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(a) the rules and principles of international law for the determinations referred to in Article
3(1)(a); (b) international law, equity and the principle of good neighbourly relations in
order to achieve a fair and just result by taking into account all relevant circumstances for
the determinations referred to in Article 3(1)(b) and (c).
This distinction calls for two preliminary remarks. First, the fact that the course
of the maritime boundary within and outside the Bay of Piran had to be determined
strictly in accordance with the “rules and principles of international law”, does not
mean that the identification of those rules and principles was, in itself, uncontroversial. Indeed, Croatia claimed that the applicable rule governing the determination of
the entire course of the maritime boundary was Article 15 UNCLOS (i.e., the equidistance/special circumstances rule), based on the argument that the waters within
and outside the Bay of Piran had to be considered territorial sea; whereas, Slovenia
relied on three alternative arguments in order to claim that the totality of the waters
of the Bay were Slovenian internal waters. As I will attempt to show, while it is
debatable whether there is a rule of customary international law under which bays
bordered by two or more States can be included in the internal waters of riparian
States, equally debatable is the question of what rule or principle should be applied
in delimiting the internal waters between States whose coasts are opposite or adjacent to each other. As a consequence, the Arbitral Tribunal’s decision to qualify the
waters of the Bay as internal waters, and to proceed with their delimitation by
applying the principle of uti possidetis juris, is not entirely convincing. Similarly,
the Tribunal’s interpretation and application of Article 15 UNCLOS in delimiting
the territorial sea boundary in the Gulf of Trieste has attracted some criticism from
commentators.
27
Secondly, the distinction in Article 4 reflects, among other things, the difficulties
encountered by the Parties in their previous bilateral attempts to resolve what
seemed to be the most controversial issue at stake, namely Slovenia’s claim to have
direct territorial access to the high seas. By requiring the Arbitral Tribunal to rely on
“equity and the principle of good neighbourly relations” in order to “achieve a fair
and just result” with respect to that issue, the two States arguably imparted the necessary flexibility to the arbitration process, in view of the final settlement of the
dispute between them. This is confirmed by the fact that the Tribunal had to apply
this broader set of rules and principles also in determining the regime for the use of
all “the relevant maritime areas”—i.e., not only the “junction” area, but also the
other, previously delimited, maritime areas between the two countries, and especially those within the Bay of Piran (which, in the aftermath of the adoption of the
Final Award, seem to have become the source of renewed tension between the two
States).
The Final Award of 29 June 2017 clearly distinguishes between, on the one hand,
determinations in respect of the Piran Bay and, on the other hand, determinations in
respect of other maritime areas. The Arbitral Tribunal proceeded first by: defining
27 Vidas (2018), pp. 58–61, for instance, notes that the Final Award of 29 June 2017 “fully confirms - and further aggravates - the reasons for concern expressed here about some recent trends in
case law on the territorial sea delimitation”.
The Law of Maritime Delimitation in the Croatia/Slovenia Final Award
(a) the rules and principles of international law for the determinations referred to in Article
3(1)(a); (b) international law, equity and the principle of good neighbourly relations in
order to achieve a fair and just result by taking into account all relevant circumstances for
the determinations referred to in Article 3(1)(b) and (c).
This distinction calls for two preliminary remarks. First, the fact that the course
of the maritime boundary within and outside the Bay of Piran had to be determined
strictly in accordance with the “rules and principles of international law”, does not
mean that the identification of those rules and principles was, in itself, uncontroversial. Indeed, Croatia claimed that the applicable rule governing the determination of
the entire course of the maritime boundary was Article 15 UNCLOS (i.e., the equidistance/special circumstances rule), based on the argument that the waters within
and outside the Bay of Piran had to be considered territorial sea; whereas, Slovenia
relied on three alternative arguments in order to claim that the totality of the waters
of the Bay were Slovenian internal waters. As I will attempt to show, while it is
debatable whether there is a rule of customary international law under which bays
bordered by two or more States can be included in the internal waters of riparian
States, equally debatable is the question of what rule or principle should be applied
in delimiting the internal waters between States whose coasts are opposite or adjacent to each other. As a consequence, the Arbitral Tribunal’s decision to qualify the
waters of the Bay as internal waters, and to proceed with their delimitation by
applying the principle of uti possidetis juris, is not entirely convincing. Similarly,
the Tribunal’s interpretation and application of Article 15 UNCLOS in delimiting
the territorial sea boundary in the Gulf of Trieste has attracted some criticism from
commentators.
27
Secondly, the distinction in Article 4 reflects, among other things, the difficulties
encountered by the Parties in their previous bilateral attempts to resolve what
seemed to be the most controversial issue at stake, namely Slovenia’s claim to have
direct territorial access to the high seas. By requiring the Arbitral Tribunal to rely on
“equity and the principle of good neighbourly relations” in order to “achieve a fair
and just result” with respect to that issue, the two States arguably imparted the necessary flexibility to the arbitration process, in view of the final settlement of the
dispute between them. This is confirmed by the fact that the Tribunal had to apply
this broader set of rules and principles also in determining the regime for the use of
all “the relevant maritime areas”—i.e., not only the “junction” area, but also the
other, previously delimited, maritime areas between the two countries, and especially those within the Bay of Piran (which, in the aftermath of the adoption of the
Final Award, seem to have become the source of renewed tension between the two
States).
The Final Award of 29 June 2017 clearly distinguishes between, on the one hand,
determinations in respect of the Piran Bay and, on the other hand, determinations in
respect of other maritime areas. The Arbitral Tribunal proceeded first by: defining
27 Vidas (2018), pp. 58–61, for instance, notes that the Final Award of 29 June 2017 “fully confirms - and further aggravates - the reasons for concern expressed here about some recent trends in
case law on the territorial sea delimitation”.
The Law of Maritime Delimitation in the Croatia/Slovenia Final Award