1 Introduction
This chapter aims to sort out the issues of maritime boundary delimitation between China and Japan in the East China Sea in accordance with recent international case law on maritime boundary delimitation and to explore the possibilities of a solution which may be acceptable to both states. First, I would like to present a brief outline of the continental shelf delimitation dispute between China and Japan in the East China Sea, including each states’ claims on the maritime boundary delimitation. Then, I will deal with some important issues regarding those claims from the viewpoint of international law, in particular, of the case law on maritime boundary delimitation, and finally I would suggest some requirements to normalize the relationship between China and Japan in the East China Sea.
2 Claims to the Continental Shelf by the States Concerned in the East China Sea
2.1 Geographical and Geomorphological Features of the East China Sea
The East China Sea is a semi-enclosed sea, with an estimated area of 300,000 square kilometer, bounded by China and Taiwan Island to the west and south, the Korean Peninsula to the north and Japan’s Ryukyu islands to the east.1 The width of this body of water varies from 180 nautical miles at its narrowest
Thus, the East China Sea dispute on the continental shelf between China and Japan is related to the delimitation situation, in which two states are separated by less than 400 nautical miles of water. Furthermore, the geological and the geomorphological features of the seabed make it possible for one of two states to claim an entitlement to a continental shelf extending more than 200 nautical miles from the baseline of its own coast.
2.2 Maritime Claims to the Continental Shelf in East China Sea
2.2.1 China’s Claims
China has claimed that its sovereign right covers the shelf extending to the Okinawa Trough, based on the natural prolongation theory.5 In practice, China operates an offshore platform to exploit an oil and gas field in a full-fledged way at a Chinese-side point 45 kilometers from the median line. That is to say, China sees waters between the median line and the Okinawa Trough as subject to the bilateral dispute, and has demanded that the two states conduct joint development in waters east of the median line.6 China also seems to stick only
2.2.2 Japan’s Claims
Japan, in contrast, has rejected the applicability of the natural prolongation theory to the maritime delimitation in this area. Japan’s position is that under international maritime delimitation law, natural prolongation has no role to play in maritime boundary delimitation where the distance between the coasts of two opposite states is less than 400 nautical miles. Japan, instead, has asserted its claim to a continental shelf extending to a distance of 200 nautical miles from its coastal baseline. Therefore, Japan asserts that the median line between the two states should be the basis for delimiting the boundary, because the distance is less than 400 nautical miles between China and Japan in the East China Sea. Thus, Japan grounds its continental shelf claim on the distance criteria, provided in Article 76 (1) of the United Nations Convention on the Law of the Sea (unclos). To be specific, Japan’s position rests on the distance from the relevant coasts irrespective of any geological or geomorphological considerations.9
2.3
2.3.1 Disputed Sea Area
The first point is “Where is the disputed sea area between the two states?” China holds that the natural prolongation of the landmass extends to the edge of the Okinawa Trough,10 where China’s continental shelf comes to an end.11 On the other hand, Japan is of the view that the median line between the baseline of China’s coast and the ones of the Ryukyu Islands and other chains of islands that are spread from the mainland of Japan should be the boundary of the continental shelf in the East China Sea.12 Thus, these claims by the two states have brought the location of the disputed sea area to light. China argues that the disputed sea area stretches into the area west of the median line to Okinawa Trough. Against the Chinese argument, Japan claims that disputed sea area is all waters in the East China Sea wherever both states’ claims of 200 nautical miles overlap.13
2.3.2
The second point is the possibility of a single maritime boundary. The continental shelf is different from the eez by nature, because of the following facts: the continental shelf belongs to coastal states ipso facto and ab initio, and the legal title to the shelf does not depend on effective or normal occupancy, or explicit declaration; in contrast, explicit acts are required for establishing the eez. Therefore, unclos does not necessarily require any single boundary covering both the eez and the continental shelf, since the legal title to the eez is based on the standard distance of 200 nautical miles while the entitlement to the continental shelf depends upon the continuity or natural prolongation of the onshore geological structure.
But, in State Practice, states have tended to delimitate a common boundary for the eez and the continental shelf. Because the continental shelf extending up to 200 nautical miles from the coastline is covered by the eez, Japan’s position is that only any portion of the continental shelf beyond the eez boundary is related to the natural prolongation theory.
In the East China Sea, Japan has the eez delimitation as well as the continental shelf delimitation in mind while China adheres largely to the continental shelf delimitation.14 Drawing a single boundary for a continental shelf and an eez between China and Japan might support the Japan’s maritime delimitation arguments, because such a single boundary line would be drawn mainly on the basis of the distance criterion.
