1. Textual approach

It is well established that the principles underlying Articles 31 to 33 of the Vienna Convention reflect customary international law.Footnote ¹⁶ While the Vienna Convention includes three articles that deal with treaty interpretation rules, it should be noted that Article 31 of the Vienna Convention provides a single, albeit general, rule of treaty interpretation,Footnote ¹⁷ consistent with which “[a] treaty shall be interpreted in good faith in accordance with the ordinary meaning to be given to the terms of the treaty in their context and in light of its object and purpose”.Footnote ¹⁸ Accordingly, the single rule includes four elements, all of which “are to be applied together, not individually”.Footnote ¹⁹ It is commonly accepted that an “[i]nterpretation must be based above all upon the text of the treaty”.Footnote ²⁰ Thus, it has been asserted that “the first duty of a tribunal which is called upon to interpret and apply the provisions of a treaty is to endeavor to give effect to them in their natural and ordinary meaning in the context in which they occur”.Footnote ²¹

It follows that customary treaty interpretative rules dictate that Article 76(6) should primarily be construed according to a textual approach.Footnote ²²

The composite elements of the continental margin are spelt out in paragraph 3 of Article 76. It is composed of two sentences, the first being a positive definition, while the second is a negative definition:

It follows from paragraph 3 that three elements constitute the continental margin: (i) the shelf, (ii) the slope, and (iii) the rise, while the deep ocean floor with its oceanic ridges is excluded from the continental margin. There is no doubt that this definition is arbitrary in contrast to the meaning and scope of the notion continental margin under the natural sciences.Footnote ²⁴ This arises in a particularly lucid manner if reference is made to paragraph 4(a) of Article 76, which sets forward the rules determining the outer edge of the continental margin:

The above formulae are alternatives. In both situations, the foot of the continental slope can be seen as a generative feature insofar as it concerns the determination of the outer edge of the continental margin, an assertion which appears amply in the Scientific & Technical Guidelines of the Commission on the Limits of the Continental Shelf [S&TG].Footnote ²⁶ There are no preconditions for applying the formulae in paragraph 4(a)(i)–(ii) other than determining the foot of the continental slope. Thus, the rise under paragraph 3 of Article 76 may cover areas of sea bed on which there are no sediments, for example, or may be located on a crustal structure alien to that of the land mass from which the sea floor high is the submerged prolongation. From a scientific perspective, such areas of the sea bed would not be considered constitutive of the continental margin, but rather the deep ocean floor.Footnote ²⁷ However, such areas of sea bed are part of the continental margin for the purposes of applying Article 76 of UNCLOS. This is the consequence of the mere fact that the general rule of treaty interpretation does not support an assertion that the continental margin is contingent upon the land mass having a geological affinity with a particular crustal structure of the relevant seafloor high that supposedly generates the outer limits of the continental shelf. This is in particular reflected in Article 76(4)(a)(i)–(ii), which determines the seaward extent of the rise, but which operation is governed by the umbrella provision in paragraph 4(b) of Article 76. It is apparent that the precise point of departure from which the seaward extent of the rise is determined is contingent upon the identification of the base of the continental slope: “In the absence of evidence to the contrary, the foot of the continental slope shall be determined as the point of maximum change in the gradient at its base.”Footnote ²⁸

Paragraph 4(b) of Article 76 is critical to the proper understanding of the second sentence of paragraph 3, as it provides the rule which determines the approximate location in which the foot of the continental slope is located. Thus, any part of the seafloor which falls landward of that particular location is appropriately slope or shelf for the purpose of paragraph 3 of Article 76. Accordingly, it constitutes the legal continental margin. The first sentence of paragraph 3 clearly provides that the bathymetric and mathematical formula contained in Article 76(4)(b) for identifying the foot of the slope is the general rule and can be waived only in the presence of evidence to the contrary.Footnote ²⁹ Thus, the textual construction of paragraphs 3 and 4 of Article 76 largely depend on bathymetric and morphologic parameters.Footnote ³⁰

The above is also an important element to bear in mind with regard to the interpretation of the second sentence of paragraph 3 of Article 76, pursuant to which the continental margin “does not include the deep ocean floor with its oceanic ridges or the subsoil thereof”.Footnote ³¹ This provision is the result of lengthy discussions during the Third Conference regarding the question whether elongated ridge-like features were capable of generating entitlements beyond the 200 M distance line from the baselines. In fact, in the first revision of the Informal Composite Negotiating Text [ICNT], the precursor of Article 76(3) did not include any reference to oceanic ridges. However, the paragraph was followed by a footnote reference which provided that “general understanding had been reached to the effect that on the question of underwater oceanic ridges there will be additional discussion and that a mutually acceptable formulation to be included in article 76 will be drawn up”.Footnote ³² The matter was further discussed during the eighth session of the Third Conference. Several proposals sought to limit the outer limits of the continental shelf to a 350 M distance line from the baselines where the seafloor high shared morphological characteristics of a ridge-like feature. The compromise crystallized during the ninth session, which led to the current formulation of paragraph 3 and the inclusion of the notion of “submarine ridges” in paragraph 5 bis to Article 76.Footnote ³³ The notion underwater oceanic ridges, to which the first revision of the ICNT referred, thus became two different and separate legal concepts: (i) the deep ocean floor with its oceanic ridges, and (ii) submarine ridges. It is noteworthy that the open compound oceanic ridges in the second sentence of paragraph 3 is preceded by the possessive determiner its, which refers to the subject deep ocean floor. This syntactic structure supports the interpretation that the determination of the continental margin is uniquely an exercise in determining its composite elements, rather than determining which parts on the seafloor are excluded from the continental margin; that is, the legal continental margin. It is the result of the former that determines the latter. Thus, there are no a priori parts of the seafloor which, due to their genome, are excluded from the legal continental margin, as paragraphs 3 and 4 “must be presumed to be the authentic expression of the intentions of the parties”.Footnote ³⁴ To quote the CLCS in its recommendations to the UK with regard to Ascension Island, “the existence of a continental slope requires the existence of a distinct morphological feature rising from the level of the continental rise or the deep ocean floor up to the continental shelf of the land mass of the coastal state”.Footnote ³⁵

The overwhelming practice of the CLCS lends support to the above understanding that geology has, in principle, no role in determining whether the entitlement of a coastal state to the continental shelf extends beyond 200 M.Footnote ³⁶ However, the recommendations to the Cook Islands can be considered a U-turn with regard to the CLCS understanding of Article 76(3)–(4) of UNCLOS.Footnote ³⁷ In those recommendations, the CLCS seeks to introduce a geological requirement in addition to the morphological and bathymetric requirements for the purposes of demonstrating that the submerged prolongation of the land mass extends beyond the 200 M area. In its view, “the key questions relating to natural prolongation” includes considerations such as whether “natural prolongation [can] be ensured morphologically and geologically from the islands to the base of the continental slope proposed in the Submission”.Footnote ³⁸ Thus, despite admitting morphological continuity with the land mass, the CLCS refused to accept that parts of the relevant seafloor highs were integral parts of the continental margin because of the failure of the submitting coastal state to demonstrate geological continuity with the land mass from which the seafloor high was the submerged prolongation. According to the CLCS, “only those seafloor highs for which a morphological and geological connection to the High Plateau could be clearly demonstrated should be considered part of the continental margin of the Cook Islands”.Footnote ³⁹ Accordingly, the CLCS appears to attach autonomous criteria to the notion of natural prolongation and makes the fulfilment of such criteria a condition precedent in order to constitute the continental margin.Footnote ⁴⁰ The CLCS observes that:

