Practice Relating to Rule 145. Reprisals

No data.
Oxford Manual
Article 86 of the 1880 Oxford Manual provides: “In grave cases in which reprisals appear to be absolutely necessary, their nature and scope shall never exceed the measure of the infraction of the laws of war committed by the enemy.” 
The Laws of War on Land, adopted by the Institute of International Law, Oxford, 9 September 1880, Article 86.
ILC Draft Articles on State Responsibility
Article 51 of the 2001 ILC Draft Articles on State Responsibility, entitled “Proportionality”, provides: “Countermeasures must be commensurate with the injury suffered, taking into account the gravity of the internationally wrongful act and the rights in question.” 
Draft Articles on Responsibility of States for Internationally Wrongful Acts, adopted by the International Law Commission, reprinted in Report of the International Law Commission on the work of its fifty-third session, 23 April–1 June and 2 July–10 August 2001, UN Doc. A/56/10, 2001, Article 51.
Australia
Australia’s Defence Force Manual (1994) and Commanders’ Guide (1994) state: “In any case, reprisals must be timely, responsive to the enemy’s conduct [and] proportional.” 
Australia, Manual on Law of Armed Conflict, Australian Defence Force Publication, Operations Series, ADFP 37 – Interim Edition, 1994, § 1310; Law of Armed Conflict, Commanders’ Guide, Australian Defence Force Publication, Operations Series, ADFP 37 Supplement 1 – Interim Edition, 7 March 1994, § 1211.
Australia
Australia’s LOAC Manual (2006) states:
In order to qualify as a legitimate reprisal, an act must comply with the following conditions when employed … [including] … A reprisal must be in proportion to the original violation. Whilst a reprisal need not conform in kind to the act complained of, it may not significantly exceed the adverse party’s violation either in degree or effect. Effective but disproportionate acts cannot be justified as reprisals on the basis that only an excessive response will forestall further violations. 
Australia, The Manual of the Law of Armed Conflict, Australian Defence Doctrine Publication 06.4, Australian Defence Headquarters, 11 May 2006, § 13.18.
The LOAC Manual (2006) replaces both the Defence Force Manual (1994) and the Commanders’ Guide (1994).
Belgium
Belgium’s Law of War Manual (1983) states that, when recourse is made to reprisals, the following conditions must be fulfilled: “3) the damage suffered by the adversary must be proportionate to the damage that he has caused”. 
Belgium, Droit Pénal et Disciplinaire Militaire et Droit de la Guerre, Deuxième Partie, Droit de la Guerre, Ecole Royale Militaire, par J. Maes, Chargé de cours, Avocat-général près la Cour Militaire, D/1983/1187/029, 1983, p. 35.
Benin
Benin’s Military Manual (1995) states that reprisals “may only be used if: … they are proportional to the violation of the law of war committed by the enemy”. 
Benin, Le Droit de la Guerre, III fascicules, Forces Armées du Bénin, Ministère de la Défense nationale, 1995, Fascicule III, p. 13.
Canada
Canada’s LOAC Manual (1999) states:
[The reprisal] must be proportionate to the original wrongdoing, and must be terminated as soon as the original wrongdoer ceases the illegal actions. Proportionality is not strict, for, if the reprisal is to be effective, it may often be greater than the original wrongdoing. Nevertheless, there must be a reasonable relationship between the original wrong and the reprisal measure. 
Canada, The Law of Armed Conflict at the Operational and Tactical Level, Office of the Judge Advocate General, 1999, p. 15-2, § 14.
The manual further provides:
To qualify as a reprisal, an act must satisfy the following conditions:
f. A reprisal must be proportional to the original violation. Although a reprisal need not conform in kind to the same type of acts complained of (bombardment for bombardment, weapon for weapon) it may not significantly exceed the adversary’s violation either in violence or effect. 
Canada, The Law of Armed Conflict at the Operational and Tactical Level, Office of the Judge Advocate General, 1999, p. 15-3, § 17.
Canada
Canada’s LOAC Manual (2001) states in its chapter entitled “Preventative and enforcement measures and the role of protecting powers”:
3. Reprisal is not a retaliatory act or a simple act of vengeance. It must be proportionate to the original wrongdoing, and must be terminated as soon as the original wrongdoer ceases the illegal actions. Proportionality is not strict, for, if the reprisal is to be effective, it may often be greater than the original wrongdoing. Nevertheless, there must be a reasonable relationship between the original wrong and the reprisal measure.
