Rule 145. Reprisals
Rule 145. Where not prohibited by international law, belligerent reprisals are subject to stringent conditions.
Summary
State practice establishes this rule as a norm of customary international law applicable in international armed conflicts. A belligerent reprisal consists of an action that would otherwise be unlawful but that in exceptional cases is considered lawful under international law when used as an enforcement measure in reaction to unlawful acts of an adversary. In international humanitarian law there is a trend to outlaw belligerent reprisals altogether. Those that may still be lawful are subject to the stringent conditions set forth below.
International armed conflicts
As stated in several military manuals, reprisals have been a traditional method of enforcement of international humanitarian law, albeit subject to the stringent conditions mentioned below.[1]  During the past century the categories of persons and objects that can be subjected to reprisal action have been reduced, and reprisal action against certain persons and objects is now prohibited under customary international law (see Rules 146–147).
In the course of the many armed conflicts that have marked the past two decades, belligerent reprisals have not been resorted to as a measure of enforcing international humanitarian law, the main exception being the Iran–Iraq War, where such measures were severely criticized by the UN Security Council and UN Secretary-General (see infra). The trend towards outlawing reprisals, beyond those already prohibited by the Geneva Conventions, can be seen in a UN General Assembly resolution on basic principles for the protection of civilian populations in armed conflicts adopted in 1970, which stated that “civilian populations, or individual members thereof, should not be the object of reprisals”.[2] 
The reticence of States to resort to reprisals can be explained by the fact that they are ineffective as a means of enforcement, in particular because reprisals risk leading to an escalation of violations. As stated by Kenya’s LOAC Manual, “reprisals are an unsatisfactory way of enforcing the law. They tend to be used as an excuse for illegal methods of warfare and carry a danger of escalation through repeated reprisals and counter reprisals.”[3]  Several other military manuals, as well as other practice, similarly warn of the risk of escalation.[4]  Still others underline the limited military advantage gained by using reprisals.[5] 
During the negotiation of Additional Protocol I, a number of States asserted that resort to reprisals ought not to be allowed at all.[6]  Others stated that they were a very questionable means of securing enforcement.[7]  Several States prohibit reprisals altogether.[8]  Others state that they may only be taken against combatants and military objectives.[9]  There is also national case-law, as well as official statements, to the effect that reprisals must not be inhumane.[10]  This requirement was already set forth in the Oxford Manual and recently restated, albeit in different terms, in the Draft Articles on State Responsibility.[11] 
The reticence to approve of the resort to belligerent reprisals, together with the stringent conditions found in official practice, indicates that the international community is increasingly opposed to the use of violations of international humanitarian law as a method of trying to enforce the law. It is also relevant that there is much more support these days for the notion of ensuring respect for international humanitarian law through diplomatic channels than there was in the 19th and early 20th centuries, when the doctrine of belligerent reprisals as a method of enforcement was developed. In interpreting the condition that reprisal action may only be taken as a measure of last resort, when no other possibility is available, States must take into account the possibility of appealing to other States and international organizations to help put a stop to the violations (see also commentary to Rule 144).
Conditions
Five conditions must be met in order for belligerent reprisals against permitted categories of persons and objects not to be unlawful. Most of these conditions are laid down in military manuals and are supported by official statements. These conditions are:
(i) Purpose of reprisals. Reprisals may only be taken in reaction to a prior serious violation of international humanitarian law, and only for the purpose of inducing the adversary to comply with the law. This condition is set forth in numerous military manuals, as well as in the legislation of some States.[12]  It is also confirmed in national case-law.[13] 
Because reprisals are a reaction to a prior serious violation of international humanitarian law, “anticipatory” reprisals or “counter-reprisals” are not permissible, nor can belligerent reprisals be a reaction to a violation of another type of law. In addition, as reprisals are aimed at inducing the adversary to comply with the law, they may not be carried out for the purpose of revenge or punishment.
