Practice Relating to Rule 145. Reprisals

No data.
ILC Draft Articles on State Responsibility
Article 52 of the 2001 ILC Draft Articles on State Responsibility, entitled “Conditions relating to resort to countermeasures”, states:
1. Before taking countermeasures, an injured State shall:
(a) Call on the responsible State … to fulfil its obligations under Part Two [Articles 28–41];
(b) Notify the responsible State of any decision to take countermeasures and offer to negotiate with that State.
2. Notwithstanding paragraph 1(b), the injured State may take such urgent countermeasures as are necessary to preserve its rights. 
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 52.
Australia
Australia’s Defence Force Manual (1994) states: “Some nations may not comply with LOAC in the conduct of armed conflict. Where this occurs, and all methods of persuasion and diplomatic pressure have failed, reprisals may be justified but only against military objectives.” It adds: “In any case, reprisals must … only be resorted to after lesser forms of redress have been tried.” 
Australia, Manual on Law of Armed Conflict, Australian Defence Force Publication, Operations Series, ADFP 37 – Interim Edition, 1994, § 1310; see also Law of Armed Conflict, Commanders’ Guide, Australian Defence Force Publication, Operations Series, ADFP 37 Supplement 1 – Interim Edition, 7 March 1994, §§ 1210 and 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] … The victim of a violation must first exhaust other reasonable means of securing compliance before reprisals can be justified. 
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: “2) attempts must first be made to stop [the violation of the LOAC by the adversary] or to prevent its repetition by peaceful means”. 
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: … a prior warning is given”. 
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) provides:
To qualify as a reprisal, an act must satisfy the following conditions:
c. There must be reasonable notice that reprisals will be taken. What degree of notice is required will depend upon the particular circumstances of each case. Notice is normally given after the violation but may, in appropriate circumstances, predate the violation. An example of notice is an appeal to the transgressor to cease its offending conduct and punish those responsible. Thus, such an appeal may serve both as a plea for compliance and a notice to the adversary that reprisals will be undertaken;
d. The victim of a violation must first exhaust other reasonable means of securing compliance in order to justify taking a reprisal. 
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”:
1. In the event of serious or persistent breaches of the LOAC it may be necessary for the adverse party to resort to a reprisal in an attempt to terminate the illegality. [A] reprisal is an illegal act resorted to after the adverse party has performed illegal acts and has refused to stop after being called upon to do so.
6. To qualify as a reprisal, an act must satisfy the following conditions:
c. There must be reasonable notice that reprisals will be taken. What degree of notice is required will depend upon the particular circumstances of each case. Notice is normally given after the violation but may, in appropriate circumstances, predate the violation. An example of notice is an appeal to the transgressor to cease its offending conduct and punish those responsible. Thus, such an appeal may serve both as a plea for compliance and a notice to the adversary that reprisals will be undertaken;
d. The victim of a violation must first exhaust other reasonable means of securing compliance in order to justify taking a reprisal. 
Canada, The Law of Armed Conflict at the Operational and Tactical Levels, Office of the Judge Advocate General, 13 August 2001, § 1507.1 and 6.c–d.
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: … advance warning is given”. 
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:
As reprisals violate the law of war in response to a breach of that law committed by the enemy, they must be the last resort in order to restore respect for the law of war. Consequently, to carry out reprisals, a formal prior warning must be issued. 
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 a reprisal is that it is a “last resort” and that “prior warning” be given. 
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:
3. When circumstances permit, reprisal must be preceded by a demand for redress by the enemy of his unlawful acts.
5. Reprisal must only be used as a last resort when other enforcement measures have failed or would be of no avail. 
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.
France
France’s LOAC Manual (2001) states that reprisals must always be preceded by a warning. 
France, Manuel de droit des conflits armés, Ministère de la Défense, Direction des Affaires Juridiques, Sous-Direction du droit international humanitaire et du droit européen, Bureau du droit des conflits armés, 2001, p. 109.
Germany
Germany’s Military Manual (1992) provides: “Reprisals … shall be the last resort, if all other means to stop the illegal behaviour have failed and the warning has not been heeded.” 
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 a reprisal is that it is a “last resort” and that “prior warning” be given. 
Hungary, A Hadijog, Jegyzet a Katonai, Föiskolák Hallgatói Részére, Magyar Honvédség Szolnoki Repülötiszti Föiskola, 1992, p. 35.
Indonesia
Indonesia’s Air Force Manual (1990) provides:
In principle, reprisals in warfare are prohibited, i.e. an act which categorize[s] against the laws of war and aim[s] to [answer to] the breach of the laws of war treaties committed by the adverse party. The reprisal could be allowed if, although it has been warned, the adverse party still continue[s] to violate the laws of war. 
Indonesia, The Basics of International Humanitarian Law in Air Warfare, Indonesian Air Force, 1990, § 15(c).
