The applicability and relevance of the law of armed conflict

When the use of force goes beyond self-defence and crosses the threshold into aimed conflict the potential exists for much more destructive and widespread use of force. The limitations on the use of force are much reduced in an aimed conflict. On the one hand there is an imperative to apply the laws of aimed conflict because of their protective provisions in respect of prisoners, civilians, the wounded, sick and shipwrecked, cultural property and so on. These protective rules only exist, however, because the rules for the


See Rule 47 ‘Enemy Vessels Exempt from Attack’ in Louise Doswald-Beck (ed), San Remo Manual on International Law Applicable to Armed Conflicts at Sea (Cambridge University Press, 1995) (‘San Remo Manual1)

use of force in an armed conflict are so permissive. It is possible to target enemy warships, military aircraft and naval auxiliaries at sea, and military targets and personnel ashore offensively, that is to say, without waiting for a threat or use of force from those targets.11 The limitations of self-defence do not apply. Crossmg from the defensive use of force in peace time into the offensive use of force in an aimed conflict is therefore the crossmg of a maj or threshold. The limitations of necessity and proportionality that should apply in any resort to force in international relations (that is, within the jus ad belluni) do not apply in the same way to the law of aimed conflict (the jus in belief Once the law of aimed conflict applies, as history has shown, it is much harder to argue that a military target is an unlawful target.[1]

Where a state, or states, deliberately resorts to the use of military force, with the expectation that a state of aimed conflict should then exist, then the law of aimed conflict should apply. Examples of this would include the Gulf War in 1991 or the Falklands/ Malvinas conflict in 1982. However, a particular incident may be localised to a warship or military aircraft or a small group of them, as discussed in many of the cases previously, with no broader conflict in contemplation. This strongly suggests that the use of force in navigational incidents should be limited by the peacetime law of self-defence as much as possible so as to prevent a major escalation in

Proportionality 53 conflict.[2] Such an approach may have implications for the status of those who are captured, as discussed subsequently with regard to the Kerch Strait Case but would not lower requirements relating to the protection of civilians, the wounded, sick and shipwrecked, cultural properly and so on. This is a distinct argument in favour of the more limited unit self-defence approach to the law of self-defence in its application to warships. This approach reflects the cases discussed in Chapter 1.

The cases

Oil platforms case

In the Oil Platforms Case, despite quite a significant engagement between US and Iranian forces in Operation Praying Mantis, both the majority and separate opinions treated the issue as governed by the international law of self-defence and not the law of armed conflict. This appears to have followed from Iran bringing its claim as a breach of the Treaty’ of Amity discussed in Chapter 1. Even so, this case places the threshold of application for the law of armed conflict quite high. Iran lost half of its surface fleet to US action. Despite the language of ‘legitimate military target’ as discussed previously, so far as it went, there seemed to be no suggestion in the case that it would have been permissible to conduct offensive targeting of opposing forces beyond the immediate area of operations, such as ashore in Iran. The use of force was limited to that required in self-defence of particular units.


By way of contrast, in the Nicaragua Case the Court clearly stated that the law of armed conflict applied to the US mining of Nicaraguan waters.

The Court observes that Nicaragua, which has invoked a number of multilateral treaties, has refrained from making reference to the four Geneva Conventions of 12 August 1949, to which both Nicaragua and the United States are parties . . . The actions of the United States in and against Nicaragua fall under the legal rules relating to international conflicts ... Article 3 which is common to all four Geneva Conventionsof 12 August 1949 defines certain rules to be applied in the armed conflicts of a non international character . . . they are rules which, in the Court’s opinion, reflect what the Court in 1949 called ‘elementary considerations of humanity’ {Corfu Channel p. 22).[3]

The action of deliberately mining foreign territorial waters is quite different to the immediate defence of a warship in a navigational incident. It is understandable that the Court would apply the law of aimed conflict to deliberate mining. This illustrates the type of action and intention required for the law of aimed conflict to apply.

