboek Militair, Ministerie van Defensie, 1995, p. 7-39.
The Military Manual (2005) of the Netherlands states:
Section 12 - Biological (bacteriological) and toxic weapons
0459. Under the 1925 Gas Protocol it is also prohibited to use bacteriological means of warfare.
0460. Concerning such means, the Biological Weapons Convention of 1972 is now of primary importance. This Convention prohibits the development, production and storage of biological agents and toxins. The development, production and stockpiling of weapons, equipment or means of delivery to use (micro-)biological agents or toxins for hostile purposes or in an armed conflict is forbidden. Prohibition of the use of these biological weapons follows logically from this. Moreover; the use of bacteriological weapons in war was already explicitly prohibited in the 1925 Gas Protocol.
0461. Biological agents
Biological agents involve the use of living organisms (bacteria and micro-organisms such as viruses, Rickettsiae, fungi etc.) or infectious ingredients obtained from such organisms which, regardless of the type of infected material, are designed to cause sickness or death in humans, animals or plants and depend for their effect on their capacity to multiply in the person, animal or plant attacked. Substances produced by living organisms, including substances of identical or similar structure and effect, which are produced chemically and can cause sickness or death in humans, animals or plants also fall under the definition of biological agents. Examples of bacterial diseases are: anthrax, plague, tularaemia, brucellosis and Q-fever. Examples of viral illnesses are smallpox and encephalitis.
0462. Toxins
Toxins are poisonous substances produced by living organisms (bacteria, moulds, but also plants and snakes). They do not multiply in the attacked organism. One example is the Botulin toxin, which causes the disease botulism.
0463. Because modern biological weapons are not without importance from the military viewpoint, many States still prepare for the possible use of such weapons. 
Netherlands, Humanitair Oorlogsrecht: Handleiding, Voorschift No. 27-412, Koninklijke Landmacht, Militair Juridische Dienst, 2005, §§ 0459–0463.
In its chapter on non-international armed conflict, the manual states:
It is prohibited to use weapons causing unnecessary suffering or excessive injury, or that are indiscriminate. This means that biological, chemical, toxic or intoxicating weapons … are forbidden. 
Netherlands, Humanitair Oorlogsrecht: Handleiding, Voorschift No. 27-412, Koninklijke Landmacht, Militair Juridische Dienst, 2005, § 1038.
In its chapter on peace operations, the manual states: “As for the use of resources, the rules of the humanitarian law of war also apply. Thus the use of chemical or biological weapons is prohibited”. 
Netherlands, Humanitair Oorlogsrecht: Handleiding, Voorschift No. 27-412, Koninklijke Landmacht, Militair Juridische Dienst, 2005, § 1217.