2.3.3 Applicable Maritime Delimitation Law
The main conflict on the maritime delimitation of the continental shelf between China and Japan is related to the contents of applicable legal principles and rules in delimiting continental shelves. China traditionally relies on the natural prolongation theory for the entitlement of its continental shelf,15 and claims equitable principle as the applicable law to the continental shelf
3 Recent Trends of Maritime Delimitation Rules in International Jurisprudence
3.1 Governing Provision of unclos with Regard to the Delimitation of the Continental Shelf
China and Japan are parties to unclos, which provides rules and principles for the delimitation of maritime boundaries. unclos has the provision on delimitation of the continental shelf in Article 83 (1), and Article 74 (1) of unclos, which regulates the delimitation of the eez, is almost the same as Article 83 (1). While these provisions do not refer to equidistance nor are related directly to the notion of equitable principles, they include the terms only “an equitable solution”,16 the meaning of which is not necessarily clear from their texts.17 Thus, the texts of these provisions alone cannot provide any definitive solution to the confrontation between the equidistance principle and the equitable principles for the criteria of the maritime delimitation of the continent shelf and eez.18 Therefore, the subsequent international jurisprudence on the maritime delimitation has complemented the contents of “an equitable solution” and contributed to clarify the delimitation method for it.
3.2
3.2.1 Predominance of the Equitable Principles/Relevant Circumstances Method in the International Court of Justice (icj) Early Cases on the Maritime Delimitation
In the early cases on the delimitation of the continental shelf, including the North Sea Continental Shelf cases,19 the Tunisia/Libya case,20 and the Libya/Malta case,21 the icj rejected the existence of any mandatory equidistance delimitation method of the continental shelf, which is provided by Article 6 of the 1958 Convention on the Continental Shelf, and has followed the equitable principles/relevant circumstances method. Particularly in the Gulf of Maine case, the Chamber of the icj took a more discretionary approach, referring to the set of fundamental rules.22 Its formulation is the most result-oriented one, therefore, “it eliminated almost any rule-orientation and turned delimitation into a fully discretionary operation”.23
3.2.2
As the Chamber pointed out properly in the Gulf of Maine case, however, “[T]here has been no systematic definition of the equitable criteria that may be taken into consideration for an international maritime delimitation, and this would in any event be difficult a priori, because of their highly variable adaptability to different concrete situations” .24 Thus, this concern may induce the international courts and tribunals to look for more objectively determined delimitation methods and criteria, as opposed to subjective equity consideration.
In fact, the icj confirmed in the Jan Mayen case, that “[P]rima facie, a median line delimitation between opposite coasts results in general in an equitable solution, particularly if the coasts in question are nearly parallel”.25 Most of the subsequent international jurisprudence on maritime delimitation, including the Qatar v. Bahrain case,26 the Cameroon v. Nigeria case,27 the Eritrea/Yemen Arbitration,28 the Barbados/Trinidad and Tobago Arbitration,29 the Guyana/Surinam Arbitration,30 and the Nicaragua v. Honduras case,31 all reaffirmed that a provisional equidistance or median line should be drawn first
Finally, in the Black Sea Maritime Delimitation case,32 the Court, following the previous judgments on the object of maritime delimitation,33 articulated so-called three-stage approach on the delimitation process: first, the decision-maker draws a provisional equidistance line, and second, it considers whether there are factors for adjustment or shifting of that line to achieve an equitable result, and third, it conducts an ex-post facto disproportionality test to verify that the adjusted equidistance line does not lead to an inequitable result by reason of any marked disproportion between the ratio of the respective coastal lengths and the ratio between the relevant maritime area of each State.34 Most of the subsequent maritime delimitation cases, for example, the Bay of Bengal cases,35 the Nicaragua v. Colombia case,36 the Peru v. Chile case,37 the Ghana/Côte d’Ivoire case,38 and the Costa Rica v. Nicaragua case39 follow this three-stage approach in the delimitation of the eez and the continental shelf. Therefore, international jurisprudence on maritime delimitation indicates
3.3 Rejecting Natural Prolongation as a Relevant Factor in Delimitation of Continental Shelf within 200 Nautical Miles
On the other hand, the natural prolongation theory, which China adopts for maritime delimitation, as a criterion of delimitation of continental shelf within 200 nautical miles has been rejected by the recent international jurisprudence.
It is in the North Sea Continental Shelf cases40 that the icj first referred to the natural prolongation as a criterion of boundary delimitation of the continental shelf. In the Tunisia/Libya case,41 the Court rejected geological and geomorphological circumstances for considering the delimitation of the boundary, but in fact, it reserved the possibility of their consideration in future cases.42 Thus, later, in the Gulf of Maine case,43 the Chamber of the Court observed the applicability of geological circumstances in delimiting a single boundary of the continental shelf and the eez within 200 nautical miles in the Gulf of Maine area. It is on these judgments that China’s legal contention is based in the maritime delimitation in the East China Sea where according to China, the Okinawa Trough presents the natural break between the Chinese and the Japanese continental shelves.