6. To qualify as a reprisal, an act must satisfy the following conditions:
f. A reprisal must be proportional to the original violation. Although a reprisal need not conform in kind to the same type of acts complained of (bombardment for bombardment, weapon for weapon) it may not significantly exceed the adversary’s violation either in violence or effect. 
Canada, The Law of Armed Conflict at the Operational and Tactical Levels, Office of the Judge Advocate General, 13 August 2001, § 1507.3 and 6.f.
Central African Republic
The Central African Republic’s Instructor’s Manual (1999) states in Volume 3 (Instruction for non-commissioned officers studying for the level 1 and 2 certificates and for future officers of the criminal police): “Reprisals are permitted under customary law if they are made in response to an unlawful act of war. Reprisals may be made only if: … they are proportional to the violation of the law of war committed by the enemy”. 
Central African Republic, Le Droit de la Guerre, Fascicule No. 3: Formation pour l’obtention du Brevet d’Armes No. 1, du Brevet d’Armes No. 2 et le stage d’Officier de Police Judiciaire (OPJ), Ministère de la Défense, Forces Armées Centrafricaines, 1999, Chapter I, Section I.
Chad
Chad’s Instructor’s Manual (2006) states that any reprisal action “must be in keeping with the breach of the law committed by the enemy”. 
Chad, Droit international humanitaire, Manuel de l’instructeur en vigueur dans les forces armées et de sécurité, Ministère de la Défense, Présidence de la République, Etat-major des Armées, 2006, p. 93.
Croatia
Croatia’s LOAC Compendium (1991) states that a condition for reprisals is that they be “proportionate”. 
Croatia, Compendium “Law of Armed Conflicts”, Republic of Croatia, Ministry of Defence, 1991, p. 19.
Ecuador
Ecuador’s Naval Manual (1989) provides: “To be valid, a reprisal action must conform to the following criteria: … 6. Each reprisal must be proportional to the original violation.” 
Ecuador, Aspectos Importantes del Derecho Internacional Marítimo que Deben Tener Presente los Comandantes de los Buques, Academia de Guerra Naval, 1989, § 6.2.3.1.
Germany
Germany’s Military Manual (1992) provides: “Reprisals shall not be excessive in relation to the offence committed by the adversary.” 
Germany, Humanitarian Law in Armed Conflicts – Manual, DSK VV207320067, edited by The Federal Ministry of Defence of the Federal Republic of Germany, VR II 3, August 1992, English translation of ZDv 15/2, Humanitäres Völkerrecht in bewaffneten KonfliktenHandbuch, August 1992, § 478.
Hungary
Hungary’s Military Manual (1992) states that a condition for reprisals is that they be “proportionate”. 
Hungary, A Hadijog, Jegyzet a Katonai, Föiskolák Hallgatói Részére, Magyar Honvédség Szolnoki Repülötiszti Föiskola, 1992, p. 35.
Italy
Italy’s IHL Manual (1991) provides: “The reprisal must be sufficiently proportionate to the gravity of the offence suffered and may not consist, except in cases of absolute necessity, in belligerent acts directed against the civilian population.” 
Italy, Manuale di diritto umanitario, Introduzione e Volume I, Usi e convenzioni di Guerra, SMD-G-014, Stato Maggiore della Difesa, I Reparto, Ufficio Addestramento e Regolamenti, Rome, 1991, Vol. I, § 23.
Kenya
Kenya’s LOAC Manual (1997) states: “Under customary law, reprisals are permitted to counter unlawful acts of warfare. They can only be taken if: … they are proportionate to the breach of the law of war committed by the enemy.” 
Kenya, Law of Armed Conflict, Military Basic Course (ORS), 4 Précis, The School of Military Police, 1997, Précis No. 4, p. 4.
Netherlands
The Military Manual (1993) of the Netherlands, referring to customary law, states that reprisals are in principle allowed, provided that a number of conditions are fulfilled. Among these conditions, it states: “The damage to be caused to the adversary and the damage unlawfully suffered must be proportional.” 
Netherlands, Toepassing Humanitair Oorlogsrecht, Voorschift No. 27-412/1, Koninklijke Landmacht, Ministerie van Defensie, 1993, p. IV-5.
