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The XM25 Individual Airburst Weapon System: A ‘Game Changer’ for the (Law on the) Battlefield? Revisiting the Legality of Explosive Projectiles under the Law of Armed Conflict

Published online by Cambridge University Press:  30 October 2012

Tom Ruys*
Dr Tom Ruys is Senior Researcher at the Leuven Centre for Global Governance Studies and lawyer at the Brussels Bar (Stibbe). The author wishes to thank Major Johan Gallant (Ballistics Lecturer at the Belgian Royal Military School), Mr Bruno Demeyere, as well as the two anonymous reviewers, for their helpful comments and suggestions. All opinions expressed remain the author's own. Email:
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In the summer of 2010, the US Army began the field-testing of a new weapon, the XM25 ‘Individual Semi-Automatic Airburst System’, which fires ‘airburst’ anti-personnel rounds that can be programmed to detonate at a certain distance. While the XM25 has been heralded as a ‘game changer’ for modern warfare, the question nonetheless remains to what extent it is compatible with the law of armed conflict (LOAC). Against this background, this article aims to examine the legality of the XM25, in particular having regard to the customary prohibition on certain explosive projectiles and the general prohibition on causing superfluous injury and unnecessary suffering.

Copyright © Cambridge University Press and The Faculty of Law, The Hebrew University of Jerusalem 2012

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1 ATK, ‘XM25 Counter Defilade Target Engagement System’, May 2009,

2 ‘XM25 Individual Semi-automatic airburst system (ISAAS)’,

3 See also Dan Whitworth, ‘US Military Unveils “Smart Gun”’, BBC Newsbeat (30 November 2010).

4 ‘Individual Airburst Weapon System (IAWS)’,

5 The current price per bullet is alleged to amount to several hundred dollars (since bullets have to be made by hand at the moment), yet is expected to fall to as low as US$25 once ATK switches to automated production: ‘Magic Bullets: Smart Ammunition is About to Make Things a Lot More Dangerous for Guerrillas Fighting Regular Troops’, The Economist (14 January 2012) (‘Magic Bullets’).

6 ibid; C Todd Lopez, ‘Army Wants 36 More “Punisher” Weapons in 2012’ (8 February 2011),

8 eg, Mark Whittington, ‘XM25 Counter Defilade Target Engagement System Deployed to Afghanistan. “Game Changing” Infantry “Smart” Grenade Launcher’ (1 December 2010),

9 See, eg, ‘Magic Bullets’ (n 5). On the US Army's weapons programme resulting in the development of the XM25 (and its relationship with the XM29 and the XM307), see Anthony G Williams, ‘New Developments in Grenade Ammunition’ (14 November 2010),

10 On the other hand, while ATK has indicated in the past that it was also in the process of developing other types of ammunition for use with the XM25, including armour-piercing rounds that could be used, for example, against lightly armoured vehicles (see ATK, ‘XM25 Counter Defilade Target Engagement System’, May 2009,, the present analysis is concerned exclusively with the high-explosive airburst rounds described above, which are used for anti-personnel purposes and which have no ostensible anti-materiel relevance.

11 Roger S Clark, ‘Methods of Warfare that Cause Unnecessary Suffering or are Inherently Indiscriminate: A Memorial Tribute to Howard Berman’ (1997–98) 28 California Western International Law Journal 379, 385.

12 1868 St Petersburg Declaration Renouncing the Use, in Time of War, of Explosive Projectiles under 400 Grammes Weight, reprinted in Roberts, Adam and Guelff, Richard (eds), Documents on the Laws of War (3rd edn, Oxford University Press 2000) 53Google Scholar.

13 On the prohibition against unnecessary suffering, see, eg, Boothby, William H, Weapons and the Law of Armed Conflict (Oxford University Press 2009) 5568CrossRefGoogle Scholar.

14 Art 23(e), Regulations concerning the Laws and Customs of War on Land, annexed to the Fourth 1907 Hague Convention respecting the Laws and Customs of War on Land (entered into force 26 January 1910) Martens Nouveau Recueil (ser 3) 461. Translation: ‘weapons, projectiles and materials calculated to/of a nature to cause superfluous injury or unnecessary suffering’. On the difference between the non-binding English translations of the 1899 Hague Regulations and the 1907 Hague Regulations, see n 16.