The approach pursued by the CLCS with regard to this particular submission finds no support in Article 76, and stands in contrast to the S&TGFootnote ⁴² and the previous practice of the CLCS,Footnote ⁴³ which is essentially based on morphology but which may also be coupled with geomorphology, if required under the particular circumstances.Footnote ⁴⁴ Further, it is also irreconcilable with the findings of the International Tribunal for the Law of the Sea [ITLOS] in the Bay of Bengal case where it held that “it finds it difficult to accept that natural prolongation referred to in Article 76, paragraph 1, constitutes a separate and independent criterion a coastal State must satisfy in order to be entitled a continental shelf beyond 200 [M]”.Footnote ⁴⁵ It will thus be considered that those recommendations of the CLCS are seen as a stand-alone approach, which will not form a precedent and which in any event cannot be seen to impact the conclusion that the definition of the continental margin does not depend upon any geological criteria. To summarize, the determination of the legal continental margin is exclusively a result of applying paragraphs 3 and 4 of Article 76. It is only the result of this exercise that determines which parts of the sea bed are part of the deep ocean floor with its oceanic ridges. This interpretation finds support in the travaux préparatoires.

2. Meaning of continental margin according to supplementary rules

Consistent with Article 32 of the Vienna Convention, “[r]ecourse may be had to supplementary means of interpretation, including the preparatory work of the treaty and the circumstances of its conclusion”.Footnote ⁴⁶ There can be no doubt that the enumerated means are not exhaustiveFootnote ⁴⁷ and are only subsidiary.Footnote ⁴⁸ Nevertheless, it may be difficult to determine the content of those means of interpretation, which are not enumerated in Article 32.Footnote ⁴⁹ Further, supplementary means of interpretation may only be relied uponFootnote ⁵⁰ in order to confirm the meaning of a treaty provision that arises from the application of Article 31 of the Vienna Convention on the Law of the Treaties, or “to determine the meaning when the interpretation according to article 31 (a) leaves the meaning ambiguous or obscure; or (b) leads to a result which is manifestly absurd or unreasonable”.Footnote ⁵¹ Courts and tribunals have only in rare cases admitted that a treaty interpretation pursuant to the general rule would lead to a manifestly absurd or unreasonable conclusion as a pretext for having recourse to Article 32 with a view to deviating from the understanding reached according to the general rule.Footnote ⁵² Against this background, Article 31 of the Vienna Convention is based on the understanding that a construction of a treaty provision pursuant to the general rule will in all situations determine whether an understanding of a treaty provision appears reasonable or whether it would lead to an unreasonable result from which it may be held that the criteria in paragraphs (a) and (b) in Article 32 can to a certain degree be seen as superfluous.Footnote ⁵³ This assertion is also made on the understanding that the “phrase ‘in the light of the object and purpose of the treaty’ had been inserted as an objective criterion in order to discourage disingenuous recourse to the notion of an ‘absurd’ interpretation”.Footnote ⁵⁴ Indeed, it is only in singular and rare situations that the criteria in Article 32(a)–(b) appear operative. Rather, the recourse to supplementary means of interpretation is by way of recourse to the rule contained in the chapeau of that provision, that is, to seek a confirmation in the travaux préparatoires that the interpretation pursuant to the general rule is a sustainable one.Footnote ⁵⁵

It has been observed that Article 76 of UNCLOS “is essentially a product of compromise—not consensus—between the conflicting positions of various groups which have different, and sometimes opposite, interests in the use of sea-bed areas”.Footnote ⁵⁶ This observation is symptomatic with regard to the unsuitability of relying on the travaux préparatoires for some provisions in Article 76.Footnote ⁵⁷ While this in general appears to be the case for paragraph 6 of Article 76 to some extent, it is not necessarily the case with regard to its paragraph 3. Widespread agreement that crystallized during the Third Conference resulted in geology being excluded from any constitutive role for the purpose of the inception of the notion of continental margin. In point of fact, during the Third Conference there were several proposals set forward providing for the contrary, but none of them received general support. Common to these proposals was the suggestion to include a criterion of continental crust in the definition of the continental margin. Some of these were explicit while others were implicit. In this regard, a proposal of the US is of interest as it appears to advocate a crustal requirement for the purpose of defining the continental margin:

The inclusion of the concept “rocks underlying the physiographic continental shelf, slope and rise” while excluding “rocks or the sediments of the deep ocean floor” appears to reflect a position according to which the continental margin depends on the nature of the rocks and sediments in question. The same approach is also apparently reflected in an informal proposal from the so-called Evensen group, which suggested that “the continental margin comprises the submerged prolongation of the said land mass, as well as the overlying sediments of the shelf, slope, and rise but does not include rocks and sediments appertaining to the deep ocean floor”.Footnote ⁵⁹

It would appear from the above proposal that those parts of the sea bed which do not share the same geological affinity with that of the land mass from which it is due to constitute the submerged prolongation are not constitutive of the continental margin. This arises in particular as it relies on the verb appertain when characterizing the sediments and rocks that do not belong to the continental margin. A proposal of Japan similarly suggested that the last sentence of paragraph 3 should provide that the continental margin did not include seafloor highs of oceanic crust consistent with which the continental margin “does not include the deep ocean floor or ridges formed of oceanic crust or the subsoil thereof”.Footnote ⁶⁰ Accordingly, it sought to exclude from the continental margin any feature according to predetermined geological criteria, notwithstanding the land mass composition from which the seafloor high was a submerged prolongation. The inclusion of such an understanding would be difficult to reconcile with the fundamental principle in the regime of the continental shelf that “the land dominates the sea”.Footnote ⁶¹ However, it was the proposal of Ireland which dissolved any such connotation as it excluded the verb appertain, and as such refrained from implying geological affinity with the land mass:

The proposal of Ireland did not contain any reference to rocks that are constitutive of the continental margin. Rather, it referred to the neutral wording “seabed and subsoil”. This proposal gained support and the proponents of the understanding of a legal continental margin, which excluded certain rocks from its material scope, rallied to this understanding of the continental margin. This proposal can be seen as the backbone of the doctrine of crustal neutrality.Footnote ⁶³ The Irish proposal was included in the first revision of the ICNT, together with its remaining part, which related to paragraph 4(a)–(b) of Article 76. Thus, the records show that, while some participants in the Third Conference sought to make the notion continental margin contingent upon a geological affinity with the land mass from which it extended, the outcome of this process resulted in the contrary. Geology was excluded as a constitutive criterion for the purpose of Article 76(3) of UNCLOS. On the contrary, the continental margin was made a neutral notion, which essentially relies on bathymetry and morphology. Accordingly, it can be concluded that the travaux préparatoires on Article 76(3) confirms the conclusion reached pursuant to the general rule of interpretation in making plain that the legal continental margin is essentially a morphological and bathymetric expression of the sea bed. Consequently, the continental margin is not contingent upon the demonstration of a geological affinity between the land mass and the seafloor highs that are the submerged prolongation from the relevant land mass.