In the Libya/Malta case,44 however, the Court refused the parties’ arguments based on geology and geomorphology, and rejected natural prolongation as a relevant factor in so far as the continental shelf within 200 nautical miles was concerned.45 Moreover, in the Nicaragua v. Colombia case, the Court also rejected Nicaragua’s contention based upon natural prolongation, and
4 Diving or Digging into the Search for a Tolerable Panacea in the East China Sea?
4.1 Possible Results of the Application of the Current Legal Rules to the Delimitation of the Continental Shelf between China and Japan in the East China Sea
4.1.1 Application of the Three-Stage Approach to the Continental Shelf Delimitation between China and Japan
International case law supports the thesis that the three-stage approach dominates in recent international jurisprudence. According to this method, first, the provisional equidistance/median line should be drawn between the relevant coastlines of China and the ones of Japan. This way seems to favor Japan’s position on the continental shelf delimitation, because Japan has consistently argued the median line as the continental shelf boundary between China and Japan in the East China Sea. Thus, apparently the case law on the maritime delimitation may provide some advantages with the Japanese side. But this median line is still provisional, and it could be adjusted if there are any relevant factors for the equitable results. Usually, the equidistance/median line may give both coastal States the equitable results, but there is no principle without exception.
4.1.2 Existence of the Relevant Factors Which Could Adjust the Provisional Median Line for the Equitable Result
As for the relevant circumstances, most noteworthy here is coastal length disparity, which could by itself determine the adjustment of an equidistant/median line. The case law on the maritime delimitation acknowledges that “a substantial difference in the lengths of the parties’ respective coastlines may be a factor to be taken into consideration in order to adjust or shift the
In the Nicaragua v. Colombia case, the icj observed that “it is normally only where the disparities in the lengths of the relevant coasts are substantial that an adjustment or shifting of the provisional line is called for”.56 The Court then found that the result achieved by the application of the provisional line in a ratio of 8.2:1 coastal length in Nicaragua’s favour “does not entail such a disproportionality as to create an inequitable result”.57 In the case of the East China Sea, even if the geographical features seem to show approximately a ratio of 2:1 coastal length in China’s favor,58 which is dependent upon how to specify where is the respective relevant coasts of the two states, in my view, it is not very convincing that this ratio should be decisive for the provision of the median line to be adjusted in China’s favor, compared with other similar cases.59
The existence of islands can be also one of the relevant circumstances for the equitable results. Islands may give some impact on the maritime delimitation under the condition that it belongs decisively to one of the parties to the dispute. In the East China Sea, China argues that the Senkaku/Diaoyu Islands
As for the Senkaku/Diaoyu Islands, apart from the questions of the existence or non-existence of dispute and the holder of territorial sovereignty over it, whether or not they should satisfy the objective pre-conditions set forth in Article 121 (3) of unclos, especially in light of the requirements which the South China Sea Arbitration Award clarified,60 remains to be seen. However, it can be safely said that, whether or not they qualify as fully entitled islands, their potential effects on the future maritime boundary delimitation in the East China Sea is likely to be very limited.61 In fact, the Senkaku/Diaoyu Islands need not to be considered as relevant circumstances for the adjustment of the provisional median line.62
4.1.3 Possibility of Separate (but Partially Overlapping) Maritime Boundaries?
Many cases concerning single maritime boundaries can be seen in international jurisprudence,63 but in State Practice, there are only a few cases in which the parties concerned agreed to create two separate maritime boundaries.64
At first glance, this example might be used to support China’s legal reasoning in relation to Japan’s position. Nevertheless, the 1997 Australia / Indonesia Treaty can be argued to be inconsistent with unclos, because the eez not only contains rights in the water column but it also covers continental shelf rights in the seabed and subsoil. Under the relevant provisions of unclos, the eez is difficult to be considered exclusively to concern activities on the water column, in separation from the seabed.66 It is natural, from the practical viewpoint as well as the legal one, that the states concerned should seek a single boundary line in the maritime delimitation.
Finally, the 1997 Treaty, though signed, has not entered into force. The main reason is that Indonesia withdrew from East Timor in October 1999. Later on, in 2018, Timor-Leste sought to negotiate a permanent eez and continental shelf boundary with Australia, on the basis of equidistance line. Both states concluded a comprehensive treaty setting maritime boundaries between the two states in the Timor Sea, with the assistance of a Conciliation Commission. As this example shows, the possibility that separate and partially overlapping continental shelf and eez boundaries may overcome debate over the role of geographical factors in maritime boundary delimitation should not be denied. However, considering that the 1997 Treaty was never ratified, the value as a precedent of the Treaty is very limited for the East China Sea dispute.67
4.2 Towards Strengthening a Joint Development Framework between China and Japan
4.2.1 “Rediscovery” of the 2008 Agreement
China and Japan have already shared a common position as a restarting point for win-win solution. Since 2004, China and Japan negotiated to proceed for
From the view of managing any conflict between China and Japan in the East China Sea, in particular on the resources under that sea area, the 2008 Agreement should and could be an important starting point, because the
4.2.2 Conditions for the Revival of the June 2008 Agreement
Regrettably, the cooperative atmosphere created by this Agreement between two states has been wrecked,72 in particular after the recurrence of the Senkaku/Diaoyu Islands sovereignty problem in 2012. Nevertheless, China and Japan have the obligation to make every effort not to jeopardize or hamper the reaching of the final agreement under Article 83 (3) of unclos, which requires them to refrain from engaging in unilateral action that may aggravate a dispute.73 In reality, there is no choice but to shelve this problem for a while, whether the perception that there is a territorial dispute between two states should be recognized or not. The 2008 agreement should be re-estimated as a starting point for next stage, so that China and Japan may rebuild trust in each other in the East China Sea.