Netherlands
The Military Manual (2005) of the Netherlands states:
On the basis of customary law, it used to be assumed that reprisals were allowed in principle by the law of war, provided that a number of conditions were met:
- there must be proportionality between the damage to be done and the damage found to be unjust. 
Netherlands, Humanitair Oorlogsrecht: Handleiding, Voorschift No. 27-412, Koninklijke Landmacht, Militair Juridische Dienst, 2005, § 0423.
New Zealand
New Zealand’s Military Manual (1992) states:
[The reprisal] must be proportionate to the original wrongdoing … The proportionality is not strict: if the reprisal is to be effective, it will often be greater than the original wrongdoing. Nevertheless, there must be a reasonable relationship between the original wrong and the reprisal measure. 
New Zealand, Interim Law of Armed Conflict Manual, DM 112, New Zealand Defence Force, Headquarters, Directorate of Legal Services, Wellington, November 1992, § 1606(1).
The manual further states:
In order to be considered a reprisal, an act must have certain characteristics: … A reprisal must be proportional to the original violation. Although a reprisal need not conform in kind to the same type of acts complained of (bombardment for bombardment, weapon for weapon) it may not significantly exceed the adverse Party’s violation either in violence or in effect. Effective but disproportionate reprisals cannot be justified by the argument that only an excessive response will forestall further transgressions. 
New Zealand, Interim Law of Armed Conflict Manual, DM 112, New Zealand Defence Force, Headquarters, Directorate of Legal Services, Wellington, November 1992, § 1606(4)(f).
Peru
Peru’s IHL Manual (2004) states with regard to reprisals: “The action taken must be proportional to the violation”. 
Peru, Manual de Derecho Internacional Humanitario para las Fuerzas Armadas, Resolución Ministerial Nº 1394-2004-DE/CCFFAA/CDIH-FFAA, Lima, 1 December 2004, § 25.c.(5).
Peru
Peru’s IHL and Human Rights Manual (2010) states: “The action taken must be proportional to the violation”. 
Peru, Manual de Derecho Internacional Humanitario y Derechos Humanos para las Fuerzas Armadas, Resolución Ministerial No. 049-2010/DE/VPD, Lima, 21 May 2010, § 29(c)(5), p. 234.
South Africa
South Africa’s LOAC Manual (1996) states that “reprisals are only permitted according to strict criteria”. 
South Africa, Presentation on the South African Approach to International Humanitarian Law, Appendix A, Chapter 4: International Humanitarian Law (The Law of Armed Conflict), National Defence Force, 1996, § 34(e).
South Africa
South Africa’s LOAC Teaching Manual (2008) states:
Reprisals
- Under customary international law, reprisals against persons and objects not protected against reprisals can be justified if the reprisals meet certain criteria, including the following:
- Reprisals must be proportionate to the illegal acts complained of and not excessive to the goal of ensuring enemy compliance with the law. 
South Africa, Advanced Law of Armed Conflict Teaching Manual, School of Military Justice, 1 April 2008, as amended to 25 October 2013, Learning Unit 3, pp. 194–195.
Spain
Spain’s LOAC Manual (1996) states: “The action must be in proportion to the violation committed by the enemy.” 
Spain, Orientaciones. El Derecho de los Conflictos Armados, Publicación OR7-004, 2 Tomos, aprobado por el Estado Mayor del Ejército, Division de Operaciones, 18 March 1996, Vol. I, § 3.3.c.(5)(a).
Togo
Togo’s Military Manual (1996) states that reprisals “may only be used if: … they are proportional to the violation of the law of war committed by the enemy”. 
Togo, Le Droit de la Guerre, III fascicules, Etat-major Général des Forces Armées Togolaises, Ministère de la Défense nationale, 1996, Fascicule III, p. 13.
Ukraine
Ukraine’s IHL Manual (2004) states: “Reprisals … shall be proportionate to violations by the enemy”. 
Ukraine, Manual on the Application of IHL Rules, Ministry of Defence, 11 September 2004, § 1.2.18.
United Kingdom of Great Britain and Northern Ireland
The UK Military Manual (1958) states:
What kinds of acts should be resorted to as reprisals is a matter for consideration by the injured party. Acts done by way of reprisals must not, however, be excessive. They must bear a reasonable relation to the degree of violation committed by the enemy. 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, § 648.