Kenya
Kenya’s LOAC Manual (1997) states that reprisals “can only be taken if … prior warning is given”. 
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 lists that “it must first have been tried to stop the violation of humanitarian law of war by other means (for example by the intervention of a protecting power)”. 
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:
- an attempt must first be made to stop the breach of the humanitarian law of war in some other way (e.g., by intervention of the protecting power). 
Netherlands, Humanitair Oorlogsrecht: Handleiding, Voorschift No. 27-412, Koninklijke Landmacht, Militair Juridische Dienst, 2005, § 0423.
New Zealand
New Zealand’s Military Manual (1992) states:
(c) There must be reasonable notice that reprisals will be taken. What degree of notice is required will depend on the particular circumstances of each case. Notice is normally given after the violation but may, in appropriate circumstances, predate the violation. An example of notice is an appeal to the transgressor to cease its offending conduct and punish those responsible. Thus, such an appeal may serve both as a plea for compliance and a notice to the adverse Party that reprisals will be undertaken.
(d) The victim of a violation must first exhaust other reasonable means of securing compliance in order to justify taking reprisal. 
New Zealand, Interim Law of Armed Conflict Manual, DM 112, New Zealand Defence Force, Headquarters, Directorate of Legal Services, Wellington, November 1992, § 1606(4)(c) and (d).
Peru
Peru’s IHL Manual (2004) states:
(3) Reprisals may only be taken as a last resort to enforce international humanitarian law and make the enemy comply with its provisions.
(4) A formal warning must be given to the enemy, notifying it of the action that will be taken if it continues to commit or repeats its violations of international humanitarian law. 
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.(3) and (4).
Peru
Peru’s IHL and Human Rights Manual (2010) states:
(3) Reprisals may only be taken as a last resort to enforce international humanitarian law and make the enemy comply with its provisions.
(4) A formal warning must be given to the enemy, notifying it of the action that will be taken if it continues to commit or repeats its violations of international humanitarian law. 
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)(3)–(4), p. 234.
South Africa
South Africa’s LOAC Manual (1996) states: “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:
- Other reasonable means to secure compliance must have been undertaken and have failed (last resort).
- There must be reasonable warning that reprisals will be taken unless the illegal acts are stopped. 
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), in the chapter dealing with the exercise of command and its restrictions with regard to reprisals, states: “Reprisals must be the ultimate resort to re-establish respect for the law of war and may not lose sight of this aim.” 
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, § 2.3.b.(6).
In the chapter dealing with methods of combat, the manual lists among the conditions which must be fulfilled for the lawful taking of reprisals that “they must be a last resort to re-establish respect for the laws of war”; that the State which takes reprisals “has unsuccessfully tried to make the enemy respect the law of war or that such attempts would be of no use”; and that the enemy has been formally warned of the measure that would be taken if it failed to comply with or repeated its violations of the law of war. 
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).
Spain
Spain’s LOAC Manual (2007) states: “Reprisals can only be used as a last resort to make the enemy comply with the law of armed conflict”. 
Spain, Orientaciones. El Derecho de los Conflictos Armados, Tomo 1, Publicación OR7–004, (Edición Segunda), Mando de Adiestramiento y Doctrina, Dirección de Doctrina, Orgánica y Materiales, 2 November 2007, § 2.3.b.(6).
Togo
Togo’s Military Manual (1996) states that reprisals “may only be used if: … a prior warning is given”.  
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 can be used as a last resort measure”. 
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:
An infraction of the laws of war having been definitely established, every effort should first be made to detect and punish the actual offenders. Only if this is impossible may recourse be had to reprisals, if the injured belligerent is of the opinion that the facts warrant them. As a rule, the injured party must not at once resort to reprisals, but must first lodge a complaint with the enemy (or with a neutral Power, for transmission to the enemy) with a view to preventing any repetition of the offence and to securing the punishment of the guilty. This course should always be pursued unless the safety of the troops requires immediate drastic action and the persons who actually committed the offences cannot be secured. 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, § 646.
United Kingdom of Great Britain and Northern Ireland
The UK LOAC Pamphlet (1981) states that reprisals can only be taken if “prior warning is given”. 
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(b).
United Kingdom of Great Britain and Northern Ireland
The UK LOAC Manual (2004) states:
16.17. In order to qualify as a legitimate reprisal, an act must comply with the following conditions when employed:
b. It must be for the purpose of compelling the adversary to observe the law of armed conflict. Reprisals serve as an ultimate legal sanction or law enforcement mechanism. Thus, if one party to an armed conflict breaches the law but then expresses regret, declares that it will not be repeated and takes measures to punish those immediately responsible, then any action taken by another party in response to the original unlawful act cannot be justified as a reprisal;
c. Reasonable notice must be given that reprisals will be taken. What degree of notice is required will depend upon the particular circumstances of the case;
d. The victim of a violation must first exhaust other reasonable means of securing compliance before reprisals can be justified. 