15 First Additional Protocol to the Geneva Conventions and relating to the Protection of Victims of International Armed Conflicts (entered into force 7 December 1979) 1125 UNTS 3 (Additional Protocol I).

16 By pointing at the ‘nature’ of the weapon (as in the non-binding English translation of the 1899 Hague Regulations), rather than it ‘being calculated to’ cause superfluous injury or unnecessary suffering (as in the English translation of the 1907 Hague Regulations), art 35(2) of Additional Protocol I (ibid) makes clear that one should focus on the objective character of the weapon, rather than on the subjective intention of whoever is handling it. See, eg, Dinstein, Yoram, The Conduct of Hostilities under the Law of International Armed Conflict (2nd edn, Cambridge University Press 2010) 64CrossRefGoogle Scholar.

17 Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion [1996] ICJ Rep 266 [35] (Nuclear Weapons) (emphasis added).

18 Dinstein (n 16) 65.

19 Nuclear Weapons (n 17) [35].

20 One, though by no means the only, view found proposes the application of a proportionality test between the foreseeable suffering, on the one hand, and the military advantage intended from the use of a certain weapon or technique, on the other. cf, for example, Oeter, Stefan, ‘Methods and Means of Combat’ in Fleck, Dieter (ed), The Handbook of International Humanitarian Law (Oxford University Press 2008) 130Google Scholar, para 402(2) with Dinstein (n 16) 65: ‘Proportionality … has nothing to do with injury or suffering sustained by combatants’. In any case, it is important not to confuse the arguments regarding the applicability of some sort of proportionality reasoning to determining the legality of weapons as per the SIrUS rule with the principle of proportionality proper, as understood in the law of targeting.

21 UK Ministry of Defence, The Manual of the Law of Armed Conflict (Oxford University Press 2004) 103, para 6.1.5Google Scholar.

22 At the same time, the mere fact that a weapon is subject to a prohibition or restriction in international law, be it customary or conventional, does not necessarily imply that that weapon breaches the superfluous injury principle: Boothby (n 13) 60.

23 cf, as indicated above, art 35(2) of Additional Protocol I (n 15) also mentions that it is prohibited to employ ‘methods of warfare of a nature to cause superfluous injury or unnecessary suffering’.

24 Frits Kalshoven, ‘Arms, Armaments and International Law’ (1985) Recueil des Cours 191, 208.

26 ibid 207–08.

27 The ICRC customary study finds that the Declaration was adhered to by most of the States in existence at that time’: Henckaerts, Jean-Marie and Doswald-Beck, Louise (eds), Customary International Humanitarian Law, vol I: Rules (International Committee of the Red Cross and Cambridge University Press 2009)Google Scholar (ICRC Study I). The United States, however, has objected that it ‘actually represented [the practice] of less than half of the States then in existence’ (see John B Bellinger III and William J Haynes II, ‘A US Government Response to the International Committee of the Red Cross Study Customary International Humanitarian Law’ (2007) 866 International Review of the Red Cross 462) because none of the African or East Asian States in existence at the time acceded to the Declaration.

28 While the exact weight of the 25 mm rounds used with the XM25 is not made public, it may be noted that the weight of the 25 mm rounds used with the XM307 amounted to 132 g (see Williams (n 9)). In light hereof, it is assumed that the rounds used by various individual airburst weapon systems such as the XM25 remain below 400 g.

29 For a discussion of the relevance of ‘verbal’ as compared to ‘physical’ practice, see Ruys, Tom, ‘Armed Attack’ and Article 51 of the UN Charter: Evolutions in Customary Law and Practice (Cambridge University Press 2010) 3144CrossRefGoogle Scholar and the literature cited.

30 Project of an International Declaration concerning the Laws and Customs of War, 27 August 1874, art 13(e); The Laws of War on Land, 9 September 1880, art 9(a) (adopted by the Institute of International Law); Manual of the Laws of Naval War, 9 August 1913, art 16(2) (adopted by the Institute of International Law).