In a footnote relating to this provision, the manual refers to the Nuremberg trials and states:
Acts of reprisal that are grossly excessive against non-protected persons … constitute a war crime. During the Second World War German forces applied a “hundred to one” order in occupied territories, whereby one hundred civilians would be seized at random and shot as a reprisal for the killing of one German. On occasions civilians already held as prisoners were shot in the same proportion. 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, § 648, footnote 1.
United Kingdom of Great Britain and Northern Ireland
The UK LOAC Pamphlet (1981) states that reprisals can only be taken if “they are in proportion to the violation complained of”. 
United Kingdom, The Law of Armed Conflict, D/DAT/13/35/66, Army Code 71130 (Revised 1981), Ministry of Defence, prepared under the Direction of The Chief of the General Staff, 1981, Section 4, p. 17, § 14(c).
United Kingdom of Great Britain and Northern Ireland
The UK LOAC Manual (2004) states:
A reprisal must be in proportion to the original violation. Whilst a reprisal need not conform in kind to the act complained of, it may not significantly exceed the adverse party’s violation either in degree or effect. Effective but disproportionate acts cannot be justified as reprisals on the basis that only an excessive response will forestall further violations. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 16.17.
The manual also restates the interpretative declaration made by the UK upon ratification of the 1977 Additional Protocol I (see infra). 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 16.19.1.
United States of America
The US Field Manual (1956) states:
Form of Reprisal. What kinds of acts should be resorted to as reprisals is a matter for consideration by the injured party. Acts done by way of reprisals must not, however, be excessive. They must bear reasonable relation to the degree of violation committed by the enemy. 
United States, Field Manual 27-10, The Law of Land Warfare, US Department of the Army, 18 July 1956, as modified by Change No. 1, 15 July 1976, § 497(e).
United States of America
The US Air Force Pamphlet (1976) states:
A reprisal must be proportional to the original violation. Although a reprisal need not conform in kind to the same type of acts complained of (bombardment for bombardment, weapon for weapon) it may not significantly exceed the adversary’s violation either in violence or effect. Effective but disproportionate reprisals cannot be justified by the argument that only an excessive response will forestall further transgressions. 
United States, Air Force Pamphlet 110-31, International Law – The Conduct of Armed Conflict and Air Operations, US Department of the Air Force, 1976, § 10-7(c)(6).
United States of America
The US Naval Handbook (1995) provides: “To be valid, a reprisal action must conform to the following criteria: … 6. Each reprisal must be proportional to the original violation.” 
United States, The Commander’s Handbook on the Law of Naval Operations, NWP 1-14M/MCWP 5-2.1/COMDTPUB P5800.7, issued by the Department of the Navy, Office of the Chief of Naval Operations and Headquarters, US Marine Corps, and Department of Transportation, US Coast Guard, October 1995 (formerly NWP 9 (Rev. A)/FMFM 1-10, October 1989), § 6.2.3.1.
United States of America
The Annotated Supplement to the US Naval Handbook (1997) states:
This rule [that a reprisal must be proportional to the original violation] is not of strict equivalence because the reprisal will usually be somewhat greater that the initial violation that gave rise to it. However, care must be taken that the extent of the reprisal is measured by some degree of proportionality and not solely by effectiveness. Effective but disproportionate reprisals cannot be justified by the argument that only an excessive response will forestall a further transgression … The acts resorted to by way of reprisal need not conform in kind to those complained of by the injured belligerent. The reprisal action taken may be quite different from the original act which justified it, but should not be excessive or exceed the degree of harm required to deter the enemy from continuance of his initial unlawful conduct. 
United States, Annotated Supplement to the Commander’s Handbook on the Law of Naval Operations, prepared by the Oceans Law and Policy Department, Center for Naval Warfare Studies, Naval War College, Newport, Rhode Island, November 1997, § 6.2.3.1, footnote 43.
United States of America
The US Naval Handbook (2007) states: “To be valid, a reprisal action must conform to the following criteria: … 6. Each reprisal must be proportional to the original violation.” 
United States, The Commander’s Handbook on the Law of Naval Operations, NWP 1-14M/MCWP 5-12.1/COMDTPUB P5800.7, issued by the Department of the Navy, Office of the Chief of Naval Operations and Headquarters, US Marine Corps, and Department of Homeland Security, US Coast Guard, July 2007, § 6.2.4.1.