There is limited practice allowing reprisals against allies of the violating State but it dates back to the arbitration in the Cysne case in 1930 and to the Second World War.[14]  Practice since then appears to indicate that resort to such reprisals is no longer valid. According to the Draft Articles on State Responsibility, countermeasures are legitimate only “against a State which is responsible for an internationally wrongful act”.[15]  This element of responsibility is also reflected in some military manuals.[16]  However, whereas most military manuals remain silent on the question of reprisals against allies of the violating State, Italy’s IHL Manual expressly states that a reprisal can, “as a general rule, only be directed against the belligerent that violated the laws of war”.[17]  Other military manuals explain that reprisals are used against another State in order to induce that State to stop the violation of international law.[18] 
Some military manuals specify that in the light of their specific purpose, reprisals must be announced as such and publicized so that the adversary is aware of its obligation to comply with the law.[19] 
(ii) Measure of last resort. Reprisals may only be carried out as a measure of last resort, when no other lawful measures are available to induce the adversary to respect the law. This condition is set forth in many military manuals.[20]  It is confirmed by national case-law.[21]  It is also repeated in the statements and proposals made by States at the Diplomatic Conference leading to the adoption of the Additional Protocols, before the International Court of Justice in the Nuclear Weapons case and on other occasions, when it was sometimes mentioned that prior warning must be given and/or that other measures must have failed before resorting to reprisals.[22]  In its reservation concerning reprisals made upon ratification of Additional Protocol I, the United Kingdom reserved the right to take reprisal action “only after formal warning to the adverse party requiring cessation of the violations has been disregarded”.[23] 
According to the Draft Articles on State Responsibility, before taking countermeasures an injured State must call on the responsible State to fulfil its obligations, notify the responsible State of any decision to take countermeasures and offer to negotiate with that State.[24]  In its judgment in the Kupreškić case in 2000, the International Criminal Tribunal for the former Yugoslavia confirmed what had already been stated by the Special Arbitral Tribunal in the Naulilaa case in 1928, namely that reprisals may only be carried out after a warning to the adverse party requiring cessation of the violations has remained unheeded.[25] 
(iii) Proportionality. Reprisal action must be proportionate to the violation it aims to stop. This condition was already laid down in 1880 in the Oxford Manual and was recently reaffirmed in the Draft Articles on State Responsibility.[26]  It is also contained in many military manuals.[27]  Furthermore, there is case-law concerning violations committed in the Second World War in which the accused’s claims that their acts had been committed as lawful reprisals were rejected because, inter alia, they were found to be disproportionate to the original violation.[28] 
The requirement that reprisal measures be proportionate to the original wrong is repeated in various statements and proposals made by States at the Diplomatic Conference leading to the adoption of the Additional Protocols, before the International Court of Justice in the Nuclear Weapons case and on other occasions.[29]  In its reservation concerning reprisals made upon ratification of Additional Protocol I, the United Kingdom stated that “any measures thus taken by the United Kingdom will not be disproportionate to the violations giving rise thereto”.[30] 
The International Court of Justice in its advisory opinion in the Nuclear Weapons case in 1996 and the International Criminal Tribunal for the former Yugoslavia in its judgment in the Kupreškić case in 2000 confirmed what the Special Arbitral Tribunal had already stated in the Naulilaa case in 1928, namely that belligerent reprisals are subject to the principle of proportionality.[31] 
