Rule 43. Application of General Principles on the Conduct of Hostilities to the Natural Environment
Rule 43. The general principles on the conduct of hostilities apply to the natural environment:
Summary
State practice establishes this rule as a norm of customary international law applicable in both international and non-international armed conflicts.
Principle of distinction
The rule that it is prohibited to attack any part of the natural environment unless it is a military objective is based on the general requirement that a distinction be made between military objectives and civilian objects (see Rule 7). This rule is reflected in Protocol III to the Convention on Certain Conventional Weapons, which provides that “it is prohibited to make forests or other kinds of plant cover the object of attack by incendiary weapons except when such natural elements are used to cover, conceal or camouflage combatants or other military objectives, or are themselves military objectives”.[1]  The military manuals and official statements which consider that an area of land may be a military objective if it meets the required conditions also reflect this.[2] 
The application of the principle of distinction to the natural environment is set forth in the Guidelines on the Protection of the Environment in Times of Armed Conflict.[3]  The UN General Assembly has invited all States to disseminate these Guidelines widely and to give due consideration to the possibility of incorporating them into their military manuals and other instructions addressed to their military personnel.[4]  The application of the principle of distinction to the natural environment is also supported by military manuals and official statements.[5]  The Final Declaration adopted by the International Conference for the Protection of War Victims in 1993 urged States to reaffirm and ensure respect for international humanitarian law protecting the natural environment against “attacks on the environment as such”.[6] 
The principle of distinction, which is applicable in international and non-international armed conflicts (see Rule 7), applies equally in relation to the environment. The ICRC made such a statement of principle in 1993 in a report submitted to the UN General Assembly on the protection of the environment in time of armed conflict.[7]  This assertion was uncontested.
Destruction of property not justified by military necessity
According to State practice, the prohibition on destroying or seizing the property of an adversary, unless required by imperative military necessity (see Rule 50) applies equally to the natural environment. The applicability of this prohibition to the natural environment is set forth in the Guidelines on the Protection of the Environment in Times of Armed Conflict.[8]  This is supported by military manuals, national legislation and official statements.[9] 
In its advisory opinion in the Nuclear Weapons case in 1996, the International Court of Justice stated that “respect for the environment is one of the elements that go to assessing whether an action is in conformity with the principle of necessity”.[10]  The Committee Established to Review the NATO Bombing Campaign Against the Federal Republic of Yugoslavia was of the view that the environmental impact of that bombing campaign was “best considered from the underlying principles of the law of armed conflicts such as necessity and proportionality”.[11] 
Furthermore, under the Fourth Geneva Convention, extensive destruction of property “not justified by military necessity and carried out unlawfully and wantonly” constitutes a grave breach.[12]  This rule is restated in other instruments with respect to the natural environment.[13]  It is also applied to the natural environment in a number of official statements.[14]  In a resolution on the protection of the environment in times of armed conflict in 1992, the UN General Assembly stressed that “destruction of the environment, not justified by military necessity and carried out wantonly, is clearly contrary to existing international law”.[15]  The Final Declaration adopted by the International Conference for the Protection of War Victims in 1993 urged States to reaffirm and ensure respect for international humanitarian law protecting the natural environment against “wanton destruction causing serious environmental damage”.[16] 
The prohibition of unnecessary destruction of property is applicable in international and non-international armed conflicts (see Rule 50) also in relation to the environment. The ICRC made such a statement of principle in 1993 in a report submitted to the UN General Assembly on the protection of the environment in time of armed conflict.[17]  This assertion was uncontested.
Principle of proportionality
Practice shows a general acceptance of the principle that incidental damage affecting the natural environment must not be excessive in relation to the military advantage anticipated from an attack on a military objective. This is set forth in the Guidelines on the Protection of the Environment in Times of Armed Conflict and in the San Remo Manual on Naval Warfare.[18] 
The applicability of the principle of proportionality to incidental damage to the environment is supported by a number of official statements.[19]  During the bombing campaign against the Federal Republic of Yugoslavia, NATO stated that, when making targeting decisions, it took into account “all possible collateral damage, be it environmental, human or to the civilian infrastructure”.[20]  The Committee Established to Review the NATO Bombing Campaign Against the Federal Republic of Yugoslavia was of the view that the environmental impact of that bombing campaign was “best considered from the underlying principles of the law of armed conflicts such as necessity and proportionality” and stated that “in order to satisfy the requirement of proportionality, attacks against military targets which are known or can reasonably be assumed to cause grave environmental harm may need to confer a very substantial military advantage in order to be considered legitimate”.[21] 
In its advisory opinion in the Nuclear Weapons case in 1996, the International Court of Justice stated that “States must take environmental considerations into account when assessing what is necessary and proportionate in the pursuit of legitimate military objectives”.[22] 
The principle of proportionality is applicable in both international and non-international armed conflicts (see Rule 14) also in relation to the environment. The ICRC made such a statement of principle in 1993 in a report submitted to the UN General Assembly on the protection of the environment in time of armed conflict.[23]  This assertion was uncontested.