31 Henckaerts, Jean-Marie and Doswald-Beck, Louise (eds), Customary International Humanitarian Law, vol II: Practice (International Committee of the Red Cross and Cambridge University Press 2005)CrossRefGoogle Scholar (ICRC Study II) 1788–90, paras 8–11, 14–18, 24. See also the periodically updated ICRC Customary IHL database, The 400 g limit is explicitly included, inter alia, in Australia's Commanders’ Guide (1994), Australia's Defence Force Manual (1994), Belgium's Law of War Manual (1983), Canada's LOAC Manual (1999 and 2001), Italy's IHL Manual (1991), Ivory Coast's Teaching Manual (2007), New Zealand's Military Manual (1992), the Russian Federation's Military Manual (1990), the Russian Federation's Regulations on the Application of IHL (2001), South Africa's Revised Civic Education Manual (2004), and Spain's LOAC Manual (1996),

32 See ICRC Study II, ibid 1788, para 12.

33 Bellinger III and Haynes II (n 27) 463. As the HPCR Manual on Air and Missile Warfare affirms, the rule of the St Petersburg Declaration has no application to the use of missiles since all missiles exceed the weight limitation: see HPCR, Commentary on the HPCR Manual on International Law Applicable to Air and Missile Warfare, March 2010, 71 (Commentary on the HPCR Manual),

34 See Boothby (n 13) 16.

35 1923 Hague Rules of Aerial Warfare, reprinted in Roberts and Guelff (n 12) 141.

36 See ICRC Study II (n 31) 1788–90, paras 14, 24.

37 ibid 1789, para 18.

38 See ICRC Study I (n 27) 272–73.

39 It is interesting to note that such combined-effects ammunition is explicitly excluded from the scope of the Third Protocol to the Convention on Conventional Weapons. According to art 1(1)(b)(ii) of Protocol III to the Convention on Conventional Weapons (Protocol on Prohibitions or Restrictions on the Use of Incendiary Weapons (1980 Protocol III), reprinted in Roberts and Guelff (eds) (n 12) 533, incendiary weapons do not include ‘[m]unitions designed to combine penetration, blast or fragmentation effects with an additional incendiary effect, such as armour-piercing projectiles, fragmentation shells, explosive bombs and similar combined-effect munitions in which the incendiary effect is not specifically designed to cause burn injury to persons, but to be used against military objectives, such as armoured vehicles, aircraft or facilities’.

40 ICRC Study I (n 27) 272–73.

41 ICRC Study II (n 31) 1789, para 19.

42 Boothby (n 13) 143: ‘Some weapons, including bullets, may sometimes perform in an unusual way and may cause unintended effects. Indeed, any piece of equipment is capable of developing a fault and, as a result, of failing to operate in its usual, designed, or intended manner. Equally, any piece of equipment that is misused, for example in breach of the manufacturer's instructions, will tend as a result to perform in a way which was not intended by the designer, sometimes but not necessarily with damaging consequences’.

43 For an in-depth overview of the controversy (and a critical appraisal of the ICRC's approach), see W Hays Parks, ‘Conventional Weapons and Weapons Reviews’ (2005–8) Yearbook of International Humanitarian Law 57, 90.

44 The 12.7 mm Raufoss round, developed by the Norwegian company Nammo Raufoss, is a (highly popular) multi-purpose projectile weighing circa 43.5 g with an armour-piercing, an explosive, and an incendiary component. It can be used to pierce and explode within lightly armoured targets as well as unarmoured vehicles, and is often used for sniper rifles. See, eg, Hays Parks, ibid 92–93.

45 The ICRC tests (using glycerine soap blocks) were carried out at a time when the Raufoss rounds were already in service with military forces of several nations. The ICRC concluded that when hitting a human body, rather than penetrating the body and exiting on the other side without exploding, the 12.7 mm rounds would often detonate within the human body. If the person hit were to wear body armour, the detonation frequency would be even higher.

46 The ICRC also expressed its concern over the production, sale and use of bullets capable of exploding on impact with a human body before the First Committee of the UN General Assembly in 1998 and 1999. See the quotes in ICRC Study II (n 31) 1793–94, paras 45–46.

47 Thus, it was observed that the Raufoss rounds were not the only ammunition of its kind and, in fact, limited the likelihood of detonation in soft tissue in comparison to previous projectiles. The methodology and correctness of the ICRC's test was also put in doubt, inter alia, because of the short range (100 metres) used for the weapons test, which was said not to correspond with the weapon's intended usage, and because the tissue stimulant used was of greater density than human tissue: see Hays Parks (n 43) 92–95.

