A Commentary on the 2023 Nicaragua v Colombia case  

On 13 July 2023, the International Court of Justice (ICJ or the Court) handed down its long-awaited judgment on the merits in the Nicaragua v Colombia case concerning the delimitation of the continental shelf beyond 200 nm. An overview of the judgment and observations upon it by Hilde Woker have already been posted on this blog. This comment builds on this, and offers some additional observations concerning its implications, in particular for maritime boundary delimitation. From the outset, this has been a difficult case for the Court, and it is worth recalling that the Court upheld its jurisdiction to adjudicate the matter in a controversial judgment in 2016 to which seven judges appended a joint dissenting opinion, while Judge Donoghue added an individual dissenting opinion.

It is also important to remember that the question which the Court now answers in its recent judgement is a question which the Court itself, and not the parties, formulated: in its Order of 04 October 2022, it formulated the following two questions:

(1) Under customary international law, may a State’s entitlement to a continental shelf beyond 200 nautical miles from the baselines from which the breadth of its territorial sea is measured extend within 200 nautical miles from the baselines of another State?

(2) What are the criteria under customary international law for the determination of the limit of the continental shelf beyond 200 nautical miles from the baselines from which the breadth of the territorial sea is measured and, in this regard, do paragraphs 2 to 6 of Article 76 of the United Nations Convention on the Law of the Sea reflect customary international law?

In its recent judgment, the Court answered the first of its questions in a way which rendered the second question redundant: it determined that it is not permissible for a State to assert continental shelf rights to areas beyond 200 nm from the baselines from which its territorial sea is measured to areas which lie within 200 nm of the baselines of another State. As it turns out, this now appears to be a very clear answer to a poorly phrased question which leaves some important questions unresolved, whilst opening up several new and difficult questions which now will need to be answered.

It should also be remembered that a Special Chamber of the International Tribunal for the Law of the Sea (ITLOS) recently had the opportunity to provide an answer to the same question in the Mauritius/Maldives case. The Special Chamber noted that following its drawing of a single maritime boundary for the continental shelf/EEZ between the parties there were in fact no areas remaining to be delimited which were within the 200 nm limit of either party. As a result, it thought that:

‘neither Party may claim or exercise sovereign rights or jurisdiction with respect to the exclusive economic zone or the continental shelf within the 200 nm limit of the other Party on the latter’s side of the boundary.’

Accordingly, the Special Chamber saw no need for it to answer this thorny issue. As a result, we are spared – for now at least – the awkwardness of the ICJ and ITLOS taking different approaches to this.

As we argue in a forthcoming book chapter, we believe that the Court took the correct approach to the question it had asked. The Court finally accepted that the basis of entitlement to the single continental shelf is not itself singular: it said that the basis of entitlement to a continental shelf within 200 nm is based on distance, whereas the basis for entitlement to a continental shelf beyond 200 nm is based on natural prolongation. This paves the way for its principal finding that within 200 nm a continental shelf based on natural prolongation takes second place to a continental shelf based on distance.

Given that both the LOSC and international jurisprudence have accorded primacy to the distance criterion over natural prolongation within 200 nm when delimiting overlapping entitlements to continental shelves and EEZs (1985 Libya/Malta), it follows that a State’s claims concerning the continental shelf beyond 200 nm, which are based on the existence of natural prolongation, cannot ‘trump’ the rights of another State within 200 nm from its baselines.  

It is now generally ignored that the entire point of the distance-based claim to a continental shelf was to allow those States which did not have a ‘natural’ continental shelf to be able to claim entitlement to areas of seabed to which it otherwise would have had no entitlement. What this judgment has done is finally turn this on its head: priority is now given to claims based on distance, not to claims based on natural prolongation. Indeed, it is not just ‘priority’. The distance-based claim, in effect, ‘expunges’ claims that are not based on distance – and in the light of the development in the jurisprudence over the years this is without doubt the right approach. But the implications are profound, and largely ignored by the Court.