Yugoslavia, Socialist Federal Republic of
The Socialist Federal Republic of Yugoslavia’s Military Manual (1988) states: “Reprisals may be undertaken by application of the same or similar measures. The consequences of such measures must be proportionate to the consequences that the enemy caused by violating the laws of war.” 
Yugoslavia, Socialist Federal Republic of, Propisi o Primeri Pravila Medjunarodnog Ratnog Prava u Oruzanim Snagama SFRJ, PrU-2, Savezni Sekretarijat za Narodnu Odbranu (Pravna Uprava), 1988, § 27.
The manual further states:
When reprisals are undertaken, care must be taken that they be in proportion to the seriousness of the violations committed by the enemy, that is, that the seriousness of the reprisals undertaken corresponds to the seriousness of the violations of the laws of war committed by the enemy. 
Yugoslavia, Socialist Federal Republic of, Propisi o Primeri Pravila Medjunarodnog Ratnog Prava u Oruzanim Snagama SFRJ, PrU-2, Savezni Sekretarijat za Narodnu Odbranu (Pravna Uprava), 1988, § 29.
No data.
Italy
In its judgment in the Kappler case in 1948, Italy’s Military Tribunal of Rome found that the massacre of 335 prisoners in the Ardeatine Caves, ordered as a reprisal for a bomb attack by the Italian resistance which killed 33 German military policemen, was disproportionate, because of the ratio of 10:1 and because of the ranks of the executed Italian prisoners. 
Italy, Military Tribunal of Rome, Kappler case, Judgment, 20 July 1948.
Italy
In its judgment in the Priebke case in 1996 in connection with the Ardeatine Caves massacre during the Second World War, Italy’s Military Tribunal of Rome stated: “The principle of proportionality has never been questioned by international law scholars, as it finds its origin in the unquestionable axioms of rationality.” The Tribunal found that the executions were grossly disproportionate. 
Italy, Military Tribunal of Rome, Priebke case, Judgment in Trial of First Instance, 1 August 1996, Section 7.
Italy
In its judgment in the Hass and Priebke case in 1997 concerning the Ardeatine Caves massacre during the Second World War, Italy’s Military Tribunal of Rome, with respect to the conditions required for a reprisal, stated: “Also such a reaction must be proportionate to the damage suffered.” It found unacceptable the disproportion between the deaths of 33 German soldiers and the execution of 335 persons. 
Italy, Military Tribunal of Rome, Hass and Priebke case, Judgment in Trial of First Instance, 22 July 1997, Section 4.
In its relevant parts, the decision was confirmed by the Military Appeals Court and the Supreme Court of Cassation. 
Italy, Military Appeals Court, Hass and Priebke case, Judgment on Appeal, 7 March 1998; Supreme Court of Cassation, Hass and Priebke case, Judgment in Trial of Third Instance, 16 November 1998.
Netherlands
In its judgment in the Rauter case in 1948, the Special Court (War Criminals) at The Hague referred to the judgment of the US Military Tribunal at Nuremberg in the List case (The Hostages Trial), as well as to the conditions required for reprisals in general by the UK and US military regulations and stated that, accordingly, the taking of reprisals required a due proportion between the acts undertaken in reprisals and the original offence. It found, inter alia, that by killing several hostages at a time for the death of one member of the German authorities, the accused had committed excessive reprisals in violation of the rule requiring due proportion. 
Netherlands, Special Court (War Criminals) at The Hague, Rauter case, Judgment, 4 May 1948.
In its judgment on appeal in 1949, the Special Court of Cassation of the Netherlands also stated, inter alia, that genuine reprisals may be taken, “provided they are taken within certain limits and provided attention is paid to a certain proportion”. 
Netherlands, Special Court of Cassation, Rauter case, Judgment, 12 January 1949.
United States of America
In its judgment in the List case (The Hostages Trial) in the late 1940s, the US Military Tribunal at Nuremberg stated: “It is a fundamental rule that a reprisal may not exceed the degree of the criminal act it is designed to correct. Where an excess is knowingly indulged, it in turn is criminal and may be punished.” 
United States, Military Tribunal at Nuremberg, List case (The Hostages Trial), Judgment, 8 July 1947–19 February 1948.
