Rule 6. Civilians’ Loss of Protection from Attack
Rule 6. Civilians are protected against attack, unless and for such time as they take a direct part in hostilities.
Summary
State practice establishes this rule as a norm of customary international law applicable in both international and non-international armed conflicts. The use of human shields is the subject of Rule 97.
International armed conflicts
The rule whereby civilians lose their protection against attack when and for such time as they take a direct part in hostilities is contained in Article 51(3) of Additional Protocol I, to which no reservations have been made.[1]  At the Diplomatic Conference leading to the adoption of the Additional Protocols, Mexico stated that Article 51 of Additional Protocol I was so essential that it “cannot be the subject of any reservations whatsoever since these would be inconsistent with the aim and purpose of Protocol I and undermine its basis”.[2]  Also at the Diplomatic Conference, the United Kingdom stated that the exception to the civilian immunity from attack contained in Article 51(3) was a “valuable reaffirmation” of an existing rule of customary international law.[3]  Upon ratification of the Convention on Certain Conventional Weapons, the United Kingdom declared that civilians enjoyed the protection of the Convention “unless and for such time as they take a direct part in hostilities”.[4] 
Numerous military manuals state that civilians are not protected against attack when they take a direct part in hostilities.[5]  The rule is supported by official statements and reported practice.[6]  This practice includes that of States not, or not at the time, party to Additional Protocol I.[7]  When the ICRC appealed to the parties to the conflict in the Middle East in October 1973, i.e., before the adoption of Additional Protocol I, to respect civilian immunity from attack, unless and for such time as they took a direct part in hostilities, the States concerned (Egypt, Iraq, Israel and Syria) replied favourably.[8] 
Non-international armed conflicts
Pursuant to Article 13(3) of Additional Protocol II, civilians are immune from direct attack “unless and for such time as they take a direct part in hostilities”.[9]  In addition, this rule is set forth in other instruments pertaining also to non-international armed conflicts.[10] 
The rule that civilians are not protected against attack when they take a direct part in hostilities is included in many military manuals which are applicable in or have been applied in non-international armed conflicts.[11] 
In the case concerning the events at La Tablada in Argentina, the Inter-American Commission on Human Rights held that civilians who directly take part in fighting, whether singly or as members of a group, thereby become legitimate military targets but only for such time as they actively participate in combat.[12] 
To the extent that members of armed opposition groups can be considered civilians (see commentary to Rule 5), this rule appears to create an imbalance between such groups and governmental armed forces. Application of this rule would imply that an attack on members of armed opposition groups is only lawful for "such time as they take a direct part in hostilities" while an attack on members of governmental armed forces would be lawful at any time. Such imbalance would not exist if members of armed opposition groups were, due to their membership, either considered to be continuously taking a direct part in hostilities or not considered to be civilians.
It is clear that the lawfulness of an attack on a civilian depends on what exactly constitutes direct participation in hostilities and, related thereto, when direct participation begins and when it ends. As explained below, the meaning of direct participation in hostilities has not yet been clarified. It should be noted, however, that whatever meaning is given to these terms, immunity from attack does not imply immunity from arrest and prosecution.
Definition
A precise definition of the term “direct participation in hostilities” does not exist. The Inter-American Commission on Human Rights has stated that the term “direct participation in hostilities” is generally understood to mean “acts which, by their nature or purpose, are intended to cause actual harm to enemy personnel and matériel”.[13]  Loss of protection against attack is clear and uncontested, as evidenced by several military manuals, when a civilian uses weapons or other means to commit acts of violence against human or material enemy forces.[14]  But there is also a lot of practice which gives little or no guidance on the interpretation of the term “direct participation”, stating, for example, that the assessment of direct participation has to be made on a case-by-case basis or simply repeating the general rule that direct participation causes civilians to lose protection against attack.[15]  The military manuals of Ecuador and the United States give several examples of acts constituting direct participation in hostilities, such as serving as guards, intelligence agents or lookouts on behalf of military forces.[16]  The Report on the Practice of the Philippines similarly considers that civilians acting as spies, couriers or lookouts lose their protection against attack.[17] 
In a report on human rights in Colombia, the Inter-American Commission on Human Rights sought to distinguish “direct” from “indirect” participation:
Civilians whose activities merely support the adverse party’s war or military effort or otherwise only indirectly participate in hostilities cannot on these grounds alone be considered combatants. This is because indirect participation, such as selling goods to one or more of the armed parties, expressing sympathy for the cause of one of the parties or, even more clearly, failing to act to prevent an incursion by one of the armed parties, does not involve acts of violence which pose an immediate threat of actual harm to the adverse party.[18] 
The distinction between direct and indirect participation had previously been developed by the Special Representative of the UN Commission on Human Rights for El Salvador.[19]  It is clear, however, that international law does not prohibit States from adopting legislation that makes it a punishable offence for anyone to participate in hostilities, whether directly or indirectly.