1. Textual approach

According to Article 76(5), coastal states may use two constraints in the delineation of their outer limits. Thus, this paragraph sets forth a general principle consistent with which the constraints are alternatives, implying that the relevant coastal states may apply either of them, whichever appears more advantageous. In many situations, the depth constraint allows the establishment of more extensive outer limits of the continental shelf. However, Article 76(6) qualifies the interpretation of the preceding paragraph. According to Article 76(6):

The first sentence relates to submarine ridges on which the outer limits shall not exceed 350 M from the baselines. This is an exception, but yet, it is not an exception to the second sentence of paragraph 3, consistent with which the deep ocean floor with its oceanic ridges are not part of the continental margin, nor is it an exception to the second sentence of paragraph 6. It is only an exception to paragraph 5 of Article 76. The second sentence of paragraph 6 provides that the preceding sentence, consistent with which the outer limits shall not exceed 350 M on submarine ridges, does not apply to SENCCM, such as its plateaux, rises, caps, banks, and spurs. The question arises whether any seafloor high that is an integral part of the continental margin is a SENCCM in default of not constituting a submarine ridge, and vice versa, provided that these two categories would be mutually exclusive. Such a reading would, it appears, necessarily imply that any of the enumerated seafloor highs in the second sentence of paragraph 6 would ipso jure constitute a SENCCM. Thus, there would be no constitutive criteria to fulfil, provided the seafloor highs figure among those that are encapsulated in the non-exhaustive list in the second sentence of paragraph 6. The contrary could, quod non, in fact rely on an understanding that seafloor highs that obviously do not share ridge-like characteristics, such as plateaux, could potentially constitute submarine ridges within the meaning of the first sentence of paragraph 6. In support of this understanding, it could be argued that there was agreement in the first revision of the ICNT on paragraph 5 prior to the inception of paragraph 5 bis in the second revision of the ICNT. Thus, the participants had, arguendo, agreed that either of the constraints in paragraph 5 could be used in all situations. The first sentence in paragraph 6 is an exception to paragraph 5, while the second sentence would only be a safeguard clause seeking to limit the scope in the first sentence to only relate to ridges stricto sensu. Further, to assert that the second sentence of paragraph 6 would imply substantive criteria, other than being a safeguard clause vis-à-vis the first sentence in paragraph 6 would imply additional restrictions that were not intended by the participants as there was a priori agreement on paragraph 5 prior to the inception of paragraph 6. Yet, such a reading is difficult to support. Not only would it necessarily imply that the second sentence in paragraph 6 is superfluous, but that the ordinary meaning of the terms of paragraph 6, together with its context, object, and purpose, would not support a construction in accordance with which the first sentence in paragraph 6 is an exception to its second sentence. The object and purpose of the second sentence appear to support the two notions of submarine ridges and SENCCM as not mutually exclusive, as the second sentence embraces two typologies of seafloor highs: (i) SENCCM, and (ii) submarine elevations that are not natural components of the continental margin.

It will be recalled that the latter part of the second sentence of paragraph 6 enumerates a non-exhaustive list of seafloor highs that can be considered SENCCM. These are “plateaux, rises, caps, banks and spurs”.Footnote ⁶⁵ The use of “such as” prior to the above-mentioned enumeration makes it clear that the list in question is of a non-exhaustive nature. However, it would be erroneous to contend that any feature which falls within the category of the enumerated seafloor highs as such would necessarily constitute a SENCCM and thus allow an extension of entitlement beyond the 350 M distance line. Immediately subsequent to the inclusion of “such as”, referred to above, and immediately prior to the enumeration of the non-exhaustive list of seafloor highs, is included the possessive determiner “its”, whose subject is the continental margin: “This paragraph does not apply to submarine elevations that are natural components of the continental margin, such as its plateaux, rises, caps, banks and spurs.”Footnote ⁶⁶

An interpretation in accordance with which any of the non-exhaustive list of seafloor highs in the second sentence of paragraph 6 would necessarily constitute a SENCCM would disregard central provisions in the remaining part of that sentence to which the above-mentioned possessive determiner is an integral part. In this regard, it is also of interest to note that, during the ninth session of the Third Conference, Australia submitted a proposal with regard to paragraph 3 of Article 76, which suggested that the continental margin would “include submarine elevations which are natural components of the continental margin, such as plateaux, rises, banks and spurs”.Footnote ⁶⁷ It does appear that while this proposal related to paragraph 3, it may have been a direct source for the second sentence in paragraph 6 as it is retained almost verbatim therein. Yet, while the Australian proposal includes the open compound “such as”, it does not include the possessive determiner “its”. By way of illustration, paragraph 6 would have provided accordingly, were the possessive determiner not included: “This paragraph does not apply to submarine elevations that are natural components of the continental margin, such as plateaux, rises, caps, banks and spurs.”

The above would lend support to an understanding that any of the features which were listed in the second sentence of paragraph 6 were ipso jure SENCCM if the possessive determiner “its” was indeed omitted. This arises as the possessive determiner refers to the phrase “continental margin”. The object and purpose of the inclusion of the possessive determiner appears to support the assertion that geometry has no role for the purpose of the application of paragraph 6. It follows from the above that the enumeration of a non-exhaustive list of seafloor highs in the second sentence of paragraph 6 is not dispositive of which seafloor highs are natural components of a continental margin. This situation creates the challenge of how to interpret the second sentence of paragraph 6. The above assertion should also be seen in the light of the fact that the proposal of Australia with regard to paragraph 3 of Article 76 made use of the relative pronoun “which”, while paragraph 6 of Article 76 retained the relative pronoun “that”. Syntactically, this difference has substantive implications, although this distinction is more often noted in American English than in British English. The use of the relative pronoun “that” supports a more restrictive connotation than “which”. The latter is descriptive while the former indicates that none of the features which appear in the enumerated non-exhaustive list are necessarily SENCCM, but only those that are natural components of the continental margin. This arises as the relative pronoun “that” introduces a restrictive clause and not a mere parenthetical expression as the subsequent parts of the sentence depend upon it. If the second sentence of paragraph 6 were conceived on the relative pronoun “which”, the textual construction would allow an assertion that the open compound “submarine elevations” would be a stand-alone concept, as the parts of the sentence subsequent to the relative pronoun would only be descriptive of the open compound “submarine elevation”. Thus, if the relative pronoun “which” was included in paragraph 6, the remaining part of that sentence would provide additional descriptive information only. It would have read: “This paragraph does not apply to submarine elevations, which are natural components of the continental margin, such as its plateaux, rises, caps, banks and spurs.”