The restart of the joint development between two states requires cooperation which implies that there should be prevailing feelings of goodwill and friendliness between them. It is true that the joint development agreement should facilitate coordinated and systematic operations in the disputed sea area, but ultimately, it is very important for the parties to demonstrate the required level of political goodwill in support of this cooperative solution.
In December 2018, when China deployed a jack-up drilling rig near the provisional median line between China and Japan in the East China Sea, Japan protested against China, considering that drilling operations so close to the provisional median line entailed the risk of tapping the petroleum reserve straddling the maritime areas of the two states. Unfortunately, an unsettled atmosphere still prevails between China and Japan in developing their indigenous seabed energy resources in the East China Sea. Access to such valuable
That is why China and Japan tried to rebuild confidence with the respective political will to implement the 2008 agreement effectively. To increase the friendly relationship between the two states, at first, Japan should cooperate with China in implementing the petroleum operations in the area near the median line, while China should respect the significance of the median line in this maritime sea area, even if it does not officially recognize the median line.
5 Conclusions
First, the continental shelf between China and Japan in the East China Sea should be delimited in accordance with the case law on maritime delimitation, that is, the “three-stage approach”, just in case both states would agree to the conclusion of a maritime boundary treaty. Second, in reality, however, the current situation is becoming so intense that it is now difficult to negotiate any work of maritime delimitation between them. Third, China and Japan should do their best to gain the confidence from its counterpart in order to reactivate joint development operations in the East China Sea. The 2008 Agreement might be a starting point for their cooperation.
To build confidence each in other, China and Japan should take into consideration the following: First, they should refrain from conducting any measure which might deteriorate their relationship, including any such activities with regards to the Senkaku/Diaoyu problem. Second, while China should avoid drilling unilaterally in the area across the median line between the two states, Japan should consider the possibility of increasing the joint development operation within its 200 nautical miles area from its coast.
I hope and deeply believe that only such strong efforts to build mutual confidence by the two states must turn the East China Sea into a “Sea of Peace, Cooperation and Friendship” in the near future.
The overview of the East China Sea, see, U.S. Energy Information Administration, “East China Sea”. Available at
Thomas J. Schoenbaum, “Finding Solutions to the Disputes between China and Japan”, in idem (ed.), Peace in Northeast Asia. Resolving Japan’s Territorial and Maritime Disputes with China, Korea and the Russian Federation (Edward Elgar, 2008), p. 91.
Jianjun Gao, “The Okinawa Trough Issue in the Continental Shelf Delimitation Dispute within the East China Sea”, Chinese Journal of International Law, Vol.9 (2010), p. 145.
Constantinos Yiallourides, Maritime Disputes and International Law. Disputed Waters and Seabed Resources in Asia and Europe (Routledge, 2019), p. 94.
Haiwen Zhang, “Legal Issues concerning the East China Sea Delimitation – A Chinese Perspective on the Sino-Japanese the East China Sea Dispute – ”, Japanese Yearbook of International Law, Vol.51 (2008), pp. 125–126. For China’s legal position on the continental shelf in general, see, Working Paper submitted by the Chinese Delegation: Sea Area within the Limits of National Jurisdiction, UN Doc.A/ac.138/sc.ii/L.34, Report of the Committee on the Peaceful Uses of the Sea-Bed and the Ocean Floor beyond the Limits of National Jurisdiction, Volume iii, gaor, 28th Session, Supplement No.21 (A/9021), p. 74.
It is reported, nevertheless, that in its efforts to develop the offshore oil since 1980, China has limited its exploration and exploitation mainly to its side of the Chinese-Japanese equidistance line in consideration of the lack of agreement achieved between the two states. See, Junwu Pan, “Way Out: The Possibility of a Third-Party Settlement for the Sino-Japanese Maritime Boundary Dispute in the East China Sea”, China: An International Journal, Vol.6 (2008), p. 193.
However, the Chinese Government may accept a single maritime boundary if China’s claim that its eez prolongs naturally to the Okinawa Trough should be upheld. The Ministry of Foreign Affairs of the People’s Republic of China, “China’s Oil and Gas Development in the East China Sea is Justified and Legitimate”, July 27, 2015. Available at <
The delimitation of eez in the East China Sea (a principle based on distance) could produce a more disadvantageous result for China than the delimitation of continental shelf (a principle based on natural prolongation). See, H. Schulte Nordholt, “Delimitation of the Continental Shelf in the East China Sea”, Netherlands International Law Review, Vol.32 (1985), p. 134. For the China’s position, see, Ji Guoxing, “Sino-Japanese Jurisdictional Delimitation in East China Sea: Approaches to Dispute Settlement”, in Seoung-Yong Hong & Jon M. Van Dyke (eds.), Maritime Boundary Disputes, Settlement Processes, and the Law of the Sea (Brill, 2009), pp. 82–84.