48 According to Hays Parks, ibid 95, ‘ICRC representatives and the participating experts in the two experts’ meetings agreed that state practice following promulgation of the St Petersburg Declaration and continuing through the twentieth century had rendered its 400 gram limit obsolete. The government experts agreed with ICRC statements that a munition would be prohibited as constituting superfluous injury were it designed to detonate on impact with soft tissue, i.e., the human body’.

49 ICRC, Statement by Dr Jakob Kellenberger at the 2nd Review Conference of the 1980 Convention on Certain Conventional Weapons, Geneva, 11 December 2001,

50 The ‘dispositif’ of the report is reprinted in ICRC Study II (n 31) 1794, para 47). The report, inter alia,

urged states which produce or transfer explosive projectiles under 400 grams which may explode within the human body urgently to (…) suspend the production and export of such projectiles until they have been adapted so as to ensure that their use against combatants will not contravene the object and purpose of the St Petersburg Declaration. This would involve testing, redesign and other steps to ensure that the chance of the projectile's explosion within the human body (…) has been eliminated.

51 Hays Parks (n 43) 96. Eventually, the Final Declaration adopted at the end of the Review Conference, far from supporting the measures proposed by the ICRC, merely ‘took note’ of the report submitted by the ICRC on the matter, while ‘inviting’ states to consider this report and take appropriate action. No further action was taken. At the Third Review Conference of the CCW Convention, the ICRC raised the matter again, albeit much more cautiously than in 2001:

Repeated ballistic tests [confirm] that these ‘multi-purpose’ bullets can be expected to detonate in the human body under a variety of circumstances, including at short ranges and after striking body armour. We are aware that some States do not share the ICRC's ongoing concerns and that some have sponsored ballistic tests from which they have drawn different conclusions. We are not proposing further action by the Third Review Conference on this matter. Nonetheless, the ICRC invites States, whatever their views on the performance of the ‘multipurpose’ bullet in question, to confirm that they consider, as does the ICRC, that the anti-personnel use of bullets which explode within the human body is prohibited. We also urge States to integrate this rule in their military manuals and other training materials.

ICRC, Statement of Dr Philip Spoerri at the Third Review Conference on the Convention on Certain Conventional Weapons, Geneva, 7 November 2006,

52 Norway, Letter to the President of the ICRC, 11 May 2001, cited in ICRC Study II (n 31) 1791, para 32. (emphasis added).

53 Quoted in ICRC Study II (n 31) 1791, para 35. Furthermore, at the Third Preparatory Committee for the CCW Review Conference in 2001, the US stated that it agreed with the ICRC ‘that there is no valid military requirement for a bullet designed to explode upon impact with the human body’: ibid 1792, para 36.

54 ICRC Study I (n 27) 272–74. Rule 78 holds that ‘[t]he anti-personnel use of bullets which explode within the human body is prohibited’.

55 Bellinger III and Haynes II (n 27) 460 ff.

56 UK Ministry of Defence (n 21) 109.

57 See, however, Secretary-General's Bulletin, Observance by United Nations Forces of International Humanitarian Law, UN Doc ST/SGB/1999/13, 6 August 1999, s 6.2, which prohibits, inter alia, the use of ‘bullets which explode (…) in the human body’.

58 If, because of the delay in ignition, the explosion only occurs 35 cm ‘behind’ the initial surface, this implies that, if the target were a human body, the explosion would take place after the projectile has left the human body.

59 Rather, as explained above, the rounds contain a chip that allows them to track the distance travelled by calculating the number of spiral rotations they make around their axis after leaving the barrel. When the number of spiral rotations corresponds to the programmed distance-to-target, the round will explode.

60 See, however, n 10 above in relation to the development of armour-piercing ammunition for the XM25.

61 n 28.

62 Grenade launchers – which arguably fill the gap between hand grenades and mortars – can come in the form of stand-alone shoulder-fired weapons or attachments mounted under or above the barrel of a rifle. Some grenades are designed to be muzzle-fired. Heavier grenade launchers are typically mounted on vehicles or in emplaced positions.

63 ICRC Study I (n 27) 273.

64 A 1973 ICRC Report distinguishes between explosive and penetrating weapons. Penetrating weapons are said to cause injuries as a result of penetration of the human body by one or more missiles, such as projectiles or fragments. Explosive weapons may cause injury from blast and/or penetration of the human body: see ICRC, ‘Weapons that May Cause Unnecessary Suffering or Have Indiscriminate Effects. Report on the Work of Experts’, Geneva, 1973, paras 41 ff, However, this distinction is not particularly helpful for present purposes.