Other rules affording protection to the natural environment
A number of other rules of international humanitarian law have the effect of preventing or limiting damage to the environment, even though they were not developed for this purpose, but rather for the purpose of protecting the civilian population. Examples of such rules include the obligation to take particular care when works and installations containing dangerous forces which are military objectives are made the object of an attack (see Rule 42) and the prohibition on attacking objects indispensable to the survival of the civilian population (see Rule 54). Belligerent reprisals against the natural environment are discussed in Chapter 41.

[1] Protocol III to the Convention on Certain Conventional Weapons, Article 2(4) (cited in Vol. II, Ch. 30, § 110).
[2] See, e.g., the statements of Belgium (cited in Vol. II, Ch. 2, § 622), Canada (ibid., §§ 597 and 623), Federal Republic of Germany (ibid., §§ 597 and 624), France (ibid., § 598), Italy (ibid., § 597), Netherlands (ibid., §§ 597, 599 and 625), New Zealand (ibid., § 597), Pakistan (ibid., § 599), Spain (ibid., § 597), United Kingdom (ibid., §§ 597, 599 and 626) and United States (ibid., §§ 599 and 627–628) and the military manuals of Australia (ibid., § 601), Belgium (ibid., §§ 602–604), Benin (ibid., § 605), Ecuador (ibid., § 608), France (ibid., § 609), Italy (ibid., §§ 610–611), Madagascar (ibid., § 612), Netherlands (ibid., § 613), New Zealand (ibid., § 614), Spain (ibid., § 615), Sweden (ibid., § 616), Togo (ibid., § 617), United Kingdom (ibid., § 618) and United States (ibid., § 619).
[3] Guidelines on the Protection of the Environment in Times of Armed Conflict, § 4 (cited in Vol. II, Ch. 14, § 5).
[4] UN General Assembly, Res. 49/50 (adopted by consensus) (ibid., § 56); see also Res. 51/157, Annex (ibid., § 57).
[5] See, e.g., Australia, Defence Force Manual (ibid., § 8); the statements of Canada (ibid., § 37), Islamic Republic of Iran (ibid., § 41), Marshall Islands (ibid., § 45), Russian Federation (ibid., § 47) and United States (ibid., §§ 50 and 53).
[6] International Conference for the Protection of War Victims, Final Declaration (ibid., § 61).
[7] ICRC, Report on the protection of the environment in time of armed conflict (ibid., § 67).
[8] Guidelines on the Protection of the Environment in Times of Armed Conflict, §§ 8 and 9 (ibid., § 5).
[9] See, e.g., the military manuals of Australia (ibid., § 8) and United States (ibid., § 11), the legislation of Nicaragua (ibid., § 22) and Spain (ibid., § 25) and the statements of Australia (ibid., § 30), Austria (ibid., § 33), Canada (ibid., § 36), Islamic Republic of Iran (ibid., §§ 41–42) and United States (ibid., §§ 50 and 52–53); see also Report of an expert meeting on the protection of the environment in time of armed conflict (ibid., § 60).
[10] ICJ, Nuclear Weapons case, Advisory Opinion (ibid., § 62).
[11] Committee Established to Review the NATO Bombing Campaign Against the Federal Republic of Yugoslavia, Final Report (ibid., § 63).
[12] Fourth Geneva Convention, Article 147 (cited in Vol. II, Ch. 16, § 53).
[13] See, e.g., Agenda 21, § 39.6 (cited in Vol. II, Ch. 14, § 3); San Remo Manual, § 44 (ibid., § 4); Guidelines on the Protection of the Environment in Times of Armed Conflict, § 8 (ibid., § 5).
[14] See, e.g., the statements of Brazil (ibid., § 35), Islamic Republic of Iran (ibid., § 41) and United States (ibid., §§ 50 and 52); see also the statements of Japan (“destruction of the environment”) (ibid., § 43), Sweden (destruction “on an unprecedented scale”) (ibid., § 48) and United Kingdom (“a deliberate crime against the planet”) (ibid., § 49).
[15] UN General Assembly, Res. 47/37 (adopted without a vote) (ibid., § 55).
[16] International Conference for the Protection of War Victims, Final Declaration (ibid., § 61).
[17] ICRC, Report on the protection of the environment in time of armed conflict (ibid., § 67).
[18] Guidelines on the Protection of the Environment in Times of Armed Conflict, § 4 (ibid., § 5); San Remo Manual, § 13(c) (ibid., § 6).
[19] See the statements of Australia (ibid., § 30), Austria (ibid., § 34), Canada (ibid., § 37), Colombia (ibid., § 39), Islamic Republic of Iran (ibid., § 41), Jordan (ibid., § 44), Romania (ibid., § 46) and United States (ibid. , §§ 44 and 50); see also Report of an expert meeting on the protection of the environment in time of armed conflict (ibid., § 60).
[20] See the reported practice of NATO (ibid., § 58).
[21] Committee Established to Review the NATO Bombing Campaign Against the Federal Republic of Yugoslavia, Final Report (ibid., § 63).
[22] ICJ, Nuclear Weapons case, Advisory Opinion (ibid., § 62).
[23] ICRC, Report on the protection of the environment in time of armed conflict (ibid., § 67).