Most of the practice collected requires that acts taken in reprisal be proportionate to the original violation. Only a few pieces of practice specify that proportionality must be observed with regard to the damage suffered.[32] 
(iv) Decision at the highest level of government. The decision to resort to reprisals must be taken at the highest level of government. Whereas the Oxford Manual states that only a commander in chief is entitled to authorize reprisals,[33]  more recent practice indicates that such a decision must be taken at the highest political level.[34]  State practice confirming this condition is found in military manuals, as well as in some national legislation and official statements.[35]  In its reservation concerning reprisals made upon ratification of Additional Protocol I, the United Kingdom stated that reprisals would be taken “only after a decision taken at the highest level of government”.[36] 
In its judgment in the Kupreškić case in 2000, the International Criminal Tribunal for the former Yugoslavia held that the decision to resort to a reprisal must be taken at the highest political or military level and may not be decided by local commanders.[37] 
(v) Termination. Reprisal action must cease as soon as the adversary complies with the law. This condition, formulated as a formal prohibition in the event that the original wrong had been repaired, was already laid down in 1880 in the Oxford Manual and was recently restated in the Draft Articles on State Responsibility.[38]  It is also contained in several military manuals, official statements and reported practice.[39]  In its reservation concerning reprisals made upon ratification of Additional Protocol I, the United Kingdom stated that reprisals would not be continued “after the violations have ceased”.[40] 
In its judgment in the Kupreškić case in 2000, the International Criminal Tribunal for the former Yugoslavia confirmed that reprisal action must stop as soon as the unlawful act has been discontinued.[41] 

[1] See the military manuals of Benin (cited in Vol. II, Ch. 41, § 70), Kenya (ibid., § 82), Netherlands (ibid., § 85), Togo (ibid., § 93) and United Kingdom (ibid., §§ 94–95).
[2] See UN General Assembly, Res. 2675 (XXV) (adopted by 109 votes in favour, none against and 8 abstentions) (ibid., § 840).
[3] See Kenya, LOAC Manual (ibid., § 82).
[4] See, e.g., the military manuals of Australia (ibid., §§ 67–68), Sweden (ibid. , § 91), United Kingdom (ibid., §§ 94–95) and United States (ibid., §§ 97–99) and the practice of Argentina (ibid., § 115), Canada (ibid., § 119), Hungary (ibid., § 129), Mexico (ibid., § 134), Netherlands (ibid., § 136), Norway (ibid., § 137), Poland (ibid., § 139) and Bolivarian Republic of Venezuela (ibid., § 148).
[5] See, e.g., United States, Annotated Supplement to the Naval Handbook (ibid., § 100) (with respect to orders that no quarter will be given or that no prisoners will be taken); Canada, Ministry of Defence, Memorandum on Ratification of Additional Protocol I (ibid., § 120).
[6] See the practice of Belarus (ibid., § 118), Colombia (ibid., § 121), Czechoslovakia (ibid., § 122), Mexico (ibid., § 134), Poland (ibid., § 139) and USSR (ibid., § 142).
[7] See the practice of Canada (ibid., § 119), Federal Republic of Germany (ibid., § 126), Hungary (ibid., § 129), Netherlands (ibid., § 135) and Norway (ibid., § 137).
[8] See the military manuals of Burkina Faso (ibid., § 802), Cameroon (ibid., § 803), Congo (ibid., § 805) and Morocco (ibid., § 818).
[9] See the military manuals of Benin (ibid., § 801) and Togo (ibid., § 824).
[10] See, e.g., Italy, Military Tribunal of Rome, Kappler case (ibid., § 345), Priebke case (ibid., § 346) and Hass and Priebke case (ibid., § 347) and the official statements of Finland (ibid., § 348), India (ibid., § 349) and Malaysia (ibid., § 352).
[11] Oxford Manual, Article 86 (ibid., § 337); Draft Articles on State Responsibility, Article 50(1) (ibid., § 338).