65 UK Ministry of Defence (n 21) 110, para 6.1.1.

66 US Department of the Army, Field Manual 27–10, ‘The Law of Land Warfare’, 1956, 18.

67 cf Protocol I to the Convention on Conventional Weapons, 1980, reprinted in Roberts and Guelff (eds) (n 12) 527. See also UK Ministry of Defence (n 21) 110.

68 See, in this sense, Kalshoven (n 24) 205–08.

69 ibid 208.

70 As to the legality of the specific use of such weapon against an individual target, see Section 3.

71 Federal Ministry of Defence of the Federal Republic of Germany, ‘Humanitarian Law in Armed Conflicts – Manual’, August 1992, rule 406, (emphasis added).

72 See also Oeter (n 20) 137–38. Oeter explicitly relies on the rule spelt out in the German LOAC Manual. According to Oeter: ‘The basic principle of the [St Petersburg Declaration] has … been transformed [letter/s missing] into customary law as a prohibition of explosive projectiles weighing under 400 g, but into a prohibition against infantry munitions with explosive or inflammable effects’. The present author believes this statement to be correct insofar as ‘infantry munition’ is understood as referring to ‘single enemy’ infantry munition.

According to ICRC Study I (n 27) 272–74, rule 78 applies as a norm of customary law both in international and in non-international armed conflicts. Boothby similarly concludes that the prohibition on the use of certain explosive bullets applies equally in international and non-international armed conflicts: see Boothby (n 13) 326. See, however, Bellinger III and Haynes II (n 27) 465.

73 Translation: ‘He who can do more, can do less’.

74 Whether limitations on certain uses of a particular weapon find their legal basis directly in the SIrUS principle or in a specific customary or conventional rule based on the SIrUS principle is mostly an exercise in semantics. This is particularly the case with regard to limitations on the use of certain explosive projectiles, as both the SIrUS principle and the lex specialis norm concerning particular explosive projectiles (and which is an expression of the SIrUS principle) find their origin in the same document (ie the 1868 St Petersburg Declaration).

75 See, eg, Dinstein (n 16) 65.

76 ICRC Study I (n 27) 272.

77 According to Boothby, it is inappropriate to refer to ‘foreseeability’ as the criterion in this weapons law context. Boothby instead proposes to focus on the ‘usual or normal effect’ of the weapon, since relatively rare and unintended behaviour could in theory be described as ‘foreseeable’: see Boothby (n 13) 144.

78 In a similar vein, see the statement of the ICRC at the Third Review Conference of the CCW, quoted at n 51.

79 Bellinger III and Haynes II (n 27) 460 ff. The US Commentary implicitly interprets rule 78 as proclaiming a general per se prohibition not only of explosive bullets designed for anti-personnel purposes (ibid 461), but also of explosive bullets that have the effect of exploding on impact with the human body (even if designed for anti-materiel purposes). While one may share sympathy with the US criticism of the lack of analytical clarity in the ICRC's position in that rule 78 fails to properly distinguish between the ‘design’ scenario and the ‘effect’ scenario, the US interpretation does not appear to properly reflect the scope of rule 78. Indeed, the better view is that rule 78 merely proscribes the anti-personnel (as opposed to anti-materiel) use of projectiles that have the effect of exploding on impact with the human body (but which are not designed for anti-personnel use), without subjecting them to a per se prohibition. Elsewhere in the ICRC Study, the distinction between the two scenarios is effectively mentioned: ‘The military manuals or statements of several States consider only the anti-personnel use of such projectiles to be prohibited or only if they are designed to explode upon impact with the human body’: ICRC Study I (n 27) 273.

80 Quoted in ICRC Study II (n 31) 1791, para 35 (‘This remains the view of the US’). The broad phrasing (‘that will explode’) would seem to cover both projectiles ‘calculated to’ or ‘designed to’ explode on impact with the human body as well as projectiles ‘of a nature to’ (or ‘the foreseeable effect of which is to’) explode on impact with the human body.

81 ibid 1792, para 40.

