Territorial and internal waters

The use of force at sea does not just involve the law on the use of force. The law of the sea is fundamentally a system of maritime zones, within which rights and obligations vary. It is necessary to apply use of force rales to specific maritime zones and consider the differences they make to the use of force by or against warships. The limits of what might be permissible in self-defence will vary along a spectrum from a warship being in a foreign port to being on the high seas. Use of force may also be relevant to asserting passage, meaning that it may be necessary to clear an obstruction to the passage of a warship, which may take the form of mines, physical banders or even vessels. The extent to which such action would be justifiable at sea depends very much on the maritime zone. Obstructing a warship on the high seas is a different question to doing so in the territorial sea.

This chapter will deal with the territorial sea and internal waters, considering the case law and the histoiy of incidents. Tire Nicaragua Case described the sovereign nature of the territorial sea and internal waters as follows:

The Court should now mention the principle of respect for State sovereignty, which in international law is of course closely linked with the principles of the prohibition of the use of force and of non-intervention. The basic legal concept of State sovereignty in customary international law, expressed in, inter alia. Article 2, paragraph 1, of the United Nations Charter, extends to the internal waters and territorial sea of every State and to the air space above its territory

Territorial sea

Under article 3 of the 1982 Convention, the territorial sea may extend up to 12 nautical miles from the territorial sea baseline, which is normally the


Nicaragua Case 101

low water line along the coast[1] but can also include straight closing lines across the mouths of rivers, bays and deeply indented coastlines, as well as around fringing islands. Archipelagic states may claim a territorial sea measured from the straight baselines around the archipelago. The waters within the territorial sea, and archipelagic waters, are part of the sovereignty of the coastal state, subject to exercise of the right of innocent passage by foreign-flagged ships. There is no right of innocent passage for aircraft in the territorial sea or archipelagic waters, although there are rights of overflight for aircraft in international straits and archipelagic sea lanes.11

Innocent passage for warships

Some states do not accept that warships have a right of innocent passage without prior authorisation or notification. This was not a majority view at the Thud United Nations Conference on the Law of the Sea, however, and did not find its way into the text of the 1982 Convention. The 1982 Convention reflects the position in the Corfu Channel Case to the extent that warships have a customary international law right of innocent passage (at least through international straits). The view of the small number of states which purport to require prior notification or authorisation has particular implications for the perception of the presence of warships in the regions, and incidents, which are the focus of this book.

This begs two questions at least. The first is, what can a coastal state do to prevent non-innocent passage by a warship through the territorial sea? The second is, to what extent can a warship assert innocent passage through the territorial sea, particularly where a coastal state does not accept passage by a warship without prior notification or authorisation?

The second question is perhaps easier to address than the first. A warship has only a right of innocent passage in a foreign territorial sea. The 1982 Convention articulates the meaning of innocent passage at reasonable length, even if not with complete precision:

Article 19 Meaning of innocent passage

  • 1 Passage is innocent so long as it is not prejudicial to the peace, good order or security of the coastal State . . .
  • 2 Passage of a foreign ship shall be considered to be prejudicial to the peace, good order or security of the coastal State if in the territorial sea it engages in any of the following activities:
    • (a) any threat or use of force against the sovereignty, territorial integrity or political independence of the coastal State, or in any other manner in violation of the principles of international law embodied in the Charter of the United Nations;
    • (b) any exercise or practice with weapons of any kind:
    • (c) any act aimed at collecting information to the prejudice of the defence or security of the coastal State;
    • (e) the launching, landing or taking on board of any aircraft;
    • (f) the launching, landing or taking on board of any military device;
    • (j) the carrying out of research or survey activities;
    • (1) any other activity not having a direct bearing on passage.

Self-defence of warships in the territorial sea

If the coastal state requires a warship to leave by virtue only of the requirement for prior notification or authorisation, the warship could assert that it is conducting innocent passage as may the ships of all states[2] under article 17. If the coastal state uses force against the warship then the warship may defend itself. One view might be that use of force by the warship would render the passage non innocent, but this would undermine the right of innocent passage being available to ‘ships of all states’ and the reasoning in the Corfu Channel Case that it is lawfill to assert a right of passage. It should be contrary to the requirements in article 19, listed earlier, for the warship to do anything more in the territorial sea than defend itself, however.