South China Sea Arbitration - the Second Thomas Shoal incidents

hi the South China Sea Arbitration, the incidents concerned Chinese attempts to deny resupply by the Philippines to its marines aboard a naval landing craft, BRP Sierra Madre, permanently grounded on Second Thomas Shoal. The Award described the incident in similar terms to the Scarborough Shoal incidents to be discussed in Chapter 4, with Chinese vessels trying to impede the passage of the Philippine vessels. In the first incident, on 9 March 2014, the Chinese vessels succeeded in blocking a Philippine attempt to proceed to the Shoal, before later at least giving warnings by means of sirens, megaphones and digital signboards to prevent subsequent attempts. A machinery breakdown led to the two Philippine vessels departing the area. After a resupply of the marines by air, a later incident on 29 March 2014 led to blocking and evasion manoeuvres at speed again. The Philippine Bureau of Fisheries and Aquatic Resources vessel used its shallower draft to evade the Chinese vessels and effect the resupply and rotation of the marine garrison. On this occasion the Chinese vessels did reportedly give warnings by means of whistle and some form of unspecified communication in words, requiring the Philippine vessel to turn around.

In line with the Corfu Channel Case and Oil Platforms Case, the Arbitral Tribunal in the South China Sea Arbitration dealt with the whole situation according to peacetune rules. The Tribunal determined that Second Thomas Shoal was a low-tide elevation in the Philippine exclusive economic zone, therefore no questions arose as to navigational rights within territorial or internal waters.[4] The Tribunal assessed that it had no jurisdiction in respect of the incidents as they concerned a ‘quintessentially military' situation’. The incidents were therefore excluded under article 298(1 )(b) of the 1982 Convention, as China chose not to accept jurisdiction over disputes concerning military activities when it ratified the Convention. Even so, despite finding that it was a military situation, there was no suggestion of the law of armed conflict applying.

Kerch Strait Case

The decision in the Kerch Strait Case is the closest there is to a judicial exposition on the application of the law of armed conflict to navigational incidents involving warships. The Tribunal stated the Ukrainian claim as follows:

31. According to Ukraine, the three naval vessels had departed from the ‘port of Odesa’, in the Black Sea, and their mission was to transit, through the Kerch Strait, to the port of Berdyansk in the Sea of Azov. Ukraine further states that,

[a]s they approached the entrance to the Kerch Strait on the night of 24/25 November, the vessels received radio communications from the Russian Coast Guard - a division of the Border Service of the Federal Security Service (‘FSB’) - asserting that the Strait was closed.

When the Ukrainian vessels proceeded to the strait on 25 November 2018, they were blocked by Coast Guard vessels of the Russian Federation. The Ukrainian vessels later turned around and navigated away from the Kerch Strait but were pursued by the Coast Guard vessels. During the pursuit, one Coast Guard vessel fired at the Berdyansk, wounding three members of its crew and causing damage to the vessel. In the following course of events, all three Ukrainian vessels and the servicemen on board were seized and detained by Coast Guard vessels of the Russian Federation. According to the Press Service of the FSB

(hereinafter ‘the FSB Press Service’) of 26 November 2018, the three vessels were ‘delivered to the port of Kerch' on 26 November 2018.[5]

Russia did not appear before the Tribunal but instead submitted a memorandum, which the Tribunal quoted as follows:

  • 32. According to the Memorandum submitted by the Russian Federation:
  • 21. On 26 and 27 November 2018, [the 24 Ukrainian servicemen] on board the vessels were formally apprehended under Article 91 of the Code of Criminal Procedure of the Russian Federation as persons suspected of having committed a crime of aggravated illegal crossmg of the State border of the Russian Federation (section 3 of Article 322 of the Criminal Code of the Russian Federation).
  • 22. By separate decisions of 27 and 28 November 2018 delivered by the Kerch City Court and the Kievskiy District Comt of Simferopol, the Military Servicemen were placed in detention. The investigation is still pending and on 17 April 2019, the Court [Lefortovo District Court of Moscow] extended the detention of the Military Servicemen until 24 July 2019.

As the proceeding concerned provisional measures and was not the final disposition of the substantive issues, the decision of the Tribunal does not provide a complete statement as to the threshold for the application of the law of armed conflict. At the time of writing, the substantive issues are before an arbitral tribunal formed under Annex VII of the Law of the Sea Convention (with the Permanent Court of Arbitration acting as registry). Russia has released both the vessels and the crew. Also, the question tinned on Russia’s exclusion of the jurisdiction of the Tribunal for ‘military activities’ under article 298(l)(b) of the Law of the Sea Convention, rather than just whether the law of aimed conflict applied as such. Even so, the ongoing conflict between Ukraine and Russia was relevant.