Belgium
In 1967, a Belgian Senator stated with respect to bombardments of North Vietnam by the United States: “It is recognized today that [reprisals] must be proportionate to the injury suffered. In case one has not suffered any damage, as it was the case, it is incomprehensible to pretend to start a period of bombardments on North Vietnam, as reprisals for attacks on the high sea.” 
Belgium, Parliamentary Debates, 30 November 1967, Annales Parlementaires, Senate, p. 95, reprinted in RBDI, Vol. 6, 1970, pp. 656–657.
Canada
In 1986, in an annex to a memorandum on Canada’s attitude to possible reservations with regard to the 1977 Additional Protocol I, the Canadian Ministry of Defence noted: “The act of reprisal must be proportional to the illegal act or acts committed by the other belligerent.” 
Canada, Ministry of Defence, Memorandum on Ratification of the 1977 Additional Protocol I, Reprisals Reservation, Operational Considerations, Doc. 3440-13-2 (D Law/I), 14 March 1986, Annex A, § 1.
China
According to the Report on the Practice of China, in 1972, during the conflict in the Middle East, China condemned Israeli reprisals allegedly “not in conformity with the principle of proportionality”. 
Report on the Practice of China, 1997, Chapter 2.9, referring to a Statement on the Middle East made by the Vice Foreign Minister, 5 December 1972.
France
At the CDDH, France made a proposal for a draft article on reprisals within the 1977 Additional Protocol I – which it later withdrew – which read, inter alia, as follows:
2.… The prohibition [of the taking of reprisals] may be waived on condition:
(d) that the means of application and the extent of such measures, if it proves imperative to take them, shall in no case exceed the extent of the breach which they are designed to end. 
France, Draft Article 74 bis Additional Protocol I submitted to the CDDH, Official Records, Vol. III, CDDH/I/ 221, 19 February 1975, p. 323.
France
At the CDDH, France made another proposal for a draft article on reprisals within the 1977 Additional Protocol I – which it later withdrew – which read, inter alia, as follows:
3. If it proves imperative to take these measures, their extent and their means of application shall in no case exceed the extent of the breach which they are designed to end. The measures may not involve any actions prohibited by the Geneva Conventions of 1949. 
France, Draft Article 74 bis Additional Protocol I submitted to the CDDH, Official Records, Vol. III, CDDH/I/ 221/Rev.1, 22 April 1976, p. 324.
Germany, Federal Republic of
At the CDDH, the Federal Republic of Germany, with regard to the French proposal for a draft article on reprisals, held that the principle of proportionality laid down therein was based on “precedents established in 1928 and 1930, which were now universally recognised”. 
Germany, Federal Republic of, Statement at the CDDH, Official Records, Vol. IX, CDDH/I/SR.48, 30 April 1976, p. 84, § 6.
India
In its written statement submitted to the ICJ in the Nuclear Weapons case in 1995, India stated:
Reprisals or retaliation under international law are also governed by certain specific principles … Reprisals must remain within reasonable bounds of proportionality to the effect created by the original wrongful act … In other words … when a State commits … a wrongful act or delict, the use of force by way of reprisal would have to be proportionate and as such if the wrongful act did not involve the use of a nuclear weapon, the reprisal could also not involve the use of a nuclear weapon … In view of the above, use of nuclear weapons, even by way of reprisal or retaliation, appears to be unlawful. In any case, if the wrongful use of force in the first instance did not involve the use of nuclear weapons, it is beyond doubt that even in response by way of retaliation States do not have the right to use nuclear weapons because of their special quality as weapons of mass destruction. 
India, Written statement submitted to the ICJ, Nuclear Weapons case, 20 June 1995, p. 2.
Mexico
In its oral pleadings before the ICJ in the Nuclear Weapons case in 1995, Mexico stated: “In the opinion of my country the use of nuclear weapons in reprisal – or any other pretext – against a non-nuclear attack is contrary to the principle of proportionality.” 
Mexico, Oral pleadings before the ICJ, Nuclear Weapons case, CR 95/25, 3 November 1995, p. 51.
Netherlands
In an explanatory memorandum submitted to the Dutch Parliament in the context of the ratification procedure of the Additional Protocols, the Government of the Netherlands stated that for the reprisal to be lawful, “the violation of the law caused by the reprisal must be proportionate with the violation(s) committed by the adverse party”. 