Asserting passage in the territorial sea

Should the coastal state use vessels to create such an obstruction that it prevents a warship from navigating at all, then arguably the warship could shoulder the obstructing vessels out of the way as an act of self-defence or in order to get away from the territorial sea. However, to do so to keep the territorial sea open for passage more generally, or as part of escorting vessels through, would be contrary to the right of innocent passage. It is important to note that, unlike an international strait or archipelagic sea lane, the coastal state can temporarily close its territorial sea, so foreign warships trying to keep a territorial sea open to passage could not be exercising the right of innocent passage. This would be a threat or use of force. The remedy at this point for asserting the right of innocent passage could only be diplomatic or through international dispute resolution methods. It could not be operational.


The argument against clearing obstructions to assert passage in the territorial sea should apply to escorting civilian merchant vessels in the territorial sea as well. This is distinct from escorting vessels in international straits or archipelagic sea lanes, which is the subject of Chapter 5, or in international waters, which is the subject of Chapter 6. It is also not the same as warships in a task group, which may include merchant vessels operating as naval auxiliaries, providing mutual defence within the task grottp.

Peace, good order and security in the territorial sea is a matter for the coastal state as a consequence of its sovereignty over those waters. The presence of warships escorting civilian merchant vessels in the territorial sea, where it is without the consent of the coastal state, is not consistent with the right of innocent passage. Consistent with the extract from the Nicaragua Case quoted at the beginning of this chapter, it implies the use of force to protect the other vessels under escort and so is a threat of force to some extent.[3] Escort arguably is also an ‘activity not having a direct bearing on passage’. As discussed previously, given that the coastal state may temporarily close its territorial sea for security reasons, it seems unlikely that it would need to accept foreign warships escorting other vessels in its territorial sea.

Preventing non-innocentpassage in the territorial sea

This leads back to the question posed previously of what level of force a state could use to prevent non-innocent passage by a warship. Where a warship is conducting passage that does not meet the requirements of innocent passage, then the coastal state may require the warship to leave the territorial sea:

Article 30 Non-compliance by warships with the laws and regulations of the coastal State

If any warship does not comply with the laws and regulations of the coastal State concerning passage through the territorial sea and disregards any request for compliance therewith which is made to it, the coastal State may require it to leave the territorial sea immediately.

While the debate at the Third Conference indicates that the ‘sole recourse available’ is to require a warship to leave, this reflects that no further law enforcement action is possible other than pursuing the flag state as a matter of state responsibility. It is important at this point to distinguish between law enforcement and national self-defence. The text of the 1982 Convention is silent on this point. While the two concepts may be hard to distinguish m some circumstances, a warship breaching the requirements of innocent passage may still not actually pose a threat to the coastal state. For example, a warship that pollutes, or conducts fishing, would be acting contrary to article 19 but would not necessarily pose a serious threat to the coastal state that would justify a forceful response in national self-defence. Some other-violations of article 19, such as using weapons, would be more likely to create a perception of threat. It seems implicit in the words ‘require it to leave’ that the coastal state could take some measures as an exercise of its sovereignty. The use of force should be a last resort but, where the warship is clearly not complying with the request to leave, the coastal state should be able to resort to more practical measures to require the warship to leave.[4] It is consistent with article 3 of the Definition of Aggression that a state could take action against a warship in the territorial sea that was not acting within the requirements of innocent passage. Consistent also with the principles of necessity and proportionality, if the warship is not actually posing a lethal threat then the coastal state cannot use lethal force. Therefore, other measures might include placing obstructions in the water, such as booms or other vessels, to impede or direct passage. This may escalate to shouldering the warship. It could also even include warning shots amounting to a signal to the warship, noting the proactive measures listed in the Multinational Rules of Engagement Handbook discussed in Chapter 3. Should none of these methods compel the warship to leave, however, the sovereign immunity of the warship recognised under article 32 of the 1982 Convention means that the coastal state cannot board or apprehend it:

With such exceptions as are contained in subsection A and in articles 30 and 31, nothing in tins Convention affects the immunities of warships and other government ships operated for non-commercial purposes.

The International Tribunal for the Law of the Sea stated in the ARA Libertad case that:

Considering that a warship is an expression of the sovereignty of the State whose flag it flies ... in accordance with general international law, a warship enjoys immunity, including in internal waters.[5]

It would only be permissible to board a sovereign immune vessel in circumstances of aimed conflict or in national self-defence against an aimed attack involving the sovereign immune vessel. Preventing non-innocent passage to protect sovereignty is not the same as apprehension for the purpose of law enforcement. The options open to the coastal state are different and have a different character. This perhaps reinforces the point that the threshold for boarding, seizing or arresting sovereign immune vessels is veiy high. As stated in the ARA Libertad Case, this includes in internal waters.

