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Rules Regulating the Conduct of Hostilities

Paper Type: Free Essay Subject: Law
Wordcount: 6392 words Published: 23rd Sep 2019

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Origins and definition

The rules regulating the conduct of hostilities are central to the framework of international humanitarian law (IHL). The principles of distinction, proportionality and precaution establish the parameters by which the adversaries must conduct their military operations. This essay seeks to examine the theoretical and practical aspects of the principle of distinction.

At the heart of IHL protection framework is the principle of distinction, which is codified in article 48 of the 1977 Additional Protocol I to the Geneva Conventions of 1949 (AP I).[1] Parties to the conflict must at all times distinguish between civilians, who have a presumption of inoffensiveness and combatants, who are lawful subjects of attack and also between civilian objects and military targets. Operations may be directed only against military objectives and combatants.[2]

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The principle was expressed as early as 1868 in the Preamble to St. Petersburg Declaration,[3] and was later incorporated into the Regulations annexed to the 1907 Hague Convention Respecting the Laws and Customs of War on Land.[4] The contemporary rules on distinction are contained in the Geneva Conventions 1949[5] and their Additional Protocols which create an extensive legal framework regulating modern armed conflicts.[6] Besides being firmly incorporated into treaties, the principle forms part of international customary law which binds all states even those not parties to the conventions.[7]  

The principle is also enshrined in numerous military manualsand national legislations. Moreover, violations of the principle were condemned in numerous resolutions of the Security Council. [8]


When making a targeting decision, all of the three principles are involved. The principle of proportionality requires that civilian losses from a military action should not be excessive in relation to the expected military advantage.[9] If the planners decide that the targeting is a military object, the scope of potential loss of civilian lives must be mapped. This highlights the importance of assessing the nature of the attack and other relating factors such as the magnitude of damage and the type of weaponry used.

Proportionality decision fits into the targeting process only after a commander has ensured that a distinction between, on one hand, protected objects and persons and legitimate military targets on the other. Conducting a proportionality assessment is legally relevant is only when civilians or civilian objects might be affected by the proposed attack. It therefore does not apply to attacks that will only affect combatants or military objects.[10]

Lastly, is the principle of precautions which comprises a series of requirements relating to the lawful means the methods applicable to attacking a lawful target.[11] The obligation in art 57 (2) (a)(i) relating to target identification is the most relevant to the applicability of distinction in conflict zone. Commanders are required do everything feasible (available intelligence) to verify whether a certain objective is a civilian or civilian object, and thus could not be targeted under the principle of distinction.[12] Verification is complementary to the legal assessment conducted under distinction. In other words, the first step in a precaution analysis is to refer to the legal interpretation on what constitutes a military target, then apply all available information to that standard of interpretation before launching an attack.


AP I applicable to international armed conflicts (‘IAC’) sets out concrete obligations derived from the general principle of distinction under Article 48 AP I.

First, is in relation to persons. Only combatant of the adversary party can be made the object of attack, while the civilian population and other protected persons and objects may not be. Individual civilians may only be attacked if and for such time as they directly participate in hostilities.[13]

The targeting framework applicable in IAC’s is constructed on the understanding that individuals can be divided into combatants and civilians. The protection afforded under this protocol is determined by the category to which an individual belongs. Civilians are defined those who are not combatants.[14] Combatant-status confers immunity from criminal prosecution for war acts conducted in accordance with IHL. This includes the lawful killing or wounding of an enemy combatant, which would ordinarily be a violation of domestic law.[15] Moreover, combatants are entitled, upon capture by enemy forces, to treatment as prisoners of war.

During a military engagement, combatant are expected to distinguish themselves from the civilian population by wearing a military uniform or other distinctive signs.[16] The rationale is to protect civilians from being mistakenly identified as a legitimate target.

Furthermore, the mere presence of persons falling outside the definition civilians within the civilian population, shall not deprive it from its civilian character.[17] Where any doubt arises as to the status of a person, that person shall be presumed to be civilian.[18] The protocol mentioned specific prohibitions including the prohibitions of acts of violence that specifically terrorise the civilian population. Similarly, indiscriminate attacks using methods or means of combat which cannot be directed at military objects or whose effects cannot be limited in time or space are prohibited.[19]

Second, civilian objects, this is to say, all objects which do not come under the definition of military objects are protected against attacks. Further, article 52(2) AP I reaffirms the obligation of the parties to the conflict to limit their attacks strictly against military objectives. The applicable test is that the objects contribution to the military operation must be ‘effective’ by virtue of their nature, location, purpose or use and the military advantage of their destruction must be ‘definite’. 