The above formula suggests that all submarine elevations are SENCCMs, as the relative pronoun “which” has a mere descriptive purpose by contrast to the use of the relative pronoun “that”, which introduces a restrictive clause. The open compound “submarine elevation” would be a typology of seafloor highs for the purpose of paragraph 6. Accordingly, it would not have been possible to assert that paragraph 6 of Article 76 provides a basis for three typologies of seafloor highs, as there would be only submarine ridges and submarine elevations. However, given the syntactic structure of the second sentence of paragraph 6, a seafloor high must be a natural component of the related continental margin in order to constitute a SENCCM, notwithstanding its general morphological characteristics. The second sentence of paragraph 6 therefore does not allow an interpretation according to which all features that are listed in the second sentence of paragraph 6 are necessarily SENCCM, as it would constitute a contra legem interpretation.Footnote ⁶⁸

2. Relevance of travaux préparatoires

Reliance on travaux préparatoires about the construction of ambiguous provisions in multilateral treaties is most often a difficult undertaking, in particular where discussions were not inclusive and conducted à huis clos.Footnote ⁶⁹ It is well known and documented that there were formal and informal negotiations during the Third Conference. Amendments to the negotiation texts were not set forward in accordance with ordinary principles applicable to most multilateral negotiations. The chairs of the main committees only addressed the plenary with amendment proposals if such proposals would increase the overall possibility for reaching agreement on a package deal. It is thus extremely difficult, if not impossible, to determine with reasonable certainty an intention enshrined among the participants that resulted in the approval or rejection of a particular position, at least insofar as it concerns texts, which were agreed on an exclusionary basis in closed foras. It is in such a context that the question arises whether the travaux préparatoires are able to reproduce a conclusive understanding, involving all states, in order to ascertain that the content of a document reflects the common intention of all participants.

It appears that the reason for the margineers actively, and a priori constructively, seeking to find a solution to the footnote reference to paragraph 3 in the first revision of the ICNT text, and the inclusion of paragraph 5 bis, was that they would most likely lose if the question was put to a vote. Thus, the argument that there was already general consensus on paragraph 5 during the discussions that resulted in the second sentence of paragraph 3 and paragraph 5 bis, from which it could be asserted that all features which are not submarine ridges sensu stricto are necessarily SENCCM, fails to take the above-mentioned important element into account. Further, a general dissatisfaction appeared during the ninth session about the manner in which the chair of the second committee considered proposals that were set forward regarding paragraph 5 bis. Singapore is quoted for having mentioned that these consultations:

In a more general statement, but reflecting the same concerns as Singapore, the delegate of Peru held:

A further statement of Singapore during the tenth session is also of particular interest in this regard, observing that:

The lack of response of other states to the proposals can be seen as affecting the assessment that a particular proposal reflected a certain wish of the participants to the Third Conference. An observation from a French scholar appears relevant in this context: “peut-on attendre ‘des travaux préparatoires’ autre chose qu'une explication, non pas du sens des mots, mais du ‘chaos’ terminologique auquel ils ont conduit?”Footnote ⁷³ The circumstances under which paragraph 5 of Article 76 was included in the first revision of the ICNT, in conjunction with the conditions prevailing at the inclusion of the then paragraph 5 bis in the second revision of the ICNT, question the very possibility of having recourse to the apparent fragmented sources from the travaux préparatoires on paragraph 6 of Article 76.

The interpretation of a multilateral treaty consists, to a large extent, in identifying the common intention of the participants. For obvious reasons, this task becomes more difficult if there are various, contradictory statements made.Footnote ⁷⁴ Referring to the travaux préparatoires under these circumstances, in particular in relation to such controversial provisions as paragraph 6 of Article 76 of UNCLOS, confirms the inconclusiveness of any common intention. Indeed, it appears that paragraph 6 of Article 76 is no exception insofar as “[i]n the case of multilateral agreements, the records of conference proceedings, treaty drafts, and so on may be confused or inconclusive”.Footnote ⁷⁵ The observations of ILC member Milan Bartoš, with regard to present Article 32 of the Vienna Convention, appear particularly lucid, and by way of analogy, are relevant with respect to compromise undertakings in multilateral conferences to which paragraph 6 of Article 76 of UNCLOS would be no exception:

It is uncontroversial that fragmentary excerpts from different sources may obviously lead to flawed understandings.Footnote ⁷⁷ The second sentence of Article 76(6) presents itself as a provision to which the travaux préparatoires may be of little use, not least because it fits with Philip Allott's now infamous comment that a treaty “is a disagreement reduced to writing”,Footnote ⁷⁸ the contours of which are agreed to on an exclusionary basis without any formal records. Therefore, the interrelations between the apparent typologies of seafloor highs in paragraph 6 of Article 76 need to be conducted according to the general rule of interpretation, the substantive meaning of which would clarify the constitutive criteria for SENCCM.

Accordingly, it can be concluded that the continental margin is subject to a legal definition, which does not attach geology as a constitutive criterion. Consequently, any areas of sea bed are susceptible to being integral parts of the continental margin, as determined by Article 76(3) and Article 76(4)(a)–(b) of UNCLOS.Footnote ⁷⁹ The same applies to ridge-like features, notwithstanding their crustal composition. It is exclusively the undertakings pursuant to the above-mentioned provisions that determine whether a ridge-like feature constitutes an integral part of the continental margin. However, the fact that a seafloor high is an integral part of the continental margin has no bearing on the question whether the seafloor high in question constitutes a SENCCM, and consequently allows either of the constraints under Article 76(5) of UNCLOS. Consistent with customary treaty interpretative rules, it is concluded that the first sentence of paragraph 6 of Article 76 is only an exception to Article 76(5). Further, the second sentence of paragraph 6 does not rely on geometry but rather makes contingent any classification of a seafloor high as a SENCCM that the seafloor high in question is a natural component of the continental margin. The fact that the second sentence of paragraph 6 relies on the possessive determiner “its”, in conjunction with the inclusion of the restrictive clause introduced by “that”, supports the assertion that the non-exhaustive list of seafloor highs in the second sentence of paragraph 6 is not dispositive of which seafloor highs are SENCCM. It is thus concluded that Article 76(6) does not rely on geometry.