Netherlands, Lower House of Parliament, Explanatory memorandum for the ratification of the Additional Protocols, 1983–1984 Session, Doc. 18 277 (R 1247), No. 3, pp. 40.
Netherlands
In its written statement submitted to the ICJ in the Nuclear Weapons case in 1995, the Netherlands stated:
The Netherlands Government … believes that even if it were to be assumed that the (first) use of nuclear weapons by a State were unlawful per se under present international law – quod non -, this would not necessarily exclude the permissibility of the use of nuclear weapons by way of belligerent reprisal against an unlawful use of (nuclear) weapons, provided of course the retaliating State observed the conditions set by international law for the taking of lawful reprisals, i.e. satisfies, inter alia, the requirement that the retaliation is proportionate and serves as an ultimum remedium. 
Netherlands, Written statement submitted to the ICJ, Nuclear Weapons case, 16 June 1995, § 29.
[emphasis in original]
United Kingdom of Great Britain and Northern Ireland
In its written statement submitted to the ICJ in the Nuclear Weapons case in 1995, the United Kingdom stated:
To be lawful, a belligerent reprisal must meet two conditions … It must meet the criteria for the regulation of reprisals, namely that it is … proportionate … It has been argued that the use of nuclear weapons could never satisfy the requirements of proportionality … This argument, however, suffers from the same flaws as the argument that the use of nuclear weapons could never satisfy the requirements of self-defence. Whether the use of nuclear weapons would meet the requirements of proportionality cannot be answered in the abstract: it would depend upon the nature and circumstances of the wrong which prompted the taking of reprisal action. 
United Kingdom, Written statement submitted to the ICJ, Nuclear Weapons case, 16 June 1995, pp. 58–60.
United Kingdom of Great Britain and Northern Ireland
Upon ratification of the 1977 Additional Protocol I, the United Kingdom stated that in the event of violations of Articles 51–55 of the 1977 Additional Protocol I by the adversary, the United Kingdom would regard itself entitled to take measures otherwise prohibited by these Articles, noting, however, that “any measures thus taken by the United Kingdom will not be disproportionate to the violations giving rise thereto”. 
United Kingdom, Reservations and declarations made upon ratification of the 1977 Additional Protocol I, 28 January 1998, § (m).
United States of America
In 1980, in a footnote to a memorandum of law on the “Reported Use of Chemical Agents in Afghanistan, Laos, and Kampuchea”, a legal adviser of the US Department of State noted: “Reprisals are permitted under the laws of war … only in proportion to the original violations.” 
United States, Department of State, Memorandum of law by a Legal Adviser on the “Reported Use of Chemical Agents in Afghanistan, Laos, and Kampuchea”, 9 April 1980, reprinted in Marian Nash Leich, Digest of United States Practice in International Law, 1980, Department of State Publication 9610, Washington, D.C., December 1986, pp. 1034 and 1041, footnote 38.
United States of America
In its written statement submitted to the ICJ in the Nuclear Weapons case in 1995, the United States stated:
Reprisals would be lawful if conducted in accordance with the applicable principles governing belligerent reprisals. Specifically … the reprisals must be proportionate to the violations [of the law of armed conflict by the enemy] … As in the case of other requirements of the law of armed conflict, a judgment about compliance of any use of nuclear weapons with these requirements would have to be made on the basis of the actual circumstances in each case, and could not be made in advance or in the abstract. 
United States, Written statement submitted to the ICJ, Nuclear Weapons case, 20 June 1995, p. 30.
UN General Assembly
In 2001, the UN General Assembly adopted a resolution on responsibility of States for internationally wrongful acts, to which the 2001 ILC Draft Articles on State Responsibility, and thus Article 51 entitled “Proportionality”, were annexed. In the resolution, the General Assembly took note of the Draft Articles and commended them to the attention of governments “without prejudice to the question of their future adoption or other appropriate action”. 
UN General Assembly, Res. 56/83, 12 December 2001, § 3 and Annex, adopted without a vote.