82 Reprinted in ICRC Study II, ibid 1792, para 40.

83 HPCR, Manual on International Law Applicable to Air and Missile Warfare, Bern, 15 May 2009, rule 6(e), (emphasis added). At first sight, the rule would appear to exclude both the anti-materiel and the anti-personnel use of such projectiles, thus boiling down to a per se prohibition (and, in fact, going beyond the scope of rule 78 of ICRC Study I). The HPCR Commentary nonetheless clarifies that ‘the prohibition does not affect the use of projectiles against inanimate objects, including aircraft’: see HPCR, Commentary on the HPCR Manual (n 33) 7.

84 UK Ministry of Defence (n 21) 109.

85 See, eg, implicitly Bellinger III and Haynes II (n 27) 463: ‘Although the [ICRC Customary] Study refers to the [Hague Draft Rules of Air Warfare], it does not note that this exception to the total ban on use of exploding bullets permits their use by aircraft without categorical target restrictions, i.e., permits such use for anti-matériel or anti-personnel use’.

86 See ICRC Study II (n 31) 1789, para 18.

87 Commission of Jurists, General Report, reprinted in (1938) 32 American Journal of International Law Supp 1, 20–21: ‘He cannot employ different bullets in accordance with the target at which he is aiming, one sort of ammunition for other aircraft and another sort for land forces by whom he may be attacked. The Commission, therefore, came to the conclusion that the most satisfactory solution of the problem would be to state specifically that the use of tracer, incendiary or explosive projectiles by or against aircraft is not prohibited’.

88 HPCR, Commentary on the HPCR Manual (n 33) 72.

89 Other things being equal, it may be said that casualties from fragmentation weapons are more likely to die than casualties from other types of conventional weapon: see 1973 ICRC Report (n 64), paras 147–51.

90 cf Kalshoven (n 24) 211.

91 The less-than-lethal airburst variant was reported to be a smaller version of the ‘flash bang’ stun grenades popular with special operations and police SWAT teams in hostage situations: see ATK, ‘XM25 Counter Defilade Target Engagement System’ (May 2009), ‘U.S. Army Envisions an XM-25 Smart Gunner in Every Squad from 2014’ Homeland Security News Wire, (13 December 2010),

92 The term ‘non-lethal’ is sometimes criticised since even so-called ‘non-lethal weapons’, such as rubber bullets, can and do cause fatalities in certain situations. Thus, even if these weapons generally minimise fatalities, the danger of fatal injury generally remains: see, eg, Boothby (n 13) 246–47. The UK LOAC Manual (2004) defines non-lethal weapons as ‘weapons that are explicitly designed and developed to incapacitate or repel personnel, with a low probability of fatality or permanent injury, or to disable equipment, with minimal undesired damage or impact to the environment’: UK Ministry of Defence (n 21) 118. See also Koplow, David A, Death by Moderation. The U.S. Military's Quest for Useable Weapons (Cambridge University Press 2010) 203–05Google Scholar.

93 Pictet, Jean, Humanitarian Law and the Protection of War Victims (Sijthoff 1975) 32Google Scholar. This is the so-called ‘Pictet continuum’.

94 ICRC, Interpretive Guidance on the Notion of Direct Participation in Hostilities under International Humanitarian Law (International Committee of the Red Cross 2009) 82.

95 See, eg, the critique of Hays Parks and the reply in Nils Melzer, ‘Keeping the Balance Between Military Necessity and Humanity: A Response to Four Critiques of the ICRC's Interpretive Guidance on the Notion of Direct Participation in Hostilities’ (2010) 42 New York University Journal of International Law and Politics 83.1.

96 ICRC (n 94) 78–82. The document acknowledges that ‘[d]uring the expert meetings, it was generally recognized that the approach proposed by Pictet is unlikely to be operable in classic battlefield situations involving large-scale confrontations … and that armed forces operating in situations of armed conflict, even if equipped with sophisticated weaponry and means of observation, may not always have the means or opportunity to capture rather than kill’ (82, fn 221; see also 78, fn 212). For this reason, the use of non-lethal weapons is thought to be ‘particularly relevant where a party to the conflict exercises effective territorial control, most notably in occupied territories and non-international armed conflicts’ (81). The document acknowledges that ‘[i]n classic large-scale confrontations between well-equipped and organized armed forces or groups, the principles of military necessity and of humanity are unlikely to restrict the use of force against legitimate military targets beyond what is already required by specific provisions of IHL’.