[12] See, e.g., the military manuals of Australia (ibid., §§ 67–68), Belgium (ibid., § 69), Benin (ibid., § 70), Canada (ibid., § 71), Croatia (ibid., § 73), Ecuador (ibid., § 74), France (ibid., § 75), Germany (ibid., §§ 76–78), Hungary (ibid., § 79), Indonesia (ibid., § 80), Italy (ibid., § 81), Kenya (ibid., § 82), Netherlands (ibid., § 85), New Zealand (ibid., § 86), Nigeria (ibid., § 87), South Africa (ibid., § 89), Spain (ibid., § 90), Sweden (ibid., § 91), Switzerland (ibid., § 92), Togo (ibid., § 93), United Kingdom (ibid., §§ 94–95), United States (ibid., §§ 96–100) and Yugoslavia (ibid., § 101) and the legislation of Italy (ibid., § 103),
[13] See Italy, Military Tribunal of Rome, Priebke case (ibid., § 108); Italy, Military Tribunal of Rome (confirmed by the Military Appeals Court and the Supreme Court of Cassation), Hass and Priebke case (ibid., § 109); Netherlands, Special Court (War Criminals) at The Hague and Special Court of Cassation, Rauter case (ibid., § 110); Norway, Eidsivating Court of Appeal and Supreme Court, Bruns case (ibid., § 111); Norway, Frostating Court of Appeal and Supreme Court, Flesch case (ibid., § 112); United States, Military Tribunal at Nuremberg, List (Hostages Trial) case (ibid., § 113).
[14] See Special Arbitral Tribunal, Cysne case (ibid., § 156) and the reported practice of the United Kingdom during the Second World War (ibid., § 159).
[15] Draft Articles on State Responsibility, Article 49 (ibid., § 66).
[16] See the military manuals of Canada (ibid., § 71), Ecuador (ibid., § 74), New Zealand (ibid., § 86) and United States (ibid., §§ 97 and 99).
[17] Italy, IHL Manual (ibid., § 81).
[18] See, e.g., the military manuals of Germany (ibid., §§ 76 and 78); United States, Field Manual (reprisals are “resorted to by one belligerent against enemy personnel or property for acts of warfare committed by the other belligerent”) (ibid., § 96) and Air Force Pamphlet (“they are directed against an adversary in order to induce him to refrain from further violations of the law”) (ibid., § 97); see also the practice of Canada (“after that belligerent has violated the laws of war”) (ibid., § 120) and Netherlands (“to compel another State to cease a violation which that other State is committing”) (ibid., § 136).
[19] See the military manuals of Canada (ibid., § 71), Ecuador (ibid., § 74), New Zealand (ibid., § 86) and United States (ibid., §§ 97 and 99–100).
[20] See the military manuals of Australia (ibid., § 162), Belgium (ibid., § 163), Canada (ibid., § 165), Croatia (ibid., § 166), Ecuador (ibid., § 167), Germany (ibid., § 169), Hungary (ibid., § 170), Netherlands (ibid., § 173), Spain (ibid., § 176), United Kingdom (ibid., § 178), United States (ibid., §§ 180–183) and Yugoslavia (ibid., § 184). Other military manuals require that prior warning be given: see the military manuals of Benin (ibid., § 164), France (ibid., § 168), Hungary (ibid., § 170), Indonesia (ibid., § 171), Kenya (ibid., § 172), Togo (ibid., § 177) and United Kingdom (ibid., § 179).
[21] See Italy, Military Tribunal of Rome (confirmed by Military Appeals Court and Supreme Court of Cassation), Hass and Priebke case (ibid., § 186); Netherlands, Special Court (War Criminals), Rauter case (ibid., § 187); United States, Military Tribunal at Nuremberg, List (Hostages Trial) case (ibid., § 188).
[22] See, e.g., the practice of France (ibid., §§ 190–191), Netherlands (ibid., §§ 192–194), United Kingdom (ibid., § 195) and United States (ibid., §§ 196–197).
[23] United Kingdom, Reservation made upon ratification of Additional Protocol I (ibid., § 160).
[24] Draft Articles on State Responsibility, Article 52 (ibid., § 161).
[25] See ICTY, Kupreškić case, Judgment (ibid., § 202); Special Arbitral Tribunal, Naulilaa case (ibid., § 203).
[26] Oxford Manual, Article 86 (ibid., § 208); Draft Articles on State Responsibility, Article 51 (ibid., § 209).