1. Deficient incorporation in S&TG

A determination of constitutive criteria that determine which seafloor highs are SENCCM is premised on a proper understanding of Article 76(3), as the possessive determiner “its” in the second sentence of paragraph 6 refers to the notion continental margin. The latter concept is thus the topic of that part of the sentence, yet this does not provide a response to the question as to what criteria would constitute a SENCCM. A central consideration is how to conceive the concept “land mass”, the submerged prolongation of which seafloor highs must be natural components in order to constitute a SENCCM.Footnote ⁸⁰ The open compound “land mass” is an autonomous legal concept. The Concise Oxford English Dictionary defines “component” as “a part or element of a larger whole”.Footnote ⁸¹ If the open compound “natural component” is to have a substantive meaning other than “natural prolongation”, it can only be seen as a geological requirement, failing which the notion “natural component” would appear a tautological expression.Footnote ⁸² The reference to “natural component” in the second sentence must thus imply a higher affinity of the seafloor highs constituting the continental margin with the land mass from which it constitutes the submerged prolongation. It is asserted that the ordinary meaning of the open compound “natural component” in this context can only be read as referring to those parts of the sea bed which are an integral part and a derivative of the geological setting resulting in the creation of the land mass in question. This is also echoed in the relevant parts of the S&TG in which the CLCS has enumerated a list of criteria determining which seafloor highs are SENCCM:

The chapeau provision is clear in that the CLCS considers elements concerning the growth of continents determinant in relation to the classification of seafloor highs as SENCCM. Such elements are all of a geological nature. To paraphrase the CLCS, for the purposes of classifying seafloor highs as SENCCM, the determining factor is an understanding of how “continents grow”,Footnote ⁸⁴ and the growth of continents is primarily caused by “geological processes along the continental margins”.Footnote ⁸⁵ However, the above chapeau provision is supplemented with implementing principles for activeFootnote ⁸⁶ and passive continental margins only.Footnote ⁸⁷ The question arises whether it results from this provision that other typologies of continental margins cannot in the view of the CLCS constitute SENCCM, or at least not according to the same principles as those that are enshrined in point 7.3.1 of the S&TG. There is nothing in Article 76 that lends support to an understanding that the classification of seafloor highs as SENCCM is contingent upon whether the continental margin—the physical continental margin—is active or passive. The contrary would in fact imply that Article 76(6) of UNCLOS allows an exclusionary approach vis-à-vis the identification of continental margins that constitute SENCCM, which appears illusionary given that the continental shelf is a “legal concept”.Footnote ⁸⁸ It remains difficult to understand the reason for which the S&TG only relate to the above-mentioned continental margins when establishing substantive criteria for the purposes of classifying seafloor highs as SENCCM. This omission is particularly striking if comparison is made to the numerous physical continental margins that are listed in the S&TG in regard to other parts of Article 76.Footnote ⁸⁹ In any event, the exclusive reference to two typologies of continental margins in point 7.3.1 does not provide a legal basis for distinguishing between the particular typology of physical continental margins for the purposes of classifying these as SENCCM. Accordingly, regardless of the nature of the continental margin, the constitutive criterion for determining whether a seafloor high is a natural component of the continental margin remains geology.

The heading of point 7.3.1 of the S&TG calls for particular attention. It is entitled “submarine elevations”, rather than “submarine elevations that are natural components of the continental margin”. This single understanding of the notion submarine elevation also appears elsewhere in the S&TG.Footnote ⁹⁰ It is susceptible to raising more than one eyebrow as the syntactic structure of paragraph 6 of Article 76 does not provide a basis for asserting that the open compound “submarine elevation” is a stand-alone concept. Yet, more alarming is the fact that point 7.3.1 of the S&TG misquotes Article 76(6) of UNCLOS with regard to a matter of substance. According to point 7.3.1, “paragraph 6 includes a selection of highs: ‘such as plateaux, rises, caps, banks and spurs’. The phrase ‘such as’ implies that the list is not complete.”Footnote ⁹¹ It is apparent that the quotation incorrectly excludes the possessive determiner “its” immediately following “such as”. This can be seen as unfortunate given that, as mentioned earlier, the inclusion of this possessive determiner has substantive importance for the purposes of interpreting paragraph 6 of Article 76. The exclusion of the possessive determiner “its” from paragraph 6 would in significant terms change its meaning as it would lend support to an understanding that any of the enumerated features that appear in the non-exhaustive list are ipso jure SENCCM notwithstanding their relation to the land mass from which they represent the submerged prolongation.

It was established earlier that the negative definition in paragraph 3 of Article 76 does not allow an interpretation consistent with which crustal structure of a ridge-like feature, or any other feature for that matter, determines whether a seafloor high is an integral part of the continental margin within the meaning of the first sentence of paragraph 3. By contrast, a ridge-like feature with which there is no geological affinity with the land mass from which it constitutes the submerged prolongation cannot be considered a natural component of the continental margin in question as it could not be seen as a “natural component” of that particular continental margin. Conversely, there appears to be nothing to prevent a ridge-like feature from constituting a SENCCM provided the ridge-like feature is a natural component of the continental margin. Indeed, the notion “submarine elevation” appears in fact to be a mere elevation by reference to the adjacent areas on the seafloor. If the second sentence of paragraph 6 was interpreted in a manner in which the possessive determiner “its” was being ignored, it would result in the inextricable corollary that it would be more difficult to assert, for example, that seafloor highs with ridge-like characteristics could constitute SENCCM, notwithstanding that such a seafloor high would share geological affinities with the land mass. In fact, an understanding of paragraph 6 which disregards the possessive determiner “its” would be akin to attributing a quasi-tautological meaning to the relative pronoun “that” in the second sentence of paragraph 6. There is obviously no basis for assuming that the omission of the possessive determiner is the result of an intentional approach of the CLCS, as it directly and unambiguously represents a misreading of paragraph 6. In any event, the validity of any provision in the S&TG is contingent upon its strict conformity with Article 76 of UNCLOS.Footnote ⁹²

2. The nature of S&TG

The argument can be made that the S&TG are not binding upon State Parties to UNCLOS and thus the principles set forth in point 7.3.1 are not necessarily dispositive of the regime applicable to the classification of seafloor highs as SENCCM, at least not insofar as it concerns the legal contours for to that particular exercise. Such an assertion raises two questions: first, whether the CLCS is vested with powers that result in interpretations of Article 76 that become binding on State Parties to UNCLOS, and second, whether the CLCS is vested with powers to address matters other than those of a strictly technical and scientific nature. The fact that the CLCS is a treaty body composed of individuals that “serve in their personal capacities” makes it clear that the CLCS is vested with no prescriptive powers over State Parties’ rights under UNCLOS.Footnote ⁹³ Notwithstanding this uncontroversial point, the structure of UNCLOS is such that only those outer limits that are based on the recommendations of the CLCS are opposable in international law.Footnote ⁹⁴ Thus, while the S&TG are not legally binding stricto sensu, they are susceptible to being vested with normative characteristics, as it should be assumed that the CLCS will base its recommendations on this document.Footnote ⁹⁵ Point 7.3.1 would not, in principle, be an exception in this regard.