At the conventional level, it is accepted that NIAC’s, which occur between state armed forces and non-state armed groups or between such groups themselves, are regulated by Common Article 3 to the Four Geneva Conventions (CA 3) and AP II. CA 3 provides a minimum protection to those “not taking direct part in hostilities”. AP II strengthens civilian protection beyond the minimum standards contained in CA 3 by including the prohibition against attacking civilians and acts of terrorism.

These provisions on the principle of distinction and their implications are part of customary law. thus, they apply in both conflicts and binds states that are not party to the treaty, such as Israel and the United States.[20]


There are various mechanisms that have been adopted to strengthen compliance with IHL. One of which can take the form of individual criminal responsibility.

The principle was first recognised in the Charter of the International Military (‘IMT’).[21] This recognition has made it possible to prosecute and punish individuals for war crimes of IHL. The Nuremberg precedent also created other important principles aimed at ensuring individual accountability for war crimes. It emphasised the exclusion of the official position of an individual or the mere existence of superior orders, as valid grounds for relieving an individual of responsibility for such crimes.[22]

The Rome Statute of the International Criminal Court (‘ICC’) reinforced the principle of criminal responsibility over persons who committed war crimes.[23] The definition of war crimes incorporates the grave beaches systems as well as other “serious violations of the laws and customs” committed in the context of IAC’s.

Directing attacks against civilians or civilian objects is considered a war crime when committed with intent and knowledge of the circumstances of an armed conflict.[24]

Article 17 of the Statute highlights that the ICC’s role is complementary to states national legal systems. In other words, the Court exercises its jurisdiction over war crimes in limited circumstances where the prosecuting state is unwilling or unable to prosecute and investigate these crimes

The concept of war crimes can be derived from grave breaches committed against persons and objects designated protected under the Conventions and AP I. [25]

States parties to the conventions are assumed the obligation to search for, prosecute and punish perpetrators of these grave breaches in their own countries, by incorporating into their national criminal law the provisions necessary for the prosecution and punishment of the perpetrators of international crimes or to hand that person over for trial in another State.[26]

All grave breaches of the Conventions and the Protocol are war crimes.[27] War crimes and grave breaches are equally a violation of a rule of IHL. However, criminal consequences of grave breaches are limited to the domestic sphere.

States criminal laws generally apply only to crimes committed on their territory or by their own nationals, however, numerous states such as New Zealand[28] and Canada[29] have incorporated the list of war crimes contained in the Statute to prosecute perpetrators of war crimes irrespective of their nationality or where the they were committed. This principle is known as “universal jurisdiction”.[30]

Whereas most of the convictions of high-ranking German commanders during the Nuremberg trials were based on positive acts of the superiors, superiors can be held responsible for war crimes committed by their subordinates where they fail to meet their duty of taking preventative measures ahead of a crime or to punish those responsible afterwards.[31]

In the context of NIAC’s, CA 3 and AP II do not make any reference of any enforcement measures of criminal responsibility. However, the Appeals Chamber in the Tadic case disregarded the dichotomy between both IAC and NIAC. It stated that serious violations of CA 3 entail individual criminal responsibility under customary international law.[32] However, not every violation of IHL amounts to war crimes. The Tribunal provided preconditions that must be met in order to comply with war crimes. The violation must breach a primary rule of IHL that is provided by a treat or customary law; the violation must under either treaty or customary law entail criminal responsibility for those violating the rule.[33] Individual responsibility for violating the rules in CA 3 and AP II are also recognised in the under Statute of the International Tribunal for the Former Yugoslavia Statute[34], the International Tribunal for Rwanda[35] and the ICC Statute[36].

It is debatable whether giving war crimes status to crimes committed in NIACs’ universal allow for their prosecution on the basis of universal jurisdiction. Neither CA3 nor AP II provide for such. The ratification of the Rome Statute does not grant states universal jurisdiction in relation to these crimes. Nevertheless, Belgium’s 1993 allowed for the prosecution of serious violation in NIAC’s on this basis. However, following the 2003 intervention in Iraq, the U.S expressed concerns that incorporating of the principle into Belgium’s national law might lead to the prosecution of U.S military and political leaders. In response to threats over moving the NATO headquarters, the 1993 law was repealed. Arguably, political pressure may be a set-back to the enforcement of IHL.