Ministry of Foreign Affairs of Japan, “Japan’s legal position on the development of natural resources in the East China Sea”. Available at <
Goldie compared the Norwegian Trough, which the icj took as an example of natural prolongation in the North Sea Continental Shelf cases, with the Okinawa Trough, and suggested that the latter divides the seabed of the East China Sea into two major provinces and thus provides a clear boundary in terms of the icj’s formula of natural prolongation. See, L.F.E. Goldie, “The International Court of Justice’s ‘Natural Prolongation’ and the Continental Shelf Problem of Islands”, Netherlands Yearbook of International Law, Vol.4 (1973), pp. 252–254.
In Chapter “5. Natural Prolongation of Land Territory” in the Executive Summary of the Submission by China to the Commission on the Limits of the Continental Shelf (clcs) on 14 December 2012, it stated the following: the East China Sea (ecs) “consists of three geomorphologic units: the shelf, the slope and the Okinawa Trough”, which is “the natural termination of the continental shelf of ecs”. Submission by the People’s Republic of China Concerning the Outer Limits of the Continental shelf beyond 200 Nautical Miles in Part of the east China Sea, Executive Summary, pp. 3–5. <
Ministry of Foreign Affairs of Japan, “Japan’s Legal Position on the Development of Natural Resources in the East China Sea”, August 6, 2015, Available at <
In this case, the question where the disputed area is situated may be related to the relationship between distance and natural prolongation in the continental shelf delimitation. If distance criterion prevails over natural prolongation, the Japan’s 200 nautical miles continental shelf cannot be encroached by the China’s beyond 200 nautical miles continental shelf. On this subject, see, Xuexia Liao, “Is There a Hierarchical Relationship between National Prolongation and Distance in the Continental Shelf Delimitation?” The International Journal of Marine and Coastal Law, Vol.33 (2018), pp. 79–115. From the Chinese perspective, “if the natural prolongation of one state’s land territory exceeds 200 nautical miles from its coast, but the other state’s does not, then the “area of overlapping entitlements” will be the area bounded by the limits of the natural prolongation of the former state’s land territory on the one hand, which is therefore different from the “area of overlapping entitlements” in the case of eez delimitation. See, Gao Jianjun, “Joint Development in the East China Sea: Not an Easier Challenge than Delimitation”, The International Journal of Marine and Coastal Law, Vol.23 (2008), pp. 44–45.
It does not exclude any possibility that China will agree to median line as the delimitation line of the eez with Japan, though China still insists on natural prolongation for delimitation of the continental shelf. In that case, there would be two different delimitation lines in the East China Sea, thus definitely bringing difficulties of law enforcement and exercise of jurisdiction for both states. Zou Keyuan, “China’s Exclusive Economic Zone and Continental Shelf: Development, Problems, and Prospects”, Marine Policy, Vol.25 (2001), pp. 77–78.
Zhiguo Gao, “China and the LOS Convention”, Marine Policy, Vol.15 (1991), p. 205.
Thus, under Article 74 (1) and Article 83 (1) no predominance is given either to equitable principles or to equidistance. See, Satya N. Nandan & Shabtai Rosenne (eds.), United Nations Convention on the Law of the Sea 1982. A Commentary, Volume ii (Martinus Nijhoff Publishers, 1993), pp. 814, 913. That means a compromise between these two approaches resulted from a common perspective: the need to avoid inequitable solutions. See, Nuno Marqus Antunes, Towards the Conceptualisation of Maritime Delimitation. Legal and Technical Aspects of a Political Process (Brill, 2003), pp. 88–89.
Article 74 (1) as well as Article 83 (1) “offers scant explanation about the content of ‘an equitable solution’. Thus, the equitableness of maritime boundaries must be evaluated on a case-by-case basis”. Yoshifumi Tanaka, “Article 83”, in Alexander Proeless (ed.), United Nations Convention on the Law of the Sea. A Commentary (c.h. Beck, 2017), p. 658.
For the confrontation between the equidistance principle and the equitable principles, Malcolm D. Evans, “Maritime Boundary delimitation”, in Donald R. Rothwell, Alex G. Oude Elferink, Karen N. Scott & Tim Stephens (eds.), The Oxford Handbook of the Law of the Sea (o.u.p., 2015), pp. 256–259.
North Sea Continental Shelf, Judgment, i.c.j. Reports 1969, pp. 46–47, para. 82. On the other hand, in the UK/France Continental Shelf Arbitration, the Court of Arbitration integrated the equidistance-special circumstances rule in the whole body of the rules of law that were to result in delimitation in accordance with equitable principles and observed that a median line would “normally effect a broadly equitable delimitation” in the case of opposite states. Case concerning the Delimitation of the Continental Shelf between the United Kingdom of Great Britain and Northern Ireland, and the French Republic, Decision of 30 June 1977, r.i.a.a., Vol. xviii, pp. 47–48, para. 75, p. 56, para. 95.
Continental Shelf (Tunisia / Libyan Arab Jamahiriya), Judgment, i.c.j. Reports 1982, p. 59, para. 70.