It would, for example, have been useful for the Court to admit that it was, in effect, ‘overruling’ the North Sea cases on this point. This must be the case, and it might have been as well for the Court to have said so – though that was always unlikely. But a more detailed exploration of other implications might have been expected.

And the bottom-line problem which now will have to be faced is ‘200 nm from what’? The Court says ‘from the Nicaraguan coast’, since this is the (poorly worded) question it set out to answer.  In reality, maritime zones are not measured from ‘coasts’ but from baselines (which may or may not also be coasts). And not all baselines generate claims to a 200 nm zone. As a result, the need to distinguish between ‘islands’ and ‘rocks’ which cannot claim extended zones by virtue of Article 121(3) LOSC and those that can becomes even more acute. It is also obvious that, because of Article 121(3) LOSC, it is not true to say that claims cannot be made to areas within 200 nm of the ‘coasts’ of another State – why should a State not be entitled to make a claim to an area which another State is not entitled to, even if it is within 200 nm of its coast? All this does is foreground difficult questions of the entitlement of small maritime features which had previously been ‘washed up’ (and thus left unanswered) when conducting maritime delimitations. Thanks to this judgment, that convenient route of avoiding those hard questions has been extinguished – and not only in relation to claims concerning shelves beyond 200 nm.

Is it really going to be the case that such maritime features might not have much of an impact when a delimitation line drawn between two States whose 200 nm zones overlap, but they might have a far greater impact when it comes to preventing a State situated more than 200 nm miles away from making a claim at all? Countries with very small islands situated at a distance from their mainland coasts may now find that their value in generating ocean space is considerably enhanced, and this may exacerbate tensions over their ownership. Indeed, in its 2012 judgment in this very case the ICJ failed to give full effect in a delimitation to islands which, on the basis of its 2023 judgment, would have been entitled to expunge competing claims, and remove the need for a delimitation altogether.

There are other general potential implications for delimitation between States within 400 nm of each other if, as the Court suggests, the distance principle is to be given an enhanced status: or is this prioritising solely reserved for questions of entitlement and not for matters concerning delimitation? Certainly, there is a clear trend to ignore for the purposes of delimitation the baselines used by States for generating their territorial sea, as courts feel free to choose their own basepoints and baselines. Can a State claim 200 nm from a baseline or basepoint which the Court subsequently decides is not to be used for generating an equidistance (or any other) form of line?

And then there are questions concerning grey areas – are these now compatible with this statement of customary international law: the very idea of a grey zone implies that the zone of one State following a delimitation includes an area which is beyond 200 nm from its coasts but within 200 nm of coasts of another. Is this now possible? The Court recalled its important finding in the Libya/Malta case that the continental shelf and the EEZ concepts are ‘interrelated’ and that ‘[a]lthough there can be a continental shelf where there is no exclusive economic zone, there cannot be an exclusive economic zone without a corresponding continental shelf’. These pronouncements were, to a great extent, overlooked in the Bay of Bengal cases, as well as by the ICJ itself in the Somalia v Kenya case. However, the Court now stressed that the circumstances in the Bay of Bengal cases were very different, while in the Somalia v Kenya it had merely hinted at the possibility of the creation of a ‘grey area’.

It is fair to say that there is now that ‘grey zones’ have become a something of a ‘grey area’ in law. It is noticeable that some of the dissenting judges spoke in favour of them (Judge Tomka, Judge Xue), clearly suggesting that they recognised their incompatibility with the judgment of the Court. Indeed, it may be that the logic of the Court’s judgment makes it very hard to justify departures from the strict median line generated from coastlines/baselines from which claims to 200 nm zones can be made. After all, distance implies equidistance, and always has.

The Court has commendably refused to fudge its answer to the question here: but will it fudge the consequences of its answer? We hope not, but it probably will: after all, logic and transparency have hardly been the leitmotivs of the Court’s jurisprudence on this topic over the last 65 years, or thereabouts.