  • [1] Lose art 5 2 Lose art 9 3 LOSCart 10 4 LOSCart 7 5 Ibid. 6 LOSC arts 47 and 48 7 LOSCart 49 8 LOSC art 52 9 LOSC art 38 10 LOSC art 53 11 See UN Treaties website, https://treaties.un.org’PagesA'iewDetailsIII.aspx?src=TREATY& mtdsg_no=XXI-6&chapter=21 &Temp=mtdsg3&clang=_en#EndDec 12 e.g. Declaration of the People’s Republic of China in respect of the United Nations Law of the Sea Convention, 25 August 2006, ibid. 13 See Myron Nordquist, Satya Nandan and Shabtai Rosenne (eds), United Nations Convention on the Law of the Sea: Commentary Online, ‘Innocent Passage in the Territorial Sea’, 151; Natalie Klein, Maritime Security and the Law of the Sea (Oxford University Press, 2011)38-39 14 Corfu Channel Case 30 15 For an argument that this is only a minority view, see Dale Stephens and Tim Quadno, ‘“Do as I Say and Not as I Do” Navigational Freedom and the Law of the Sea Convention’
  • [2] 2 IS Klein, n 14, 31-32; see Janies Kraska and Raul Pedrozo, International Maritime Security Law (Martinus Nijhoff Publishers, 2013) 256 on the Black Sea Bumping incident of 1988 where Soviet warships shouldered US warships to prevent them conducting innocent passage in the Soviet territorial sea. 3 LOSC arts 25 & 36
  • [3] Nicaragua Case 101 2 The commentary does not add much either, Nordquist et al. (eds), Commentary Online, n 14,255
  • [4] See Klein, n 14, 35-36; cf. Janies Kraska, ‘The Kerch Strait Incident: Law of the Sea or Law of Naval Warfare?’ EJIL Talk (online), 3 December 2018 www.ejiltalk.org/ the-kerch-strait-incident-law-of-the-sea-or-law-of-naval-warfare/ 2 See 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 https://ihl-databases.icrc.org/applic/ihl ihl.nsf/ Comment.xsp?action=openDocument&documentId=l A35EE65211Al 8AEC1258115004 4243A#78_B para 259: Even minor skirmishes between the armed forces, be they land, air or naval forces, would spark an international armed conflict and lead to the applicability of humanitarian law. Any unconsented-to military operations by one State in the territory of another State, including its national airspace and territorial sea, should be interpreted as an armed interference in the latter’s sphere of sovereignty and thus may be an international aimed conflict under Article 2(1). In the naval context, the innocent passage of foreign ships, including warships, in the territorial sea of another State is foreseen by the 1982 UN Convention on the Law of the Sea, in particular Articles 18-19. Such passage does not constitute an international armed conflict within the meaning of common Article 2.
  • [5] The ARA Libertad’ (Argentina v Ghana) ITLOS Case No 20, Provisional Measures, 15 December 2012,20-21, the Tribunal unanimously rejected the detention and attempted boarding of a sovereign immune Argentinian warship by Ghana, which was a result of the arrest of the ship following a private claim against the Argentine government brought in the Ghanaian High Court in Accra; see also, James Kraska reiterates the importance of sovereign immunity in ‘International Decisions: “The ARALibertad” (Argentina v Ghana)’ (2013) 107(2) American Journal of International Law 404,409-410 2 O’Connell had earlier stated that: it cannot be doubted that the principles of international law relating to sovereign immunity prohibit the arrest of both of these categories of ships [warships and other governmental ships operated for non-commercial purposes], in any circumstances short of declared war. in (edited by LA. Shearer) The International Law of the Sea; Volume II (Clarendon, Oxford, 1984) 965; Tom Ruys expresses a similar view, suggesting that it is a matter of international peace and security rather than law enforcement in ‘The Meanmg of “Force” and the Boundaries of the Jus Ad Bellum: Are “Minimal” Uses of Force Excluded from UN Charter Article 2(4)?’ 108(2) American Journal of International Law 159,186 3 ‘Self-defence and jurisdiction are not intrinsically related concepts’, O’Connell, ibid., at 964-965 4 LOSC art 8
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