The Report on the Practice of Rwanda makes a distinction between acts that constitute direct participation in international and non-international armed conflicts and excludes logistical support in non-international armed conflicts from acts that constitute direct participation. According to the responses of Rwandan army officers to a questionnaire referred to in the report, unarmed civilians who follow their armed forces during an international armed conflict in order to provide them with food, transport munitions or carry messages, for example, lose their status as civilians. In the context of a non-international armed conflict, however, unarmed civilians who collaborate with one of the parties to the conflict always remain civilians. According to the report, this distinction is justified by the fact that in internal armed conflicts civilians are forced to cooperate with the party that holds them in its power.[20] 
It is fair to conclude, however, that outside the few uncontested examples cited above, in particular use of weapons or other means to commit acts of violence against human or material enemy forces, a clear and uniform definition of direct participation in hostilities has not been developed in State practice.[21] 
Several military manuals specify that civilians working in military objectives, for example, munitions factories, do not participate directly in hostilities but must assume the risks involved in an attack on that military objective.[22]  The injuries or death caused to such civilians are considered incidental to an attack upon a legitimate target which must be minimized by taking all feasible precautions in the choice of means and methods, for example, by attacking at night (see Rule 17). The theory that such persons must be considered quasi-combatants, liable to attack, finds no support in modern State practice.
Situations of doubt as to the character of a person
The issue of how to classify a person in case of doubt is complex and difficult. In the case of international armed conflicts, Additional Protocol I has sought to resolve this issue by stating that “in case of doubt whether a person is a civilian, that person shall be considered to be a civilian”.[23]  Some States have written this rule into their military manuals.[24]  Others have expressed reservations about the military ramifications of a strict interpretation of such a rule. In particular, upon ratification of Additional Protocol I, France and the United Kingdom expressed their understanding that this presumption does not override commanders’ duty to protect the safety of troops under their command or to preserve their military situation, in conformity with other provisions of Additional Protocol I.[25]  The US Naval Handbook states that:
Direct participation in hostilities must be judged on a case-by-case basis. Combatants in the field must make an honest determination as to whether a particular civilian is or is not subject to deliberate attack based on the person’s behavior, location and attire, and other information available at the time.[26] 
In the light of the foregoing, it is fair to conclude that when there is a situation of doubt, a careful assessment has to be made under the conditions and restraints governing a particular situation as to whether there are sufficient indications to warrant an attack. One cannot automatically attack anyone who might appear dubious.
In the case of non-international armed conflicts, the issue of doubt has hardly been addressed in State practice, even though a clear rule on this subject would be desirable as it would enhance the protection of the civilian population against attack. In this respect, the same balanced approach as described above with respect to international armed conflicts seems justified in non-international armed conflicts.

[1] Additional Protocol I, Article 51(3) (adopted by 77 votes in favour, one against and 16 abstentions) (cited in Vol. II, Ch. 1, § 755).
[2] Mexico, Statement at the Diplomatic Conference leading to the adoption of the Additional Protocols (ibid., § 800).
[3] United Kingdom, Statement at the Diplomatic Conference leading to the adoption of the Additional Protocols (ibid., § 803).
[4] United Kingdom, Declaration made upon ratification of the CCW (ibid., § 757).
[5] See, e.g., the military manuals of Australia (ibid., § 762), Benin (ibid., § 763), Canada (ibid., § 764), Colombia (ibid., § 765), Croatia (ibid., § 766), Dominican Republic (ibid., § 767), Ecuador (ibid., § 768), France (ibid., § 769), Germany (ibid., § 770), India (ibid., § 771), Indonesia (ibid., § 772), Italy (ibid., § 773), Kenya (ibid., § 774), Madagascar (ibid., § 775), Netherlands (ibid., §§ 776–777), New Zealand (ibid., § 778), Nigeria (ibid., §§ 779–780), South Africa (ibid., § 781), Spain (ibid., § 782), Sweden (ibid., § 783), Togo (ibid., § 784), United Kingdom (ibid., § 786), United States (ibid., §§ 787–788) and Yugoslavia (ibid., § 789).
[6] See, e.g., the statements of Belgium (ibid., § 792) and United States (ibid., §§ 804–806) and the reported practice of Chile (ibid., § 793), Jordan (ibid., § 796), Malaysia (ibid., § 799) and United States (ibid., § 807).
[7] See, e.g., the practice of France (ibid., § 769), India (ibid., § 771), Indonesia (ibid., § 772), Kenya (ibid., § 774), Malaysia (ibid., § 799), Nigeria (ibid., § 779), United Kingdom (ibid., § 786) and United States (ibid., §§ 787–788 and 804–807).
[8] See ICRC, The International Committee’s Action in the Middle East (ibid., § 813).
[9] Additional Protocol II, Article 13(3) (adopted by consensus) (ibid., § 756).