Continental Shelf (Libyan Arab Jamahiriya / Malta), Judgment, i.c.j. Reports 1985, pp. 37–38, para. 43. In this case, however, the Court observed that in the delimitation between states with opposite coasts, “the tracing of a median line between those coasts, by way of a provisional step in a process to be continued by other operations, is the most judicious manner of proceeding with a view to the eventual achievement of an equitable result”. Ibid., p. 47, para. 62. See also, Yoshifumi Tanaka, Predictability and Flexibility in the Law of Maritime Delimitation, 2nd Edition (Hart Publishing, 2019), pp. 71–72.
Delimitation of the Maritime Boundary in the Gulf of Maine Area, Judgment, i.c.j. Reports 1984, pp. 299–300, para. 112.
Thomas Cottier, Equitable Principles of Maritime Boundary Delimitation. The Quest for Distributive Justice in International Law (Cambridge U.P., 2015), p. 407. In the Guinea/Guinea-Bissau case, the Arbitral Tribunal also restated the wide-open, discretionary approach, as the Chamber took in the Gulf of Maine case. Affaire de la délimitation de la frontière maritime entre la Guinée et la Guinée-Bissau, sentence du 14 février 1985, r.i.a.a., Vol. xix, pp. 181–182, para. 88.
i.c.j. Reports 1984, p. 312, para. 157.
Maritime Delimitation in the Area between Greenland and Jan Mayen, Judgment, i.c.j. Reports 1993, p. 66, para. 64.
Maritime Delimitation and Territorial Questions between Qatar and Bahrain, Merits, Judgment, i.c.j. Reports 2001, p. 111, paras. 228–230.
Land and Maritime Boundary between Cameroon and Nigeria (Cameroon v. Nigeria: Equatorial Guinea intervening), Judgment, i.c.j. Reports 2002, pp. 441–442, paras. 288–290.
Award of the Arbitral Tribunal in the Second Stage of the Proceedings between Eritrea and Yemen (Maritime Delimitation), Decision of 17 December 1999, r.i.a.a., Vol. xxii, p. 365, paras. 131-132.
Award of the Arbitral Tribunal concerning the Maritime Boundary between Barbados and the Republic of Trinidad and Tobago, Decision of 11 April 2006, r.i.a.a., Vol. xxvii, pp. 214–215, para. 242.
Award in the Arbitration regarding the Delimitation of the Maritime Boundary between Guyana and Suriname, Award of 17 September 2007, r.i.a.a., Vol. xxx, p. 95, para. 342.
Territorial and Maritime Dispute between Nicaragua and Honduras in the Caribbean Sea (Nicaragua v. Honduras), Judgment, i.c.j. Reports 2007, p. 745, para. 281. The Court, however, adopted, instead of the equidistance principle, the bisector method, according to which some form of bisector of the angle created by lines representing the relevant mainland coasts could be a basis for the delimitation, though confirming that equidistance remains the general rule. Ibid., p. 746, para. 287.
Maritime Delimitation in the Black Sea (Romania v. Ukraine), Judgment, i.c.j. Reports 2009, pp. 101–103, paras. 115–122.
“The purpose of delimitation is not to apportion equal shares of the area, nor indeed proportional shares”. “The object of delimitation is to achieve a delimitation that is equitable, not an equal apportionment of maritime area”. Ibid., pp. 99–100, paras. 110–111. The court observed that this means that “[E]quity does not necessarily imply equality”. i.c.j. Reports 1969, p. 50, para. 91. See also, Davor Vidas, “Consolidation or Deviation? On Trends and Challenges in the Settlement of Maritime Delimitation Disputes by International Courts and Tribunals”, in Nerina Boschiero, Tullio Scovazzi, Cesare Pitea & Chiara Ragni (eds.), International Courts and the Development of International Law. Essays in Honour of Tullio Treves (Springer, 2013), p. 328.
See also, Mathias Forteau et Jean-Marc Thouvenin (dir.), Traite de Droit International de la Mer (Pedone, 2017), pp. 600–607 [Alain Pellet].
Delimitation of the Maritime Boundary in the Bay of Bengal (Bangladesh / Myanmar), Judgment, itlos Reports 2012, pp. 67–68, paras. 238–240; The Bay of Bengal Maritime Boundary Arbitration between the People’s Republic of Bangladesh and the Republic of India, Award of 7 July 2014, r.i.a.a., Vol. xxxii, pp. 104–106, paras. 337–346.
Territorial and Maritime Dispute (Nicaragua v. Colombia), Judgment, i.c.j. Reports 2012, pp. 695–698, paras. 190–199.
In this case, the Court said that “[I]n the first, it constructs a provisional equidistance line unless there are compelling reasons preventing that”. Maritime Dispute (Peru v. Chile), Judgment, i.c.j. Reports 2014, p. 66, para. 180.
Delimitation of the Maritime Boundary in the Atlantic Ocean (Ghana / Côte d’Ivoire), Judgment, itlos Reports 2017, p. 103, para. 360.