UN Commission of Experts Established pursuant to Security Council Resolution 780 (1992)
In 1994, in its final report on grave breaches of the Geneva Conventions and other violations of IHL committed in the former Yugoslavia, the UN Commission of Experts Established pursuant to Security Council Resolution 780 (1992) stated that a reprisal “must be proportionate to the original wrongdoing”. It added: “The proportionality is not strict, for if the reprisal is to be effective, it will often be greater than the original wrongdoing. Nevertheless, there must be a reasonable relationship between the original wrong and the reprisal measure.” 
UN Commission of Experts Established pursuant to Security Council Resolution 780 (1992), Final report, UN Doc. S/1994/674, 27 May 1994, § 64.
No data.
No data.
International Court of Justice
In its advisory opinion in the Nuclear Weapons case in 1996, the ICJ observed: “In any case any right of recourse to such reprisals would, like self-defence, be governed inter alia by the principle of proportionality.” 
ICJ, Nuclear Weapons case, Advisory Opinion, 8 July 1996, § 46.
International Criminal Tribunal for the former Yugoslavia
In its judgment in the Kupreškić case in 2000, the ICTY Trial Chamber stated:
It should also be pointed out that at any rate, even when considered lawful, reprisals are restricted by … the principle of proportionality (which entails not only that the reprisals must not be excessive compared to the precedent unlawful act of warfare, but also that they must stop as soon as that unlawful act has been discontinued). 
ICTY, Kupreškić case, Judgment, 14 January 2000, § 535.
Special Arbitral Tribunal
In its judgment in the Naulilaa case in 1928 regarding acts taken by Germany against Portugal in reprisal for the killing of three German officials by Portuguese soldiers, the Special Arbitral Tribunal stated:
The definition of reprisals does not require that the reprisal be proportionate to the offence. On this issue, the writers, unanimous until recently, start being divided in their opinions. In a certain proportionality between offence and reprisal the majority sees a necessary condition for the legitimacy of [reprisals]. Other writers, among the most modern ones, do not require this condition any more. As regards international law … it certainly tends to limit the notion of legitimate reprisals and prohibit excess.
The Tribunal went on to say:
Even if one should assume that the law of nations does not require that the reprisal is approximatively measured with relation to the offence, one must certainly consider as being excessive and … illicit reprisals out of any proportion to the act which has caused them and that, even if it had been admitted that the conduct of the Portuguese authorities had been internationally wrongful, the German reprisals would still have been wrongful, for, inter alia, they were disproportionate to the alleged wrong. 
Special Arbitral Tribunal, Naulilaa case, Decision, 31 July 1928, pp. 1026 and 1028.
No data.
American Law Institute
The Restatement (Third) of the Foreign Relations Law of the United States, adopted and promulgated by the American Law Institute in 1986, provides: “A state victim of a violation of an international obligation by another state may resort to countermeasures that might otherwise be unlawful, if such measures … (b) are not out of proportion to the violation and the injury suffered.” 
The American Law Institute, Restatement Third. Restatement of the Foreign Relations Law of the United States, American Law Institute Publishers, St. Paul, § 905.
Kalshoven
Kalshoven states:
[The requirement of proportionality] … can be clarified to a certain degree. In particular, it can confidently be stated that the proportionality envisaged here is proportionality to the preceding illegality, not to such future illegal acts as the reprisal may (or may not) prevent. Expectations with respect to such future events will obviously play a part in the decision-making process; thus, a prognosis that the enemy, unless checked, will commit increasingly grave breaches of the laws of war, will tend to make the reaction to the breaches already committed still more severe. Whilst, however, this psychological mechanism may be of interest from the point of view of theories of escalation, it cannot influence a legal judgement of the retaliatory action, which can take account only of its proportionality to the act against which it constitutes retaliation.
Furthermore, it can be stated with equal confidence that proportionality in this context means the absence of obvious disproportionality, as opposed to strict proportionality. In other words, belligerents are left with a certain freedom of appreciation; a freedom which in law is restricted by the requirement of reasonableness, but which in practice can easily lead to arbitrariness and excessive reactions … But … in the absence of a more precise rule … there is no alternative but to accept the flexibility and relative vagueness of the requirement of proportionality. 
Frits Kalshoven, Belligerent Reprisals, A. W. Sijthof, Leyden, 1971, pp. 341–342; see also Christopher Greenwood, “The Twilight of the Law of Belligerent Reprisals”, Netherlands Yearbook of International Law, Vol. 20, 1989, pp. 43–45, with more references.