It should be recalled that a provisional version of scientific and technical guidelines was submitted to all states that had signed UNCLOS, with the opportunity of commenting on all the provisions therein before further consideration of the provisions by the CLCS.Footnote ⁹⁶ This exercise did result in changes to numerous provisions, but the predecessor to point 7.3.1 of the S&TG was identical in its terms; this is noteworthy. It is established case-law that “acquiescence is equivalent to tacit recognition manifested by unilateral conduct which the other party may interpret as consent”.Footnote ⁹⁷ Yet, it would be difficult to assert that the CLCS could be vested with the characteristics of “the other party”Footnote ⁹⁸ for the purpose of applying the doctrine of acquiescence in international law. This arises as it would necessarily imply that the rules governing acquiescence may be transposed mutatis mutandis to the legal relations governing the interactions between State Parties and the CLCS, the latter not being a subject of international law.Footnote ⁹⁹ On the other hand, it could be asserted that the submission of the provisional version of scientific and technical guidelines collectively “call[ed] for a response”Footnote ¹⁰⁰ to the extent that State Parties, for example, disagreed with the provision contained in point 7.3.1 regarding the classification of seafloor highs as SENCCM. In this regard, it should also be borne in mind that the adoption of the S&TG was undertaken pursuant to implicit powers of the CLCS, the exercise of which were considered essential for the CLCS to fulfil its mandate.Footnote ¹⁰¹ Further, it is also noteworthy that, during the Eleventh Meeting of State Parties to UNCLOS, it was observed that the principal reason for altering the ten-year period in Article 4 of Annex II to UNCLOS was the understanding that it was only “after the adoption by the [CLCS] of its [S&TG] on 13 May 1999 that States had before them the basic documents concerning submissions in accordance with Article 76, paragraph 8, of the Convention”.Footnote ¹⁰² By that decision, it appears axiomatic that the State Parties expressed general agreement on the necessity of the S&TG for the purpose of understanding Article 76, including the premise underlying point 7.3.1, insofar as it concerns the second sentence of paragraph 6, namely that geological criteria determine whether a seafloor high can be classified as a SENCCM.Footnote ¹⁰³

The S&TG are not constitutive of a subsequent agreement within the meaning of Article 31(3)(a) of the Vienna Convention, because the guidelines were not adopted by the State Parties to UNCLOS but by the CLCS. However, the material provisions in the S&TG can be seen as vested with normative characteristics, given that the S&TG “form the basis for the [CLCS] to make its recommendations with respect to submissions prepared by states according to Article 76”.Footnote ¹⁰⁴ The above appears clearly in light of the fact that its provisions are not limited to technical aspects stricto sensu. The S&TG provide that their aim is to:

Thus, it appears that, according to the S&TG, the obligation incumbent upon the CLCS—according to its terms of referenceFootnote ¹⁰⁶—does also entail considerations which are not necessarily limited to technical aspects.Footnote ¹⁰⁷ Consequently, the above-mentioned provisions in the S&TG that relate to constitutive criteria for classifying seafloor highs as SENCCM may be based not only on scientific and technical aspects but also on the legal foundations underlying Article 76. This is symptomatic of the fact that the outcome of the considerations that the CLCS undertakes in relation to the various submissions cannot be underestimated. Further, the above aspects become even more obvious given that the opposability of the establishment of outer limits is contingent upon such limits being based on recommendations of the CLCS.Footnote ¹⁰⁸ Whereas the S&TG are unable to constitute subsequent agreement, they can, in conjunction with the recommendations, which themselves are due to be based on the S&TG, encourage states to align their reasoning to the principles enshrined therein in order to ensure approval by the CLCS. Thus, by default of not constituting a subsequent agreement, the S&TG may be the source of subsequent practice within the meaning of Article 31(3)(b)Footnote ¹⁰⁹ of the Vienna Convention.Footnote ¹¹⁰ Any such subsequent practice of State Parties to UNCLOS would necessarily assume uniform practice of the CLCS on this particular question. However, as will be demonstrated below, the practice of the CLCS differs in a non-negligible fashion with respect to its undertakings on the classification of seafloor highs as SENCCM.

In conclusion, it is apparent that the S&TG have misquoted Article 76(6) of UNCLOS when listing the criteria governing the classification of SENCCM. This arises as the CLCS omits the possessive determiner “its” when quoting Article 76(6), which, if read literally, could give rise to an assertion that the enumerated list of seafloor highs in the second sentence of Article 76(6) is dispositive of which seafloor highs are SENCCM. However, such a construction would lack a legal foundation as it would counter an interpretation of Article 76(6) that is done in a manner consistent with customary treaty interpretative rules in accordance with which geometry has no role for the purposes of classifying a seafloor high a SENCCM. In any event, the S&TG are unable to prevail over the primary source, which is UNCLOS. In fact, the misquotation of Article 76(6) in point 7.3.1. of the S&TG can emphasize the importance that should be attributed to the inclusion of the possessive determiner “its” in the second sentence of paragraph 6 of Article 76.

1. Interrelations of typologies of seafloor highs in paragraph 6

In the recommendations of the CLCS to Australia, it appears that Australia, the submitting coastal state, was of the view that the second sentence of paragraph 6 of Article 76 is based on geometry. Australia asserted that “[b]ased on morphology only, Australia holds the view that the Wallaby-Composite High is not a ridge”,Footnote ¹¹¹ assuming consequently that the feature in question is a SENCCM. The same approach was also reflected with regards to the Joey Rise.Footnote ¹¹² The question arises whether it should consequently follow that these seafloor highs are necessarily SENCCM, in the absence of not sharing ridge-like characteristics. The apparent approach of Australia lends support to the understanding that, in its view, there are only two typologies of seafloor highs in paragraph 6, which are mutually exclusive. Further, in any event, the classification of SENCCM is contingent upon geometry, that is, the morphological shaping of the seafloor highs in question may determine whether the features are encapsulated by the enumerated list in the second sentence of paragraph 6. However, with regard to the Wallaby-Composite High, Australia had also provided geological data and information in support of its putative classification. The CLCS agreed that, on the basis of the evidence presented by Australia, it “is to be regarded as a [SENCCM] qualifying for the application of the depth criterion constraint”.Footnote ¹¹³ While the Wallaby-Composite High was considered eligible to make use of the depth constraint, the CLCS dismissed the application on the Joey Rise as it did “not consider it proven that the Joey Rise should be regarded as a [SENCCM]”,Footnote ¹¹⁴ notwithstanding the fact that “the Joey Rise is part of the submerged prolongation of the landmass of Australia and, as such, is part of the continental margin of Australia”.Footnote ¹¹⁵ The CLCS did not elaborate on whether the Joey Rise consequently was necessarily a submarine ridge in default of not constituting a SENCCM, but it did observe that, as a result of not constituting a SENCCM, the Joey Rise did not “qualify for the application of the depth criterion constraint”.Footnote ¹¹⁶ Consequently, the CLCS did not seek to elaborate on the nature of the interrelations of the two paragraphs in Article 76(6) of UNCLOS, but contented itself with determining that Australia had not discharged its onus to document that the Joey Rise is a SENCCM. In any event, from a morphological point of view, it is difficult to disagree with Australia that the Joey Rise cannot easily be considered to share ridge-like characteristics.Footnote ¹¹⁷ Assuming that the CLCS would not disagree on this, not accepting its classification as a SENCCM supports the assertion that the CLCS does not consider that the enumerated list of seafloor highs in the second sentence of paragraph 6 are dispositive of which seafloor highs are SENCCM.Footnote ¹¹⁸ A similar approach appears also in the CLCS's recommendations to Norway with regard to the classification of the Vøring Spur. In the view of the CLCS, the information presented by Norway, the submitting coastal state:

It did not seek to further classify the Vøring Spur; namely, whether in the absence of not constituting a SENCCM it would be a submarine ridge, or a submarine elevation which is not a natural component of the continental margin. Thus, according to this line of thinking by the CLCS, paragraph 6 would not necessarily be based on two legal categories of seafloor highs that are mutually exclusive.