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:
Priority to Other Remedies. Other measures of securing compliance with the law of war should normally be exhausted before resort is had to reprisals. This course should be pursued unless the safety of the troops requires immediate drastic action and the persons who actually committed the offences cannot be secured. Even when appeal to the enemy for redress has failed, it may be a matter of policy to consider, before resorting to reprisals, whether the opposing forces are not more likely to be influenced by a steady adherence to the law of war on the part of their adversary. 
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(b).
The manual adds: “Reprisals are never adopted merely for revenge, but only as an unavoidable last resort to induce the enemy to desist from unlawful practices.” 
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(d).
United States of America
The US Air Force Pamphlet (1976), in explaining reprisals, states:
(a) The action is taken in the last resort, in order to prevent the adversary from behaving illegally in the future.
(c) In order to be considered a reprisal, an act must have the following characteristics when employed:
(3) There must be reasonable notice that reprisals will be taken. What degree of notice is required will depend upon the particular circumstances of each case. Notice is normally given after the violation but may, in appropriate circumstances, predate the violation. An example of notice is an appeal to the transgressor to cease its offending conduct and punish those responsible. Thus, such an appeal may serve both as a plea for compliance and a notice to the adversary that reprisals will be undertaken.
(4) Other reasonable means to secure compliance must be attempted. The victim of a violation in order to justify taking a reprisal must first exhaust other reasonable means of securing compliance. This may involve appeals or notice … Finally, even if an appeal or other methods fail, reprisals should not be undertaken automatically since there are various other factors governing their employment. 
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(a) and (c).
United States of America
The US Air Force Commander’s Handbook (1980) states: “The taking of reprisals should be preceded by a request for redress of the wrong.” 
United States, Air Force Pamphlet 110-34, Commander’s Handbook on the Law of Armed Conflict, Judge Advocate General, US Department of the Air Force, 25 July 1980, § 8-4(b)(2).
United States of America
The US Naval Handbook (1995) provides:
To be valid, a reprisal action must conform to the following criteria:
3. When circumstances permit, reprisal must be preceded by a demand for redress by the enemy of his unlawful acts.
5. Reprisal must only be used as a last resort when other enforcement measures have failed or would be of no avail. 
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 US Naval Handbook (2007) states:
To be valid, a reprisal action must conform to the following criteria:
3. When circumstances permit, reprisal must be preceded by a demand for redress by the enemy of its unlawful acts.
5. Reprisal must only be used as a last resort when other enforcement measures have failed or would be of no avail. 
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: “Before they undertake reprisals, the armed forces of the SFRY [Socialist Federal Republic of Yugoslavia] shall try to force the enemy to respect the laws of war by means of other methods for preventing violations of such laws.” 
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 Hass and Priebke case in 1997, the Military Tribunal of Rome stated that, according to the unanimous views of writers, reprisals were legitimate only when they appeared as the only possible reaction because all possible means of identification and capture of the author of the unlawful act had been exhausted. 
Italy, Military Tribunal of Rome, Hass and Priebke case, Judgment in the Trial of First Instance, 22 July 1997, Section 4.
In its relevant parts, this judgment 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, reprisals were admitted only as a measure of last resort. 
Netherlands, Special Court (War Criminals) at The Hague, Rauter case, Judgment, 4 May 1948.
United States of America
In its judgment in the List case (The Hostages Trial) in the late 1940s, the US Military Tribunal at Nuremberg, discussing the taking of hostages in occupied territories, noted: “The occupant is required to use every available method to secure order and tranquillity before resort may be had to the taking and execution of hostages.” However, the Tribunal had previously stated:
Where innocent individuals are seized and punished for a violation of the laws of war which has already occurred, no question of hostages is involved. It is nothing more than the infliction of a reprisal. Throughout the evidence in the present case, we find the term hostage applied where a reprisal only was involved. 
United States, Military Tribunal at Nuremberg, List case (The Hostages Trial), Judgment, 8 July 1947–19 February 1948.
Australia
The Report on the Practice of Australia states: “Australia’s opinio juris is, with certain exceptions, supportive of a prohibition against belligerent reprisals.” It adds, however: “Australian opinio juris does not consider that exceptions to the prohibition against reprisals, where these represent measures of last resort, will place it in breach of its customary obligations.” 
Report on the Practice of Australia, 1997, Chapter 2.9.
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:
(a) that the Party victim of the breach clearly has no means of putting an end to the breach other than by considering recourse to reprisals,
(c) that the Party responsible for the violation shall be given due warning that such measures will be taken if the violation is continued or renewed. 