[27] See the military manuals of Australia (ibid., § 210), Belgium (ibid., § 211), Benin (ibid., § 212), Canada (ibid., § 213), Croatia (ibid., § 214), Ecuador (ibid., § 215), Germany (ibid., § 216), Hungary (ibid., § 217), Italy (ibid., § 218), Kenya (ibid., § 219), Netherlands (ibid., § 220), New Zealand (ibid., § 221), Spain (ibid., § 223), Togo (ibid., § 224), United Kingdom (ibid., §§ 225–226), United States (ibid., §§ 227–230) and Yugoslavia (ibid., § 231).
[28] See Italy, Military Tribunal of Rome, Kappler case (ibid., § 233), Priebke case (ibid., § 234), (confirmed by Military Appeals Court and Supreme Court of Cassation) Hass and Priebke case (ibid., § 235); Netherlands, Special Court (War Criminals) and Special Court of Cassation, Rauter case (ibid., § 236); United States, Military Tribunal at Nuremberg, List (Hostages Trial) case (ibid., § 237).
[29] See, e.g., the statements of Canada (ibid., § 239), India (ibid., § 244), Mexico (ibid., § 245), Netherlands (ibid., §§ 246–247), United Kingdom (ibid., § 248) and United States (ibid., §§ 249–250) and the reported practice of China (ibid., § 240), France (ibid., §§ 241–242) and Germany (ibid., § 243).
[30] United Kingdom, Reservation made upon ratification of Additional Protocol I (ibid., § 207).
[31] ICJ, Nuclear Weapons case, Advisory Opinion (ibid., § 255); ICTY, Kupreškić case, Judgment (ibid., § 256); Special Arbitral Tribunal, Naulilaa case (ibid., § 257).
[32] See, e.g., the military manuals of Belgium (ibid., § 211), Netherlands (ibid., § 220) and Yugoslavia (ibid., § 231) and the statement of India (ibid., § 244).
[33] Oxford Manual, Article 86 (ibid., § 262).
[34] See the military manuals of Australia (ibid., § 264), Croatia (ibid., § 271), Ecuador (ibid., § 272), Germany (ibid., §§ 274–275), Hungary (ibid., § 276), Italy (ibid., § 277), Netherlands (ibid., § 280), New Zealand (ibid., § 281), Spain (ibid., § 283), Sweden (ibid., § 284), Switzerland (ibid., § 285), United Kingdom (for reprisals taken against the enemy civilian population or civilian objects) (ibid., § 288) and United States (ibid., §§ 290–294).
[35] See, e.g., the military manuals of Australia (ibid., § 263), Belgium (ibid., § 265), Benin (ibid., § 266), Canada (ibid., § 269), Kenya (ibid., § 278), South Africa (ibid., § 282), Togo (ibid., § 286), United Kingdom (ibid., § 287) and United States (ibid., § 289), the legislation of Argentina (ibid., § 296) and Italy (ibid., § 297) and the practice of France (ibid., §§ 299–300).
[36] United Kingdom, Reservation made upon ratification of Additional Protocol I (ibid., § 261).
[37] ICTY, Kupreškić case, Judgment (ibid., § 302).
[38] Oxford Manual, Article 85 (ibid., § 306); Draft Articles on State Responsibility, Article 53 (ibid., § 307).
[39] See, e.g., the military manuals of Benin (ibid., § 308), Canada (ibid., § 309), Croatia (ibid., § 310), Ecuador (ibid., § 311), Hungary (ibid., § 312), Italy (ibid., § 313), Kenya (ibid., § 314), New Zealand (ibid., § 315), Spain (ibid., § 317), Togo (ibid., § 318), United Kingdom (ibid., §§ 319–320), United States (ibid., §§ 321–322) and Yugoslavia (ibid., § 323) and the official statements of France (ibid., § 327) and Netherlands (ibid., § 328); the reported practice of the Islamic Republic of Iran (ibid., § 326).
[40] United Kingdom, Reservation made upon ratification of Additional Protocol I (ibid., § 305).
[41] ICTY, Kupreškić case, Judgment (ibid., § 333).