In its recommendations to Japan, the CLCS revisited its approach on the interrelations of the typologies in paragraph 6. The CLCS noted that the Ogasawara composite high is the submerged prolongation of the land territory of Japan, and thus constitutes the continental margin within the meaning of paragraph 3 of Article 76.Footnote ¹²⁰ According to Japan, the entire seafloor high should be considered a SENCCM. The CLCS agreed that the “Plateau part of the composite high may be considered a [SENCCM] in the sense of Article 76”, but did not share Japan's views concerning the putative classification of the remaining part of the seafloor high.Footnote ¹²¹ According to the CLCS:

Whereas the CLCS refers to a so-called “Ridge Part”Footnote ¹²³ of the Ogasawara composite high, this feature did not appear to share significant morphological differences in comparison to the Joey Rise.Footnote ¹²⁴ It is also important to have in mind that Australia also provided seismic data in support of its classification of the Joey Rise as a SENCCM. Yet, according to the CLCS:

It is thus clear that the approach of the CLCS in its considerations of Japan's submission is singular with respect to its conception of the interrelations of the first and second sentences in Article 76(6) of UNCLOS. Be that as it may, according to this line of thinking it would appear that the first sentence of paragraph 6 is an exception to the second sentence of paragraph 6, rather than being an exception to paragraph 5. This arises as the CLCS expresses the view that in default of not constituting a SENCCM the feature in question is necessarily a submarine ridge within the meaning of the first sentence of paragraph 6.Footnote ¹²⁶ It has been argued earlier that the syntactic structure of paragraph 6 does not allow such a construction. This arises as the first sentence of paragraph 6 of Article 76 is an exception to Article 76(5) only. Given that the second sentence qualifies the classification of any seafloor high as a SENCCM, it would be erroneous to assert that, in the absence of not fulfilling the substantive criteria in order to be classified as a SENCCM, the feature in question would necessarily constitute a submarine ridge. Such reasoning would only be legitimate if geometry is a constitutive criterion for the purposes of classifying seafloor highs as SENCCM. However, attributing geometry such a role has no legal foundation.

A different approach appeared in the recommendations of the CLCS to France on its submission relating to the Kerguelen Island. According to France, Gallieni Ridge was a SENCCM. However, in the view of the CLCS, it was arguable that the Gallieni Ridge shared geological affinity to the Kerguelen Plateau from which it was a seaward prolongation, but that it could also be considered as geologically relating the surrounding deep ocean floor. Thus, rather than constituting a SENCCM, the Gallieni Ridge could “be classified as a submarine ridge”.Footnote ¹²⁷ Yet, the CLCS added in this regard that the available data was not conclusive and consequently “it was not in a position to decide on such a classification of the Gallieni Ridge”.Footnote ¹²⁸ Accordingly, the CLCS did “not consider it proven, based on the data provided, that the Gallieni Ridge should be regarded as a [SENCCM] in the sense of Article 76, paragraph 6”.Footnote ¹²⁹ The approach embraced in this recommendation resonates with the approach undertaken in the recommendations to Japan. The CLCS conceives of paragraph 6 as based on two typologies of seafloor highs. The CLCS was, however, less categorical to the extent that it did not consider the Gallieni Ridge to be a submarine ridge because of the apparent uncertainties which arose in the absence of “geochemical samples … to compare with the Kerguelen Plateau”, although it “seems likely that the ridge did propagate from the Kerguelen Plateau, and as such the ridge and the plateau should have a similar geochemical character”.Footnote ¹³⁰

The recommendations of the CLCS to Iceland are somehow singular in its classification of the Reykjanes Ridge. The CLCS confirmed its understanding that the depth constraint “may be applied to those parts of the continental margin that are classified as natural components of that margin”.Footnote ¹³¹ Iceland invoked only the depth constraint vis-à-vis the establishment of a constraint line on the Reykjanes Ridge. By majority voting, the subcommission established to consider the submission of Iceland approved the application of the depth constraint. Thereby, it must be assumed that it agreed that the Reykjanes Ridge is a SENCCM. However, there was disagreement on this particular question among the members in the plenary session of the CLCS, where some “members of the [CLCS] arrived at the conclusion that the data and information contained in the Submission did not support its consideration as a submarine elevation”.Footnote ¹³² It was not possible to gather the required majority to approve the draft recommendations of the subcommission.Footnote ¹³³ Therefore, the CLCS was compelled to find the lowest common denominator, which resulted in the expression that it recommended “only those fixed points constituting the outer limits of the continental shelf that are located within 350 M from the baselines from which the breadth of the territorial sea of Iceland is measured”.Footnote ¹³⁴ It is obvious that the CLCS refrained from even insinuating that the Reykjanes Ridge is a submarine ridge, notwithstanding the fact there was apparent agreement that the submitted data and information did not allow its classification as a SENCCM. The approach undertaken in its consideration of the submission of Iceland thus reflects a deviation from the CLCS's recommendations to Japan, and its recommendations to France with respect to the Kerguelen Island. Although it is obvious that the Reykjanes Ridge does share ridge-like characteristics, the CLCS did not draw the same conclusion as it did in the above-mentioned cases.

Consequently, it follows that the CLCS has not managed to establish a uniform understanding with regard to the interrelations of the two sentences in paragraph 6. On the one hand, it considers the first sentence of paragraph 6 an exception to the second sentence, but yet there appears to be no legal foundation which justifies such an understanding. On the other hand, the CLCS is ambiguous with regard to the consequences in situations where it dismisses the classification of seafloor highs that do not share ridge-like characteristics. It thus embraces a practice which leaves ambiguity as to whether such features are necessarily submarine ridges or whether they can be considered submarine elevations that are not natural components of the continental margin.

2. Constitutive criteria

It is clear from the practice of the CLCS that the main criterion to determine whether a seafloor high is a SENCCM, and therefore eligible to use the depth constraint, is geology. The CLCS seeks to determine whether there is geological affinity with the land mass throughout those parts of the margin that allegedly are SENCCM. Thus, the approach of the CLCS appears aligned with the principles set forward in the S&TG regarding classifications. Its consideration of the submission of Australia and of the partial submission of France in regard to the New Caledonia region are representative in this regard. The CLCS scrupulously examined the evidence that the submitting coastal states presented on the classification of the relevant seafloor, notwithstanding the plateau-like characteristics of the seafloor highs in question. In its recommendations to France, the CLCS made the classification of the Lord Howe Rise, which can by no means be considered to share ridge-like characteristics, contingent upon the demonstration that there was geological affinity with the overseas territories that generated entitlement. The CLCS observed that the “Lord Howe Rise and its northern extension is of continental origin that is well evidenced by deep sea drilling data, seismic reflection/refraction studies, and gravity modelling”.Footnote ¹³⁵ Consequently, the Lord Howe Rise was considered a SENCCM “in the sense of Article 76, paragraph 6, and in accordance with paragraph 7.3.1.b of the [S&TG]”.Footnote ¹³⁶

Thus, the fact that the above-mentioned seafloor highs could textually correspond to the features listed in the non-exhaustive list in the second sentence of paragraph 6 is not dispositive of anything. Accordingly, it follows that the CLCS does attach importance to the possessive determiner “its” in the second sentence of paragraph 6, although it was missing in the relevant parts in the S&TG. Conversely, it also follows that the CLCS does not consider geometry relevant for the purpose of classifying plateau-like features. Notwithstanding the fact that the seafloor high in question shared plateau-like characteristics, it did not exempt the submitting coastal state from the obligation of demonstrating that the seafloor high in question shared geological affinity with the relevant land mass.