The decision of the Tribunal was that Russia’s actions constituted law enforcement action and not military activities. As stated previously, Russia’s

Proportionality 57 action was to enforce its border law, in respect of which it detained the crew of the Ukrainian vessels in order to conduct a criminal investigation against them. This then becomes a question of violation of the sovereign immunity of the Ukrainian naval vessels.[6] Whilst the Tribunal’s position makes some sense given Russia’s subsequent treatment of the matter as law enforcement, some judges provided separate opinions on this issue to the effect that, while they agreed with the provisional orders to release the three vessels and the 24 crew, they did not necessarily agree with the Tribunal’s treatment of the matter as one of law enforcement rather than military activities. Judge Gao distinguished between the initial phase of the incident. which involved Russia denying transit passage and the subsequent stand-off phase between the Ukr ainian and Rrtssian vessels over several hours and which resulted in the shooting at and apprehension of the Ukr ainian vessels. Judge Lijnzaad stated that the subsequent arbitral tribunal proceedings needed to look more closely at the applicability of the laws of armed conflict and whether the Tribunal actually has no jurisdiction, but that this went ‘well beyond the prinia facie analysis of a Request for Provisional Measures’. Judge Lucky favoured the view that the incident was a law enforcement exercise but, without hearing from Russia in support of its opposing contention, found it difficult to concur with a definitive finding that ‘such a dispute is not military in nature’. Judge Kolodkin did not agree with the orders of the Tribunal at all and provided persuasive arguments that Ukraine had stated there was an armed conflict between itself and Russia and that the crew were being held as prisoners of war. It could not hold this position and also claim that an action between vessels of the Ukrainian Navy on one hand, and the Russian Coast Guard and Navy on the other, over more than eight hours in which shots were fired and vessels and crew captured, could not be military' activities.

Ukrainian statements that the incident was part of an aimed conflict and Russia’s apprehension of the vessels and crew for a criminal investigation, despite putting contrary positions before the Tribunal, confuse the issues considerably.[7] It is possible still to conclude from this that the threshold for the application of the law of aimed conflict is high. Even after a naval engagement such as this, the Tribunal is not treating it as a matter for the law of naval warfare. Despite Russia claiming the military activities exemption from the jurisdiction of the Tribunal, even it is not arguing that the law of naval warfare applies. This suggests that it was not in the interests of either parly, or the Tribunal, to state that this threshold had been crossed, and that there can be a range of reasons why it might be undesirable to cross the threshold from a navigational incident to the law of naval warfare.

The manuals

hi stark contrast, a selection of law of aimed conflict or law of naval warfare manuals in English set a very low threshold for the application of the law of aimed conflict at sea. Most address the issue only briefly. For example, the German Navy Commanders ’Handbook: Legal Bases for Operations of 2005 states:

International humanitarian law will be applied to international aimed conflicts (the law of non-mtemational aimed conflict will not be addressed in this publication). Today, the meaning of this term is no longer limited to a war that has been declared or a state of war and the partial or complete military occupation of another state’s territory, but

Proportionality 59 extends to any international military confrontation. Therefore, to use a popular metaphor, all that is required is the firing of a first shot, that is the occurrence of a situation in which aimed engagements might cause casualties.[8]

The US Commander’s Handbook on the Law of Naval Operations of 2017 is even less specific:

As a matter of international law, application of the law of aimed conflict between belligerents does not depend on a declaration of war or other formal recognition, but on whether an ‘aimed conflict’ exists in fact, and if so, whether the aimed conflict is of an ‘international’ or ‘ non-international ’ character.

It does though helpfully state that ‘it is important for commanders to understand [that].. . the legality of a State’s decision to resort to war is primarily the responsibility of its political leadership’.

The manuals generally see the threshold for the application of the law of aimed conflict as a question of fact, rather than law, which is to say that the use of aimed force is actually occurring. A key reference is the San Remo Manual on International Law Applicable to Armed Conflicts at Sea (‘San Remo Manual'), which is a statement of the law produced by a roundtable of experts in 1994 to address the development of the law of the sea and the law of aimed conflict, since the conclusion in 1907 of most of the treaties specifically addressed to naval warfare. It is the most widely accepted statement of the law of naval warfare, and states the threshold for the application of the laws of naval warfare in its first two rules as follows:

  • 1 The parties to an aimed conflict at sea are bound by the principles and rules of international humanitarian law from the moment aimed force is used.
  • 2 In cases not covered by this document or by international agreements, civilians and combatants remain under the protection and authority of the principles of international law derived from established custom, from the principles of humanity and from the dictates of the public conscience.