Problems: Membership in Organised Armed Groups

NIACs’ represent the majority of armed conflicts in today’s world.[37] It is well known that for there to be a NIAC, the violence must involve an organised armed group whose members often fail to distinguish themselves from the civilian population. This has the potential to undermine the civilian protection due to erroneous conclusions that they are also members of an armed group.[38] This entails a question of how one should determine membership in such groups for the purpose of targeting in IHL.

Generally speaking, the term “organised armed groups” is not defined in treaties, despite being crucial for the existence of an NIAC. In IAC, the term usually comprises irregular armed forces belonging to a state (militias, volunteer corps and organized resistance groups).[39] However, in NIAC’s, art 1(1) AP II implies that the term refers to groups acting as the armed forces of a non-state party to an armed conflict. 

Sandesh concludes that organised armed groups can be categorised along two lines. The first is the vertical structure, with a defined chain of command.This includes most “traditional groups” such as Hezbollah in Lebanon or Tamil Tigers (LTTE) in Sri Lanka which have a state army-like military structure and clear distinctive uniforms, that allow immediate visual identification.[40]

The second set of groups is more complex. They are structured horizontally with the control and initiation of operative activities being distributed across all members. Thus, leadership is attributed with providing fundamental ideology and objectives more than clear orders or military command. For example, the forces of the Taliban of Afghanistan, during their conflict with the International Security Assistance Force (ISAF), were described as lacking organised uniformed military structure or decision-making power. They had great fluctuations in their functioning and often resorted to guerrilla tactics as part of their operations.[41]

The complexity arises in ascertaining whether or not a person is considered a member an organised group. Membership is absent from the relevant treaty provisions. In order to establish a link between an individual and a party to a conflict, the traditional rules of IHL relied on formal membership manifested by the wearing of military uniforms, the display of fixed emblems recognisable at a distance and the carrying of arms openly.[42] Consequently, the link is easily administered for both sides of a conflict without the need for further investigations. Thus, there is little ambiguity about the notion in regular forces.

However, the application of formal membership may not map on the loose structures of contemporary groups like the Taliban, which demonstrate none of these features that IHL typically assigns to state armed forces. Difficulties in determining membership particularly arose during the conflict in Afghanistan. One famous incident was when German forces in the North Atlantic Treaty Organization (NATO) targeted tanker trucks which had been seized by the Taliban fighters near Kunduz. The strike resulted in the killing of at least 30 civilians who were surrounding the truck. Germany’s Defence Ministry claimed ambiguity as to whether those individuals were of the Taliban group.[43]

Alternatively, the ICRC proposed that membership should be attached only to individuals whose continuous combat function (‘CCF’) is to participate in hostilities.[44] Function requires “lasting integration” into the group as opposed to the more transitory.[45] The rationale of functional membership is distinguish between, on one hand, individuals whose continuous function involves the preparation, execution, or commands of attacks, and others who may be directly participate in hostilities, but on a spontaneous or unorganized level, or who assume exclusively political, administrative or other non-combat functions.[46]

lose protection from attack for such time.[47] individuals who support a particular group, including recruiters and trainers, but whose function does not involve direct participation in hostilities are excluded.[48]

With the assumption that conceptualising the notion as proposed by the ICRC is to be accepted, the absence of factual criteria allowing states or other actors to determine in practice that a person in the adversary party is assuming a particular function remains an issue. For example, Melzer proposes that CCF may be identified on the basis of “conclusive behaviour” by means of repeated DPH.[49] However, professor Schmitt is critical of the practical applicability of the approach. He argued if an individual is positively identified having directly participated in hostilities on a previous occasion, how can the adversary know whether that was a periodic engagement or that the individual assumes CCF in an operation conducted on behalf of an organised group and? This is particularly problematic in critical situations that requires a combatant to act in self-defence and make an instant decision on whether or not the attacking party is a legitimate target.[50]

Some scholars disapproved of the membership-oriented nature of the concept and believed it creates a requirement that provides an unfair and unwarranted advantage to these groups. For example, Watkin and Schmitt criticised that all members of state armed forces would be vulnerable to attacks on continuous basis, even those performing administrative or logistic functions, irrespective of their direct participation in hostilities. By contrast, only members of non-state armed groups assuming continuous combat function can be lawfully targeted.[51]