A similar approach is also clearly apparent in the recommendations of the CLCS to Australia concerning the Exmouth Plateau. The CLCS assessment was “[b]ased on the geological and geophysical data provided”, with which it agreed:

Thus, it is also apparent in these recommendations that the enumerated list of seafloor highs in the second sentence of paragraph 6 is not dispositive of which seafloor highs are SENCCM.

In its recommendations to Norway, the CLCS adopted a similar approach vis-à-vis the putative classification of the Jan Mayen Micro-Continent/Iceland Plateau. This arises as the classification of this plateau-like seafloor high was made contingent upon the demonstration of geological affinity between the seafloor high and the land mass from which it is the submerged prolongation, notwithstanding the indisputable fact that the seafloor high in question cannot be considered to share ridge-like characteristics. The CLCS observed that:

It is apparent that there is a deviation from its approach above in the recommendations to Argentina. The CLCS did not follow the same procedure with regard to the classification of the Rio de la Plata Craton passive volcanic continental margin. First, the CLCS noted that “[f]or the outer limits of the continental shelf in the Rio de la Plata Craton passive volcanic continental margin region, Argentina invoked a combination of the depth and distance constraints”.Footnote ¹³⁹ Thus, it is apparent that Argentina considered the relevant seafloor high a SENCCM. Second, it was noted that the CLCS “agreed with the procedure and accuracy by which the 2,500 m isobath and the depth constraint at a distance of 100 M from it had been determined”.Footnote ¹⁴⁰ There is no reference to an assessment of whether the seafloor high in question was a natural component of the continental margin. It is reasonable to assume that, for reasons related to the determination of the relevant foot of continental slope points, the result of that undertaking would be self-evident.Footnote ¹⁴¹ However, it is unfortunate that the CLCS waived its otherwise consistent approach to make the classification of a seafloor high contingent upon the fulfilment of the criteria in point 7.3.1 of the S&TG, notwithstanding the fact that the relevant seafloor high shared morphological characteristics similar to a geomorphic shelf.

The question whether ridge-like characteristics are eligible to constitute a SENCCM has been given ample consideration in the deliberations of the CLCS. The overwhelming practice of the CLCS demonstrates an inclination to consider any ridge-like feature eligible to constitute a SENCCM. The determining factor in this regard is whether such seafloor highs share geological affinity with the land mass from which they are submerged prolongations. Whether the continental margin is active or passive appears immaterial. This appears clearly in the recommendations to Australia.

First, the CLCS observed that the Southern Kerguelen Plateau [SKP] and the Central Kerguelen Plateau [CKP]:

Second, it considered whether it was demonstrated that the Williams Ridge [WR] is a SENCCM. The CLCS was unable to accept such a classification sought by Australia as “the geological origin of the Williams Ridge still remains unresolved”.Footnote ¹⁴³ The CLCS therefore concluded that it “does not consider it justified that the WR is regarded as a [SENCCM] in the sense of Article 76, paragraph 6, qualifying for the application of the depth criterion constraint”.Footnote ¹⁴⁴ The WR clearly resembles a ridge-like feature, but this did not prevent the CLCS from considering its classification as a SENCCM admissible. The reason for declining its putative classification as a SENCCM was exclusively due to Australia's failure to demonstrate that the constitutive criteria were fulfilled. The recommendations to France in respect of the classification of the Gallieni Ridge follows the same reasoning. The fact that the Gallieni Ridge shared geometric characteristics similar to a ridge did not prevent its putative classification as a SENCCM from being inadmissible. The sole reason for dismissing the classification, which was sought by the submitting coastal state, was due to the failure to demonstrate that it shared geological affinity with the land mass from which it was the submerged prolongation.Footnote ¹⁴⁵

In its summary of recommendations to Japan, the CLCS appears to disclose elements of its internal deliberations, which hitherto have not been reflected in its public documents. The CLCS referred to point 7.3.1(a) of the S&TG in accordance with which “any crustal fragment or sedimentary wedge that is accreted to the continental margin should be regarded as a natural component of that continental margin”.Footnote ¹⁴⁶ The CLCS concluded accordingly that “[t]his consequentially implies that those parts of any crustal fragment or sedimentary wedge that are morphologically connected but not (yet) accreted to the continental margin are not to be regarded natural components of that margin”.Footnote ¹⁴⁷ The CLCS observed thereafter that, notwithstanding the morphological connection of the Ridge Part with the Ogasawara composite high, it is “not involved in the tectonic accretion process and, as such represent a subsidiary feature of the plateau that is not in itself accreted to the Izu-Ogasawara Arc”.Footnote ¹⁴⁸ On this basis, the CLCS dismissed its classification as a SENCCM sought by the submitting coastal state. A deviation from the above approaches appears in the recommendations to Iceland concerning the classification of the Reykjanes Ridge as a SENCCM. According to Iceland, Reykjanes Ridge is a SENCCM notwithstanding its obvious ridge-like characteristics, but this classification was dismissed by the CLCS. It appears overwhelmingly clear that the sole reason for the CLCS's decision not to accommodate the view of Iceland related to an understanding that a seafloor high akin to the Reykjanes Ridge is unable to constitute a SENCCM, notwithstanding prevailing geological history. This reasoning stands in clear contrast to the prior statements of the CLCS. The CLCS held that “the data and information contained in the Submission were inconclusive to support the western and southern parts of the Reykjanes Ridge as a natural component of the continental margin of Iceland”.Footnote ¹⁴⁹ However, in contrast to other situations in which submitting coastal states have sought to classify ridge-like features as a SENCCM, there is no further elaboration on this particular aspect of substance in its recommendations of Iceland other than that the data was “inconclusive”.Footnote ¹⁵⁰ Thus, it is clear that there are deviations in the approaches of the CLCS on these important undertakings with regard to classifications of seafloor highs as SENCCM.

It follows from the above that it is fair to assert that the practice of the CLCS on classification of seafloor highs as SENCCM is not uniform. The lack of uniformity is two-fold. On the one hand, there are methodological inconsistencies. It is apparent that the CLCS is embracing a non-uniform approach with regard to the interrelations of the first and second sentences of paragraph 6 of Article 76, the consequences of which are not at all negligible as they may impact substantive considerations in classification undertakings. On the other hand, while the CLCS appears to approach the classification of seafloor highs with an understanding that does not pay attention to geometry, there have been unfortunate deviations from this approach, which raises insecurity over the question of the classification of seafloor highs.