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:
2.The measures [which are designed to repress the breaches of and induce compliance with the Protocol] may be taken only when the following conditions are met:
(a) The measures may be taken only when other efforts to induce the adverse Party to comply with the law have failed or are not feasible, and the victimized Party clearly has no other means of ending the breach;
(c) The Party committing the breach must be given specific, formal, and prior warning that such measures will be taken if the breach is continued or renewed. 
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.
Netherlands
During discussions on reprisals at the CDDH, the representative of the Netherlands stated that “reprisals were a very questionable means of securing respect for humanitarian law”. He also said that his delegation felt that “reprisals should remain a measure of last resort”. 
Netherlands, Statement at the CDDH, Official Records, Vol. IX, CDDH/I/SR.48, 30 April 1976, p. 86, § 14.
Netherlands
In an explanatory memorandum submitted to the Dutch Parliament in the context of the ratification procedure of the 1977 Additional Protocols, the Government of the Netherlands stated that for a reprisal to be lawful “the taking of the reprisal as such must be announced [and] other attempts to force the other party to comply with international law must have failed”. 
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 a 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 … 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 a 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 … a means of last resort.” 
United Kingdom, Written statement submitted to the ICJ, Nuclear Weapons case, 16 June 1995, p. 58.
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 this would be true “only after [a] formal warning to the adverse party requiring cessation of the violations has been disregarded”. 
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 stated: “Reprisals are permitted under the laws of war … only after other means of achieving this objective [i.e. “the limited purpose of compelling the other belligerent to observe the laws of war”] have been exhausted (including diplomatic protest).” 
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 a 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 … other means of securing compliance [of the enemy with the law of armed conflict] should be exhausted … 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 the responsibility of States for internationally wrongful acts, to which the 2001 ILC Draft Articles on State Responsibility, and thus Article 52 entitled “Conditions relating to resort to countermeasures”, 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: “A reprisal is an otherwise illegal act resorted to after the adverse party has himself indulged in illegal acts and refused to desist therefrom after being called upon to do so.”  
UN Commission of Experts established pursuant to Security Council Resolution 780 (1992), Final report, UN Doc. S/1994/674, 27 May 1994, §§ 63–64.
No data.
No data.
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 whereby they must be a last resort in attempts to impose compliance by the adversary with legal standards (which entails, amongst other things, that they may be exercised only after a prior warning has been given which has failed to bring about the discontinuance of the adversary’s crimes). 
ICTY, Kupreškić case, Judgment, 14 January 2000, § 535.
Special Arbitral Tribunal
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 that “reprisals … are an act carried out – after an unfulfilled demand” and that “reprisals are only lawful when preceded by an unsatisfied demand. The use of force is only satisfied by its character of necessity.” 
Special Arbitral Tribunal, Naulilaa case, Decision, 31 July 1928, pp. 1026–1027.
No data.
Kalshoven
Kalshoven states:
The requirement of subsidiarity has generally been taken to mean that recourse to belligerent reprisals is an exceptional measure which must be regarded as an ultimate remedy, after other available means of a less exceptional character have failed. Applying this criterion to inter-State belligerent reprisals (as opposed to State-to-population or quasi-reprisals), it would imply that protests, warnings appeals to third parties and other suitable means must have remained without effect, or so obviously been doomed to failure that there was no need to attempt them first. Nor is this an unreasonable requirement even in time of war: the practice of belligerents shows a frequent recourse to such comparatively innocent means as protests, appeals to international public opinion, complaints lodged with appropriate international bodies, threats to punish individual war criminals, and so on. Indeed, it would seem that in no instance have belligerent reprisals been taken without previous attempts to obtain satisfaction in other ways, or in any event without its having been considered that these would have been possible. However, on theoretical considerations the possibility cannot be excluded of situations where the fruitlessness of any other remedy but reprisals is apparent from the outset. In such exceptional situations, too, recourse to reprisals can be regarded as an ultimate remedy and, hence, as meeting the requirement of subsidiarity. 
Frits Kalshoven, Belligerent Reprisals, A. W. Sijthof, Leyden, 1971, p. 340.
Greenwood
Greenwood notes: “Reprisals are a subsidiary means of redress and thus should be used only as a last resort. This principle is often expressed in terms of a requirement that a State must actually employ all other methods of securing redress before recourse is had to reprisals.” With regard to the exceptional cases referred to by Kalshoven, he states:
While the availability of other sanctions for violations of the law of armed conflict should not be underestimated, it is likely that there will be occasions when the possibility to which Kalshoven refers will be more than theoretical … However, the use of reprisals in an armed conflict is such a serious step and may have such disastrous consequences that the requirement that all reasonable steps be taken to achieve redress by other means before reprisals are ordered is probably one which should be strictly insisted upon, unless delay will endanger the safety of troops or civilians. 
Christopher Greenwood, “The Twilight of the Law of Belligerent Reprisals”, Netherlands Yearbook of International Law, Vol. 20, 1989, p. 47.