97 NATO Policy on Non-Lethal Weapons, 1999, RTO-TR-SAS-040, Annex B, B-1, The UK LOAC Manual (2004) states that ‘[g]enerally speaking, devices that temporarily incapacitate combatants … are, from the lethal point of view, to be preferred to lethal weapons or those that cause permanent harm to individuals’: UK Ministry of Defence (n 21) 118.

98 See Boothby (n 13) 78.

99 Dinstein (n 16) 127–28.

100 Michael N Schmitt, ‘Future War and the Principle of Discrimination’ (1998) 28 Israel Yearbook on Human Rights 51, 55.

101 ibid.

102 See, eg, Rogers, APV, ‘The Principle of Proportionality’ in Hensel, HM (ed), The Legitimate Use of Military Force (Ashgate 2007) 189Google Scholar; Friedhelm Krüger-Sprengel, ‘Le concept de proportionalité dans le droit de la guerre’ (1980) 19 Revue de Droit Militaire et de Droit de la Guerre 177; Frits Kalshoven, ‘Implementing Limitations on the Use of Force: The Doctrine of Proportionality and Necessity’ (1992) 86 American Society of International Law Proceedings 39; Michael N Schmitt, ‘The Principle of Discrimination in 21st Century Warfare’ (1999) 2 Yale Human Rights and Development Law Journal 143.

103 cf Dinstein (n 16) 127.

104 Leaving aside the discussion on (voluntary or involuntary) human shields.

105 Thus, many IHL handbooks simply restate the content of the St Petersburg Declaration without further ado: eg, Kolb, Robert, Ius in Bello. Le droit des conflits armés (2nd edn, Bruylant 2009) 297Google Scholar. David even seems to negate the erosion of the St Petersburg Declaration through subsequent customary practice: see David, Eric, Principes de droit des conflits armés (4th edn, Bruylant 2008) 372–73Google Scholar (‘ce n'est pas parce qu'il existe une pratique contraire à une règle qu'il en découle nécessairement une nouvelle règle coutumière’: ‘it's not because there exists a practice that is contrary to a rule that this necessarily gives rise to a new customary rule’). For some examples of articles focusing on the legality of (specific types of) small arms ammunitions under the law of armed conflict, see, eg, Mark G Granat, ‘Modern Small-Arms Ammunition in International Law’ (1993) 40 Netherlands International Law Review 149; W Hays Parks, ‘Means and Methods of Warfare’ (2006) 38 George Washington International Law Review 511; Robin Coupland and Dominique Loye, ‘The 1899 Hague Declaration Concerning Expanding Bullets. A Treaty Effective for More than 100 Years Faces Complex Contemporary Issues’ (2003) 849 International Review of the Red Cross 135.

106 Hays Parks (n 43) 100–01. See also, in relation to expanding bullets, Coupland and Loye, ibid.

107 According to art 36 of Additional Protocol 1 (n 15): ‘In the study, development, acquisition or adoption of a new weapon, means or method of warfare, a High Contracting Party is under an obligation to determine whether its employment would, in some or all circumstances, be prohibited by this Protocol or by any other rule of international law applicable to the High Contracting Party.’

108 n 47.

109 On a general note, it may be said that the legality of small arms ammunition is a field which the ICRC has found difficult to enter. Ever since this topic appeared on the ICRC's radar (in the wake of the Vietnam War), it has struggled to overcome states’ reluctance to put this on the international agenda. This is reflected not only in the Raufoss saga (cf Hays Parks (n 43)), but also in the criticism in respect of the ICRC's 1973 report on weapons that may cause unnecessary suffering (n 64) (cf Hays Parks (n 105) 515) as well as the premature conclusion of the ICRC's SIrUS project (see, eg, Boothby (n 13) 65–66). One might add that the ICRC has also adopted a guide on the review of new weapons in accordance with art 36 of Additional Protocol I (ICRC, ‘A Guide to the Legal Review of New Weapons, Means and Methods of Warfare: Measures to Implement Article 36 of Additional Protocol I of 1997’ (January 2006, revised November 2006, 13–14 and 16), Unfortunately, however, today most states, whether party to Additional Protocol I or not, still lack such a mechanism for the legal review of new weapons, means or methods of warfare.

110 Lopez (n 6).