Maritime Delimitation in the Caribbean Sea and the Pacific Ocean (Costa Rica v. Nicaragua) and Land Boundary in the Northern Part of Isla Portillos (Costa Rica v. Nicaragua), Judgment, i.c.j. Reports 2018, p. 190, para. 135.
i.c.j. Reports 1969, p. 32, para. 43, p. 54, para. 101 (C) (1).
i.c.j. Reports 1982, p. 57, para. 66.
Yiallourides, supra note 4, p. 113.
i.c.j. Reports 1984, p. 327, paras. 194–195.
i.c.j. Reports 1985, pp. 35–36, paras. 39–40.
To the contrary, some authors argue that the Court left open the possibility that the geological features on the seabed might be relevant to delimitation of the continental shelf beyond 200 nautical miles from the baselines. David A. Colson, “The Delimitation of the Outer Continental Shelf between Neighbouring States”, American Journal of International Law, Vol.97 (2003), pp. 102–103; Øystein Jensen, “Maritime Boundary Delimitation beyond 200 Nautical Miles: The International Judiciary and the Commission on the Limits of the Continental Shelf”, Nordic Journal of International Law, Vol.80 (2015), pp. 599–600; Bjarni Már Magnússon, The Continental Shelf Beyond 200 Nautical Miles (Brill, 2015), p. 17.
i.c.j. Reports 2012, p. 703, para. 214.
“In the view of the Tribunal, the delimitation method to be employed in the present case for the continental shelf beyond 200 nautical miles should not differ from that within 200 nm”. itlos Reports 2012, p. 117, para. 455. See also, r.i.a.a., Vol.xxxii, p. 138, paras. 457–458.
Tanaka, supra note 21, p. 295.
All of the tribunals in the Bay of Bengal cases and the Ghana/Côte d’Ivoire case decided to use the “equidistance/relevant circumstances method in the delimitation of the outer continental shelf. Jianjun Gao, “The Delimitation Method for the Continental Shelf Beyond 200 Nautical Miles: A Reflection on the Judicial and Arbitral Decisions”, Ocean Development & International Law, Vol.51 (2020), p. 124. Davenport acknowledges that “[A]fter the Bangladesh/Myanmar Case, it may be difficult for China to continue to argue that natural prolongation is still a valid basis of entitlement under international law”, though not denying the possibility that China is entitled to an extended continental shelf in area less than 400 nautical miles. Tara Davenport, “The China-Japan Dispute over Entitlement in the East China Sea: Legal Issues and Prospects for Resolution”, in Clive Schofield, Seokwoo Lee & Moon-Sang Kwon (eds.), The Limits of Maritime Jurisdiction (Brill, 2014), p. 308.
Paik said that “the concept of natural prolongation was destined to be involved with the question of the outer limits and its consequent impact on delimitation” (Jin-Hyun Paik, “The Origin of the Principle of Natural Prolongation: North Sea Continental Shelf Cases Revisited”, in Lilian del Castillo (ed.), Law of the Sea, From Grotius to the International Tribunal for the Law of the Sea. Liber Amicorum Judge Hugo Caminos (Brill, 2015), p. 589.), but the questions of entitlement of continental shelf and of its delimitation, even if they are complementary, should be clearly distinct. i.c.j. Reports 1985, p. 30, para. 27.
Nuno Marques Antunes & Vasco Becker-Weinberg, “Entitlement to Maritime Zones and Their Delimitation. In the Doldrums of Uncertainty and Unpredictability”, in Alex G. Oude Elferink, Tore Henriksen & Signe Veierud Busch (eds.), Maritime Boundary Delimitation: The Case Law (Cambridge U.P., 2018), p. 67.
Hyun Jung Kim, “Natural Prolongation: A Living Myth in the Regime of the Continental Shelf?” Ocean Development & International Law, Vol.45 (2014), p. 382.
It is asserted that by the mid-1990s international jurisprudence on maritime delimitation has indicated the contemporary trend to disregard geological features, which means that the Okinawa Trough is unlikely to affect the maritime boundary delimitation. See, Jonathan I. Charney, “Central East Asian Maritime Boundaries and the Law of the Sea”, American Journal of International Law, Vol.89 (1995), p. 740.
i.c.j. Reports 2002, p. 446, para. 301.
It is to be noted that coastal length disparity, which is related to a relevant circumstance at the second stage, and disproportionality, which leads the Court to assess the ratio between the marine areas allocated to each state at the third stage, have distinct functions in the three-stage approach. Massimo Lando, Maritime Delimitation as a Judicial Process (Cambridge U.P., 2019), p. 281.
i.c.j. Reports 2012, p. 702, para. 210. The Court also observed in the Black Sea Maritime Delimitation case that “[W]here disparities in the lengths of coasts are particularly marked, the Court may choose to treat that fact of geography as a relevant circumstance that would require some adjustments to the provisional equidistance line to be made”. i.c.j. Reports 2009, p. 116, para. 164.
i.c.j. Reports 2012, p. 717, para. 247.