Contradicting the Guidance is the extensive view, which Schmitt states it equalises standards across both state and non-state groups. This view is supported by state practice. The U.S and most of NATO states in their military operations against the Islamic State identified all members, including those in roles not involving direct participation in hostilities.[52]

However, enforcing a standard treatment to all armed forces cannot be reconciled with the existing treaty law which holds that membership in state armed forces to be based not on fictional criteria, but primarily on formal integration into uniformed armed units in accordance with domestic law. whereas integration into state armed forces depends on a formal enrolment, integration into these groups is derived from various degrees of affiliations.[53]

If implemented, the concept may be more practical, yet it will require resourceful intelligence to gain knowledge about the internal structure and hierarchy of all organised armed group in an armed conflict. Melzer cautions that a permissive approach that is solely driven by military necessities, disregarding humanity considerations would result in an unjustifiable level of arbitrary targeting of civilians.[54]

It is estimated that civilian deaths from the Coalition airstrikes against ISIS are between 7,357–11,745.[55] It is concerning that membership would not be the result of a legal appreciation, but rather, dependent on armed groups’ apprehension of the notion. This would invite excessively broad targeting measures that are susceptible to error and abuse. It is concerning that the notion of “association” with terrorist groups, broadly used in states criminal law and the United Nations counterterrorism sanctions, may be indiscriminately transposed into IHL, thus undermining the importance of the application of the principle of distinction.


Membership in NIAC’s is a complex area. The notion needs to be carefully framed and delimited as to establish a balance between military and humanity necessities. The previous interpretations of the concept are useful, however, remain insufficient. They should be complemented by a legal analysis of the notion that accommodates the structure and function of contemporary groups. Analyse and comparing the practice of several states is useful to understand how they determine the existence of an organized armed group and, most importantly, how they establish membership in such groups. A solid legal foundation ensures that the key legal terms are left prone to state’s political agendas and security justifications.


Primary sources




International Crimes and International Criminal Court Act 2000 (NZ)

Crimes Against Humanity and War Crimes Act 2000 (CA)

Declaration Renouncing the Use, in Time of War, of Explosive Projectiles Under 400 Grammes Weight (adopted 11 December 1868, entered into force 11 December 1868) 58 BFSP 16 (St. Petersburg Declaration)

Regulations annexed to the 1907 Hague Convention Respecting the Laws and Customs of War on Land (adopted 18 October 1907, entered into force 26 January 1910) 2277 UNTS 539

Protocol Additional to the Geneva Conventions, and relating to the Protection of Victims of Non-International Armed Conflicts (Protocol II) (8 June 1977) 1125 UNTS 609

Protocol Additional to the Geneva Conventions, and relating to the Protection of Victims of Non-International Armed Conflicts (Protocol I), 8 June 1977, 1125 UNTS 3

Declaration Renouncing the Use, in Time of War, of Explosive Projectiles Under 400 Grammes Weight (adopted 11 December 1868, entered into force 11 December 1868) 58 BFSP 16 (St. Petersburg Declaration)

Convention (I) for the Amelioration of the Condition of the Wounded and Sick in Armed Forces in the Field (adopted 12 August 1949, entered into force 21 October 1950) 75 U.N.T.S 31

Convention (II) for the Amelioration of the Condition of Wounded, Sick and Shipwrecked Members of Armed Forces at Sea (adopted 12 August 1949, entered into force 21 October 1950) 75 U.N.T.S 85

Convention (III) relative to the Treatment of Prisoners of War (adopted 12 August 1949, entered into force 21 October 1950) 75 U.N.T.S. 135

The Charter of the International Military Tribunal – Annex to the Agreement for the prosecution and punishment of the major war criminals of the European Axis (signed 8 August 1945, entered into force 8 August 1945) 82 UNTS 279

Convention (IV) relative to the Protection of Civilian Persons in Time of War (adopted 12 August 1949, entered into force 21 October 1950) 75 U.N.T.S. 287

Rome Statute of the International Criminal Court (adopted 17 July 1998, entered into force 1 July 2002) 2187 U.N.T.S. 90



  • Prosecutor v Tadić (Interlocutory Appeal Decision) ICTY-94–1-AR72 (2 October 1995)
  • Legality of the Threat or Use of Nuclear Weapons (Advisory Opinion) [1996] ICJ Rep 226