This is a very low threshold. The manual does, however, then go straight on to address the issue of self-defence. Given the significance of the manual it is worth reproducing in full:

Section II: armed conflicts and the law of self-defence

  • 3 The exercise of the right of individual or collective self-defence recognized in Article 51 of the Charter of the United Nations is subject to the conditions and limitations laid down in the Charter, and arising from general international law. including in particular the principles of necessity and proportionality.
  • 4 The principles of necessity and proportionality apply equally to armed conflict at sea and require that the conduct of hostilities by a State should not exceed the degree and kind of force, not otherwise prohibited by the law of armed conflict, required to repel an armed attack against it and to restore its security.
  • 5 How far a State is justified in its military' actions against the enemy will depend upon the intensity and scale of the armed attack for which the enemy is responsible and the gr avity of the threat posed.
  • 6 The rules set out in this document and any other rules of international humanitarian law shall apply equally to all parties to the conflict. The equal application of these rules to all parties to the conflict shall not be affected by the international responsibility that may have been inclined by any of them for the outbreak of the conflict.49

This approach places emphasis on the protective nature of the rules while at the same time trying to limit the scope of conflicts. These aims are clearly in tension as the rest of the rules pennit offensive targeting of enemy units. The manual does not develop how the jus ad belluni requirements of rules 3 to 6 should actually limit the other rules. This seems to be a matter for governments, removing the question from unit and task group commanders to make the decisions to use force. Even if some of the rules are quite clear, the Explanation to the San Remo Manual is more equivocal, notably:

4.5 The application of the principles set out in paragraph 4 was the subject of some further controversy. The disagreement centred on whether the principles of necessity and proportionality are applicable in a strategic sense only, or also on a tactical level. Those in favour of the latter approach thought that the application of the principles of necessity andproportionality could affect hostilities at all levels of the conflict in that they would restrict the choice of targets, the use of methods and means of warfare and measures taken against neutral shipping taken not only in accordance with the rules of international humanitarian law, but also in accordance with whether they would be necessary and proportionate to the needs of self-defence of the parties. Those participants who were not in favour of this approach were of the opinion that the principles of necessity and proportionality cannot affect tactical behaviour once an action in self-defence has commenced and that these principles rather only affect strategic decisions on how to achieve the needs of self-defence.[9]

On the first view, the law of naval warfare applies at a low threshold but is also limited by jus ad bellum considerations of necessity and proportionality in self-defence in the selection of targets and interference with neutral shipping. On the second view,jus ad bellum considerations do not limit the application law of naval warfare at the tactical level. The latter view appears to accord more closely to the cases discussed previously. It is not for unit or task group commanders to decide to expand, or contract, the parameters for the use of force in a navigational incident by applying, or limiting the application of, the law of naval warfare. This is a decision for governments. Consistently with the concept of unit self-defence, commanders may defend their units but may not decide themselves that the law of armed conflict applies and engage targets accordingly. This approach would also be consistent with the words of the International Committee for the Red Cross/ Red Crescent Commentary on the Geneva Conventions cited in the Explanation to the San Remo Manual in relation to Rule 1 that:

Any difference arising between two States and leading to the intervention of members of the armed forces is an aimed conflict within the meaning of Article 2, even if one of the Parties denies the existence of a state of war. [emphasis added]

The difference is between states, not tactical commanders. The application of the law of aimed conflict therefore is not a decision for such commanders, it is for the governments of states. This may not have been the intention of the authors of the ICRC Commentary or the Explanation to the San Remo Manual, but it is one way of reconciling the differing views.