“[T]he proportionality between the lengths of the coastal states’ respective coastlines in the South Region would result in a delimitation of the continental shelf in a ratio of approximately 64 to 36 in favor of China”, when the East China Sea would be divided into North and South regions along 30°N. See, Wei-chin Lee, “Troubles under the Water: Sino-Japanese Conflict of Sovereignty on the Continental Shelf in the East China Sea”, Ocean Development & International Law, Vol.18 (1987), p. 599.
In the Jan Mayen case, the Court observed that the ratio of relevant coasts was approximately 1:9 in Denmark’s favour (i.c.j. Reports 1993, p. 65, para. 61.), but even in this case, it did not consider a ratio of approximately 1:2.7 relevant area in Denmark’s favour to be significantly disproportionate. See, i.c.j. Reports 2012, p. 717, para. 246.
The South China Sea Arbitration between the Republic of the Philippines and the People’s Republic of China, Award of 12 July 2016, r.i.a.a., xxxiii, pp. 387–390, paras. 539–551.
Yiallourides, supra note 4, pp. 137–138.
The legal status of the Senkaku/Diaoyu Islands would give little influence upon the maritime boundary delimitation, because it is possible to separate the issue of maritime boundary delimitation from that of ownership of the Senkaku/Diaoyu Islands, given the recent development of international jurisprudence ignoring small islets in seabed boundary delimitations between opposite states. Suk-Kyoon Kim, “Perspectives on East China Sea Maritime Disputes: Issues and Context”, in Schofield, Lee & Kwon (eds.), supra note 49, p. 291.
“The Court observes that the concept of a single maritime boundary does not stem from multilateral treaty law but from State practice”. i.c.j. Reports 2001, p. 93, para. 173. For the state practice and international jurisprudence of a single maritime boundary line, see, Laurent Lucchini, “Plaidoyer pour une ligne unique de délimitation”, in Rafael Casado Raigón et Giuseppe Cataldi (dir.), L’évolution et l’état actuel du droit international de la mer. Mélanges de droit de la mer offerts à Daniel Vignes (Bruylant, 2009), pp. 564–570.
The regimes of the eez and the continental shelf “are separate, but to avoid the difficult practical problems that could arise were one Party to have rights over the water column and the other rights over the seabed and subsoil below that water column, a single maritime boundary can be drawn”. r.i.a.a., Vol. xxx, pp. 92–93, para. 334.
For the text of the 1997 Treaty establishing an eez Boundary and Certain Seabed Boundaries and the commentary on it, see, Jonathan I. Charney & Robert W. Smith (eds.), International Maritime Boundaries, Vol. iv (Brill, 2002), pp. 2697–2727.
Max Herriman & Marti Tsamenyi, “The 1997 Australia – Indonesia Maritime Boundary Treaty: A Secure Legal Regime for Offshore Resource Development?” Ocean Development & International Law, Vol.29 (1998), pp. 364–365.
Yiallourides, supra note 4, pp. 120–124.
Reinhard Drifte, “The East China Sea. Sea of Regional and Global Confrontation”, in Gordon Houlden & Nong Hong (eds.), Maritime Order and the Law in East Asia (Routledge, 2018), p. 41; Chung-min Tsai, “Sino-Japanese Relations Over the East China Sea: The Case of Oil and Gas Fields”, Journal of Territorial and Maritime Studies, Vol.3 (2016), pp. 74–76.
Ministry of Foreign Affairs of Japan, “The Current Status of China’s Unilateral Development of Natural Resources in the East China Sea”. Available at <
The conclusion of this Agreement is in line with the spirit and provisions of unclos which encourages States concerned to work out provisional arrangements including joint development agreement pending the settlement of their maritime boundary disputes. Keyuan Zou, “Maritime Conflict and Cooperation in East Asia. Recent Developments and Future Prospects”, in Barthélémy Courmont, Frédéric Lasserre & Éric Mottet (eds.), Assessing Maritime Disputes in East Asia. Political and Legal Perspectives (Routledge, 2017), p. 41.
Shigeki Sakamoto, “Japan-China Dispute over Maritime Boundary Delimitation – From a Japanese Perspective – ”, Japanese Yearbook of International Law, Vol.51 (2008), p. 118.
Taisaku Ikeshima, “Recent Developments in Maritime Delimitation: Any Implication for Territorial and Maritime Boundary Disputes in East Asia?” Graduate School of International Culture and Communication Studies, Vol.4 (2017), p. 83. The two states failed to conclude a provisional arrangement of a practical nature on some kind of cooperation on hydrocarbon exploitation. Zhang Xinjun, “Why the 2008 Sino-Japanese Consensus on the East China Sea Has Stalled: Good Faith and Reciprocity Considerations in Interim Measures Pending a Maritime Boundary Delimitation”, Ocean Development & International Law, Vol.42 (2010), p. 61.
Sean D. Murphy, “Obligations of States in Disputed Areas of the Continental Shelf”, in Tomas Heidar (ed.), New Knowledge and Changing Circumstances in the Law of the Sea (Brill, 2020), pp. 198–200.