Secondary sources



  • Ian Henderson,The Contemporary Law of Targeting Military Objectives, Proportionality and Precautions in Attack under Additional Protocol I (Brill, 2009)
  • Henckaerts J and Doswald-Beck L, Customary International Humanitarian Law Volume I: Rules (Cambridge University Press, 2005)
  • Melzer N, Interpretive Guidance on the Notion of Direct Participation in Hostilities under International Humanitarian Law (International Committee of the Red Cross, 2009)
  • Sivakumara S, The Law of Non-International Armed Conflict (Oxford, 2012)

Journal articles

  • Sivakumara S, ‘Re-envisaging the International Law of Internal Armed Conflicts’ (2011) 22 EJIL 219
  • Schmitt M N, ‘The Interpretative Guidance on Direct Participation in Hostilities: A Critical Analysis’, (2010) 1 HNSJ 5
  • Whittemore L A, ‘Proportionality Decision Making in Targeting:  Heuristics, Cognitive Biases, and the Law’ (2009) 7 NSJ 577
  • Schmitt M N, ‘The Interpretative Guidance on Direct Participation in Hostilities: A Critical Analysis’, (2010) 1 HNSJ 5
  • Watkin K, ‘Opportunity Lost: Organized Armed Groups and the ICRC “Direct Participation in Hostilities” Interpretive Guidance’ (2012) 42 N.Y.U. J. INT’L L. & POL 641
  • Huston P, ‘A Practical Perspective on Attacking Armed Groups’ (2018) 51 VJTL 919
  • Melzer N, ‘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 NYU J. Int’l L. & Pol 831

Newspaper articles


Official materials

  • United Nations Security Council (UNSC) Res 827 (25 May 1993) UN Doc S/RES/827
  • United Nations Security Council (UNSC) Res 955 (8 November 1994) UN Doc S/RES/955
  • United Nations Security Council (UNSC) Res 564 (31 May 1985) UN Doc S/Res/564
  • United Nations Security Council (UNSC) Res 771 (13 August 1992) UN Doc S/Res/771


[7] Legality of the Threat or Use of Nuclear Weapons (Advisory Opinion) [1996] ICJ Rep 226.

[9] AP I, art 51 (5)(b); Henckaerts (n 2) 46.

[11] AP I, art 57.

[12] Ian Henderson,The Contemporary Law of Targeting Military Objectives, Proportionality and Precautions in Attack under Additional Protocol I (Brill, 2009) 161-165.

[13] AP I, art 51 (3); CIHL, rule 6.

[14] AP I, art. 50; AP I, art 43 (1); Geneva Conventions (III), art 4 (A)(1) (2).

[15] Geneva Conventions (III), art 4 (A)(2).

[16] AP I, art 44 (3)

[17] AP I, art 50 (3).

[18] AP I, art 50 (1)

[19] AP I, art 51 (4); Prosecutor v Martić (Judgment) ICTY-95-11 (12 June 2007) [463].

[20] Henckaerts (n 2).

[22] Ibid arts 7, 8.

[24] Ibid art 8 (2)(a)(b), art 30.

[25] GC I art 50; GC II art 51; GC III, art 130; GC IV, art 147; AP I, art 85; AP I, art 86; AP I, art 11 (4).

[26] GC I, arts 49; GC II, art 50; GC III, art 129; GC IV, art 146; ICHL, rule 158.

[27] AP I, art 85 (5).

[28] International Crimes and International Criminal Court Act 2000 (NZ).

[29] Crimes Against Humanity and War Crimes Act 2000 (CA).

[30] ICHL, rule 157.

[31] AP I, art 86; AP I, art 87; ICTY Statute, art 7(3); ICC Statute, art 28.

[32] Prosecutor v Tadić (Interlocutory Appeal Decision) ICTY-94–1-AR72 (2 October 1995) [134].

[33] Ibid [94].

 [34] United Nations Security Council (UNSC) Res 827 (25 May 1993) UN Doc S/RES/827.

[35] United Nations Security Council (UNSC) Res 955 (8 November 1994) UN Doc S/RES/955.

[36] ICC Statute, art 2 (8) (c)

[39] GC III, art 4 (2).

[41] Ibid.

[42] GC III, art 4 (A)(2).

[44] Melzer (n 39).

[45]Ibid 34.

[46] Ibid.

[47] Ibid.

[48] Ibid.

[49] Melzer 35.

[54] Melzer (n 54) 914.


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