Of the manuals examined, the New Zealand Manual of Armed Forces Law, Volume 4, Law of the Armed Conflict is closest to the position that the existence of an aimed conflict is primarily a question for states:

Since much of international law is founded on the practice of States, the question of whether a conflict exists is still, to a large degree, to be decided by the State or States most affected.[10]

There can be military actions which fall below the threshold of aimed conflict:

Aimed conflict exists where there is deliberate, organised and sustained aimed violence. No set number of casualties, level of damage or duration is determinative. Fleeting military encounters that cause few casualties and little damage, however, are seldom recognised by the parties involved as aimed conflict. The fundamental rules of LOAC, such as those protecting persons deprived of their liberty in such engagements, must still be complied with.

On the other hand, the United Kingdom Manual of the Law of Armed Conflict (UK Manual) reflects the approach in the San Remo Manual. It only states that ‘The law of aimed conflict applies in all situations when the aimed forces of a state are in conflict with those of another state’. In the context of incidents involving warships that is a veiy low threshold. The UK Manual does, though, helpfully emphasise the question of proportionality in relation to maritime conflicts. It refers these matters back to the Ministry of Defence, not leaving them to unit or task group commanders. It is reasonably clear therefore that, whilst questions of self-defence can be for unit or task group commanders, questions of the application of the law of aimed conflict are for governments (even if they are questions of fact and not law). Notably, the relevant paragraph states that, for reasons of proportionality, in action against neutral vessels and aircraft a belligerent may be more restrained than the rules of naval warfare described in the chapter might suggest. In giving this example, the UK Manual does not expressly limit the action that may be taken against a hostile belligerent. It does, though, convey that jus ad bellum necessity and proportionality considerations are an overall limitation in a conflict of limited scope, which should include a navigational incident involving warships.


It is possible therefore to argue that the threshold of application of the law of aimed conflict at sea is actually quite high. It is unlikely to apply to incidents involving the navigation of warships where there is no intention to engage in a broader conflict. This could be the case even where there is significant loss of life and destruction of vessels, aircraft or installations. This position distinguishes between decisions to use force made at the level of unit or task group commanders and those made by governments. Therefore, the use of force in navigational incidents - as opposed to broader, intentional, conflicts between states, as expressed in the Caroline Principles - is that which is necessary and proportional for the immediate defence of the warship or coastal installation. Targeting of opposing military forces which do not pose an immediate threat is then not lawful. Decisions as to national self-defence and the application of the law of aimed conflict, particularly the broader targeting of opposing forces which do not pose an immediate threat to a warship, task group or vessels under escort, are for governments rather than commanders on the scene.