[10] See, e.g., Memorandum of Understanding on the Application of IHL between Croatia and the SFRY, para. 6 (ibid., § 759); Agreement on the Application of IHL between the Parties to the Conflict in Bosnia and Herzegovina, para. 2.5 (ibid., § 760); UN Secretary-General’s Bulletin, Section 5.2 (ibid., § 761).
[11] See, e.g., the military manuals of Australia (ibid., § 762), Benin (ibid., § 763), Colombia (ibid., § 765), Croatia (ibid., § 766), Ecuador (ibid., § 768), Germany (ibid., § 770), Italy (ibid., § 773), Kenya (ibid., § 774), Madagascar (ibid., § 775), Netherlands (ibid., § 776), Nigeria (ibid., § 779), South Africa (ibid., § 781), Spain (ibid., § 782), Togo (ibid., § 784) and Yugoslavia (ibid., § 789).
[12] Inter-American Commission on Human Rights, Case 11.137 (Argentina) (ibid., § 810).
[13] Inter-American Commission on Human Rights, Third report on human rights in Colombia (ibid., § 811).
[14] See., e.g., the military manuals of Australia (ibid., § 820), Belgium (ibid., § 821), Ecuador (ibid., § 822), El Salvador (ibid., § 823), India (ibid., § 824), Netherlands (ibid., § 825), United States (ibid., §§ 827 and 830) and Yugoslavia (ibid., § 831).
[15] See, e.g., Geneva Conventions, Common Article 3 (ibid., § 754); Additional Protocol I, Article 51(3) (adopted by 77 votes in favour, one against and 16 abstentions) (ibid., § 755); Additional Protocol II, Article 13(3) (adopted by consensus) (ibid., § 756); Memorandum of Understanding on the Application of IHL between Croatia and the SFRY, para. 6 (ibid., § 759); Agreement on the Application of IHL between the Parties to the Conflict in Bosnia and Herzegovina, para. 2.5 (ibid., § 760); UN Secretary-General’s Bulletin, Section 5.2 (ibid., § 761); the practice of Australia (ibid., § 762), Belgium (ibid., § 792), Benin (ibid., § 763), Canada (ibid., § 764), Colombia (ibid., § 765), Croatia (ibid., § 766), Dominican Republic (ibid., § 767), Ecuador (ibid., § 768), France (ibid., § 769), Germany (ibid., § 770), India (ibid., § 771), Indonesia (ibid., § 772), Italy (ibid., § 773), Jordan (ibid., § 796), Kenya (ibid., § 774), Madagascar (ibid., § 775), Malaysia (ibid., § 799), Netherlands (ibid., § 776), New Zealand (ibid., § 778), Spain (ibid., § 782), Sweden (ibid., § 783), Togo (ibid., § 784), United Kingdom (ibid., §§ 757 and 786), United States (ibid., §§ 787–788 and 804–806), Yugoslavia (ibid., § 789); Inter-American Commission on Human Rights, Case 11.137 (Argentina) (ibid., § 810).
[16] Ecuador, Naval Manual (ibid., § 822); United States, Naval Handbook (ibid., § 829).
[17] Report on the Practice of the Philippines (ibid., § 849).
[18] Inter-American Commission on Human Rights, Third report on human rights in Colombia (ibid., § 811).
[19] UN Commission on Human Rights, Special Representative on the Situation of Human Rights in El Salvador, Final Report (ibid., § 853).
[20] Report on the Practice of Rwanda (ibid., § 850).
[21] The ICRC has sought to clarify the notion of direct participation by means of a series of expert meetings that began in 2003.
[22] See, e.g., the military manuals of Australia (cited in Vol. II, Ch. 2, § 635), Canada (ibid., § 636), Colombia (ibid., § 637), Croatia (ibid., § 638), Ecuador (ibid., § 639), Germany (ibid., § 640), Hungary (ibid., § 641), Madagascar (ibid., § 642), Netherlands (ibid., § 643), New Zealand (ibid., § 644), Spain (ibid., §§ 645–646), Switzerland (ibid., § 647) and United States (ibid., § 648).
[23] Additional Protocol I, Article 50(1) (adopted by consensus) (cited in Vol. II, Ch. 1, § 887).
[24] See, e.g., the military manuals of Argentina (ibid., § 893), Australia (ibid., § 894), Cameroon (ibid., § 895), Canada (ibid., § 896), Colombia (ibid., § 897), Croatia (ibid., § 898), Hungary (ibid., § 900), Kenya (ibid., § 901), Madagascar (ibid., § 902), Netherlands (ibid., § 903), South Africa (ibid., § 904), Spain (ibid., § 905), Sweden (ibid., § 906) and Yugoslavia (ibid., § 908).
[25] France, Declarations and reservations made upon ratification of Additional Protocol I (ibid., § 888); United Kingdom, Declarations and reservations made upon ratification of Additional Protocol I (ibid., § 889).
[26] United States, Naval Handbook (ibid., § 830).