Related Rule
Australia
Practice Relating to Rule 71. Weapons That Are by Nature Indiscriminate
Australia’s Commanders’ Guide (1994) states:
Some weapons and weapons systems are totally prohibited. These blanket prohibitions, which may be traced to treaty or customary international law, are justified on the grounds that the subject weapons are either indiscriminate in their effect or cause unnecessary suffering. 
Australia, Law of Armed Conflict, Commanders’ Guide, Australian Defence Force Publication, Operations Series, ADFP 37 Supplement 1 – Interim Edition, 7 March 1994, § 304.
The Guide also states: “Both chemical and biological weapons are prohibited because they cause unnecessary suffering and may affect the civilian population in an indiscriminate fashion.” 
Australia, Law of Armed Conflict, Commanders’ Guide, Australian Defence Force Publication, Operations Series, ADFP 37 Supplement 1 – Interim Edition, 7 March 1994, § 306.
The Guide goes on to say that poison or poisoned weapons are prohibited “because of their potential to be indiscriminate in application”. 
Australia, Law of Armed Conflict, Commanders’ Guide, Australian Defence Force Publication, Operations Series, ADFP 37 Supplement 1 – Interim Edition, 7 March 1994, § 307.
With respect to weapons deemed to be legal, the Guide notes: “All legal weapons are limited in the way in which they may be used. Specifically, no weapons may be used indiscriminately.” 
Australia, Law of Armed Conflict, Commanders’ Guide, Australian Defence Force Publication, Operations Series, ADFP 37 Supplement 1 – Interim Edition, 7 March 1994, § 311.
In addition, the Guide states: “Weapons which cannot be directed at military objectives or the effect of which cannot be limited are prohibited.” 
Australia, Law of Armed Conflict, Commanders’ Guide, Australian Defence Force Publication, Operations Series, ADFP 37 Supplement 1 – Interim Edition, 7 March 1994, § 931.
Moreover, the Guide states:
Indiscriminate use is placement of such weapons [i.e. mines, booby traps and other devices] which:
a. is not on, or directed at, a military objective; or
b. employs a method or means of delivery which cannot be directed at a specific military objective; or
c. may be expected to cause incidental loss of civilian life, injury to civilians, damage to civilian objects or a combination thereof, which would be excessive in relation to the concrete and direct military advantage anticipated. 
Australia, Law of Armed Conflict, Commanders’ Guide, Australian Defence Force Publication, Operations Series, ADFP 37 Supplement 1 – Interim Edition, 7 March 1994, § 937.
Australia’s Defence Force Manual (1994) states:
Some weapons and weapons systems are totally prohibited. These blanket prohibitions, which may be traced to treaty or customary international law, are justified on the grounds that the subject weapons are either indiscriminate in their effect or cause unnecessary suffering. 
Australia, Manual on Law of Armed Conflict, Australian Defence Force Publication, Operations Series, ADFP 37 – Interim Edition, 1994, § 304.
The manual also states that poison or poisoned weapons are prohibited “because of their potential to be indiscriminate”. 
Australia, Manual on Law of Armed Conflict, Australian Defence Force Publication, Operations Series, ADFP 37 – Interim Edition, 1994, § 406.
Likewise, according to the manual, “both chemical and biological weapons are prohibited because they cause unnecessary suffering and may affect the civilian population in an indiscriminate fashion”. 
Australia, Manual on Law of Armed Conflict, Australian Defence Force Publication, Operations Series, ADFP 37 – Interim Edition, 1994, § 414.
With respect to weapons deemed to be legal, the manual notes: “All legal weapons are limited in the way in which they may be used. Specifically, no weapons may be used indiscriminately.” 
Australia, Manual on Law of Armed Conflict, Australian Defence Force Publication, Operations Series, ADFP 37 – Interim Edition, 1994, § 415.
Australia’s LOAC Manual (2006) states in its chapter on “Weapons”:
4.4 Some weapons and weapons systems are totally prohibited. These blanket prohibitions, which may be traced to treaty or customary international law, are justified on the grounds that the weapons in question are either indiscriminate in their effect or cause unnecessary suffering.
4.5 It is prohibited to employ weapons which cannot be directed at a specific military objective or the effects of which cannot be limited as required by Additional Protocol I (G.P.I) and are therefore of a nature that they may strike military objectives and civilians or civilian objects without distinction …
4.8 Poison or poisoned weapons are illegal because of their potential to be indiscriminate. …
4.20 … Both chemical and biological weapons are prohibited because they cause unnecessary suffering and may affect the civilian population in an indiscriminate fashion.
4.26 … [I]ndiscriminate use [of anti-vehicle mines] is prohibited.
4.30 All legal weapons are limited in the way in which they may be used. Specifically, no weapons may be used indiscriminately or in such a way as to cause unnecessary injury or suffering. 
Australia, The Manual of the Law of Armed Conflict, Australian Defence Doctrine Publication 06.4, Australian Defence Headquarters, 11 May 2006, §§ 4.4, 4.5, 4.8, 4.20, 4.26 and 4.30.
The LOAC Manual (2006) replaces both the Defence Force Manual (1994) and the Commanders’ Guide (1994).
In 1995, in a statement at the First Review Conference of States Parties to the Convention on Certain Conventional Weapons, the delegation of Australia stated:
Our presence at this conference reflects a shared belief that even the harsh reality of armed conflict should be tempered by humanitarian constraints. Participants in the diplomatic conferences on humanitarian law in the late 1970s concluded that the international community should develop a framework for specific regulations on the use of those conventional weapons which are indiscriminate or disproportionate in their effects. Those weapons have come to include landmines and booby traps, incendiary devices and weapons which injure by means of non-detectable fragments. 
Australia, Statement of 26 September 1995 at the First Review Conference of States Parties to the Convention on Certain Conventional Weapons, Vienna, 25 September–13 October 1995, reprinted in Australian Year Book of International Law, Vol. 16, 1995, p. 732.
In its oral pleadings before the ICJ in the Nuclear Weapons case in 1995, Australia, admitting that “to date, international efforts have not culminated in an international convention banning the threat or use of nuclear weapons in all circumstances”, quoted UN General Assembly Resolution 1653 (XVI) according to which “the use of nuclear and thermo-nuclear weapons would … cause indiscriminate suffering” to conclude that “the use of nuclear weapons would be contrary to international law”. 
Australia, Oral pleadings before the ICJ, Nuclear Weapons case, 30 October 1995, Verbatim Record CR 95/22, pp. 43-44.