  • [1] See, ibid., Part III ‘Basic Rules and Target Discrimination’ 2 The controversy over the sinking of the Argentinian cruiser General Belgrano by a British submarine in 1982 illustrates the point. The debate was whether the ship was a lawful target wherever it was on the high seas during that war or only once it had entered the Bntish-declared 200 nautical mile total exclusion zone, see ‘Annex to Prime Minister’s letter to George Foulkes, Esq. MP dated 19.9.84’ later published in Hansard, Open Parliament Licence to_George_Foulkes,_Esq._MP_dated_19.9.84; see also Dieter Fleck, ‘Rules of Engagement for Maritime Forces and the Limitation of the Use of Force Under the UN Charter’ (1988) 31 German Yearbook of International Law 165, 173; Ken Booth, Law, Force and Diplomacy at Sea (1985, Routledge Revivals, 2014) 161; Judith Gardam, Necessity, Proportionality! and the Use of Force by States (Cambridge, 2004) 171; the state of hostilities subject to an armistice with North Korea has also created difficulties in calibrating a proportionate response to warlike acts, notably including the seizure by North Korea of the electromc surveillance ship USS Pueblo in 1968, DP O’Connell, The Influence of Law on Sea Power (Naval Institute Press, 1975) 65, and the sinking of the RKS Chenoan, presumably by North Korea, in 2010, see ‘Letter dated 4 June 2010 from the Permanent Representative of the Republic of Korea to the United Nations addressed to the President of the Security Council’ UN Doc S/2010/281 3 San Remo Manual 182, 197, 223; see David Letts, ‘A Review of Selected Measures for Reducing Potential Conflict Among Naval Vessels in the South China Sea’ in Jorg Schildknecht, Rebecca Dickey, Martin Fink and Lisa Fems (eds), Operational Law in International Straits and Current Maritime Security Challenges (Springer International Publishing, 2018) 143, 149
  • [2] See Letts, ibid. 146-148, 150, 156 2 Oil Platforms Case 198-199 3 Ibid. 194 4 Nicaragua Case 102, at least in customary international law
  • [3] Ibid. 103-104 2 South China Sea Arbitration 442; for a Chinese perspective on this incident, and others not directly discussed in this book, see Nong Hong, ‘Law Enforcement in a Disputed Maritime Zone: A Political and Legal Analysis’ in Shicun Wu and Keyuan Zou (eds), Arbitration Concerning the South China Sea: Philippines versus China (Ashgate Publishing, 2016) 223-225; see Cameron Moore, ‘The Arbitral Award in the Matter of the South China Sea Between the Philippines and China - The Use of Force and Freedom of Navigation’ (2017) Asia Pacific Journal of Ocean Law and Policy 117,123-124 3 South China Sea Arbitration 442-443 4 Ibid. 444-445 5 Ibid. 6 Ibid.
  • [4] South China Sea Arbitration 256,453 2 Ibid. 456
  • [5] Kerch Strait Case 9 2 Ibid. 10 3 Ibid, and see 4 'Russia returns nary vessels seized from Ukraine’ Deutsche Wette (online), 18 November 2019 5 Kerch Strait Case 13-20 6 Ibid. 18 7 Ibid. 19-20
  • [6] Ibid. 27-2S 2 See also James Kraska, ‘Did ITLOS Just Kill the Military Activities Exemption in Article 298?’ EJIL Talk (online), 27 May 2019 and Yurika Ishii, ‘The Distinction Between Military and Law Enforcement Activities: Comments on Case Concerning the Detention of Three Ukrainian Naval Vessels (Ukraine v Russian Federation), Provisional Measures Order’ EJIL Talk (online), 31 May 2019 3 Kerch Strait Case, Separate Opinion of Judge Gao, 6-7 4 Ibid., Separate Opimon of Judge Lijnzaad, 2-3 5 Ibid., Separate Opimon of Judge Lucky, 5 6 Ibid., Dissenting Opimon of Judge Kolodkin, 6 7 Ibid. 5 and 7
  • [7] James Kraska, ‘The Kerch Strait Incident: Law of the Sea or Law of Naval Warfare?’ EJIL Talk (online), 3 December 2018 2 See Natalie Klein, Maritime Security and the Law of the Sea (Oxford University Press, 2011)270 3 Given the focus of this book on conflict between states it will not address non-state actors or non-mtemational aimed conflict, except to say that the law of naval warfare, as a specialised branch of the law of armed conflict, applies to conflict between states. The broader law of armed conflict, including the law applying to non-mtemational aimed conflicts and non-state actons, can apply in limited situations at sea, such as where naval units engage shore targets with naval gunfire support or close air support, ait 49(3) Additional Protocol T, see David Letts, ‘The Relevance of Australian Domestic Law to Naval Warfare’ in Dale Stephens and Matthew Stubbs (eds), The Law of Naval Warfare (Lexis Nexis, 2019) 339, 345; see also Rob McLaughlin, ‘Does the Law of Naval Warfare Apply to NIACs at Sea? Well, Sort of... ’ Stephens and Stubbs, ibid. 321, particularly as to whether the law of naval warfare is a subset of the law of aimed conflict, or rather a subset of the law of the sea which overlaps with the law of aimed conflict as it also includes the law of neutrality and prize law, 324-325
  • [8] 116 2 Para 5.2 3 Ibid. 5.1 4 n 10 5 Ibid. 61-62 6 4S Ibid. 7
  • [9] Ibid. 77 2 See also International Committee of the Red Cross, Convention (II) for the Amelioration of the Condition of Wounded, Sick and Shipwrecked Members of Armed Forces at Sea. Geneva, 12 August 1949: Commentary of 2017 nsf Comment .xsp?action=openDocument&documentId= 1A35EE65211A18AEC1258115 0044243A#78_B in which there is acknowledgement that some incidents may occur where there is no mtention to engage in armed conflict but there is nonetheless a strong preference for the application of the Convention at the lowest level of violence, paras 240, 259, 263-265
  • [10] Para 5.2.2 2 Para 5.2.6 3 United Kingdom Ministry of Defence, The Manual of the Law of Armed Conflict (Oxford University Press, 2004) 27 4 348-349
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