398
of incidental jurisdiction would be barred. There are indeed cases that seem to support this reading of the “necessity” requirement.
71
For example, in the South China
Sea arbitration, the Annex VII Tribunal held that it “might consider that the
Philippines’ Submissions could be understood to relate to sovereignty [such as to
exclude the jurisdiction] if it were convinced that either (a) the resolution of the
Philippines’ claims would require the Tribunal to first render a decision on sovereignty, either expressly or implicitly; or (b) the actual objective of the Philippines’
claims was to advance its position in the Parties’ dispute over sovereignty”.
72
Nevertheless, it should be recalled that “necessity” or the concept of “prerequisite
determination” have never been taken alone as factors sufficient to characterize a
dispute or to identify the real issue in the case. While this factor plays a crucial role
for the application of the doctrine indispensable parties, which relates to the scope
of the jurisdiction ratione personae, in the context of the assessment of their jurisdiction ratione materiae, as seen, international tribunals usually consider a number
of other factors.
73
Finally, when it comes to the determination of the scope of the incidental jurisdiction over external issues, the requirement of necessity, together with the assessment of an “incidental connection” between the relevant issues, must be combined
with a third factor referred to in Chagos, that of the “minor” character of the external issue. In other words, while “necessity” may turn out to be decisive in a given
case in order to exclude the jurisdiction ratione materiae, it can still be pivotal to
trigger the incidental jurisdiction, without prejudice to the principal jurisdiction,
where the external issue is a “minor” issue. As seen, the Chagos Tribunal added this
latter requirement when specifically referring to disputes that “necessarily involve
the concurrent consideration of any unsettled dispute concerning sovereignty”
(mixed disputes). Yet, it is not entirely clear whether this last requirement refers to
the geographical or physical character of the maritime feature concerned,
74
or simply to the relative secondary or subordinate character of the territorial sovereignty
issue, which would imply that the minor character is nothing but a specification of
the incidental or ancillary requirement.
75
This second view would render this
71 Ibidem, pp. 128–130. See also Buga (2012), pp. 81–83.
72 South China Sea Arbitration, para. 153 (emphasis added).
73 That is the reason why the doctrine of indispensable parties and the alleged doctrine of indispensable issues (as drawn by Tzeng (2017)) cannot be entirely juxtaposed. Salles (2014), pp. 121–122,
makes the point clear by arguing that: “[a] caveat to the proposition that incidental jurisdiction
extends beyond principal jurisdiction is this: when the very subject matter of the required decision
on issues of fact and law that would otherwise be permitted in the exercise of incidental jurisdiction
entangles the legal position of a state non-party to the proceedings, the tribunal cannot exercise
inherent powers […] after all, third parties that have not delegated principal jurisdiction cannot
have implicitly delegated incidental jurisdiction. In sum, whereas necessity justifies the exercise of
incidental jurisdiction ratione materiae, the limitations to incidental jurisdiction ratione personae
are stricter”.
74 See Tanaka (2016), p. 319, who maintains that low-tide elevations would meet the criterion of the
“minor issue”.
75 In this respect, it is worth noting that the same concept of incidental jurisdiction has been polemically challenged with arguments relating to geography of the territorial sovereignty issue within
L. Marotti
of incidental jurisdiction would be barred. There are indeed cases that seem to support this reading of the “necessity” requirement.
71
For example, in the South China
Sea arbitration, the Annex VII Tribunal held that it “might consider that the
Philippines’ Submissions could be understood to relate to sovereignty [such as to
exclude the jurisdiction] if it were convinced that either (a) the resolution of the
Philippines’ claims would require the Tribunal to first render a decision on sovereignty, either expressly or implicitly; or (b) the actual objective of the Philippines’
claims was to advance its position in the Parties’ dispute over sovereignty”.
72
Nevertheless, it should be recalled that “necessity” or the concept of “prerequisite
determination” have never been taken alone as factors sufficient to characterize a
dispute or to identify the real issue in the case. While this factor plays a crucial role
for the application of the doctrine indispensable parties, which relates to the scope
of the jurisdiction ratione personae, in the context of the assessment of their jurisdiction ratione materiae, as seen, international tribunals usually consider a number
of other factors.
73
Finally, when it comes to the determination of the scope of the incidental jurisdiction over external issues, the requirement of necessity, together with the assessment of an “incidental connection” between the relevant issues, must be combined
with a third factor referred to in Chagos, that of the “minor” character of the external issue. In other words, while “necessity” may turn out to be decisive in a given
case in order to exclude the jurisdiction ratione materiae, it can still be pivotal to
trigger the incidental jurisdiction, without prejudice to the principal jurisdiction,
where the external issue is a “minor” issue. As seen, the Chagos Tribunal added this
latter requirement when specifically referring to disputes that “necessarily involve
the concurrent consideration of any unsettled dispute concerning sovereignty”
(mixed disputes). Yet, it is not entirely clear whether this last requirement refers to
the geographical or physical character of the maritime feature concerned,
74
or simply to the relative secondary or subordinate character of the territorial sovereignty
issue, which would imply that the minor character is nothing but a specification of
the incidental or ancillary requirement.
75
This second view would render this
71 Ibidem, pp. 128–130. See also Buga (2012), pp. 81–83.
72 South China Sea Arbitration, para. 153 (emphasis added).
73 That is the reason why the doctrine of indispensable parties and the alleged doctrine of indispensable issues (as drawn by Tzeng (2017)) cannot be entirely juxtaposed. Salles (2014), pp. 121–122,
makes the point clear by arguing that: “[a] caveat to the proposition that incidental jurisdiction
extends beyond principal jurisdiction is this: when the very subject matter of the required decision
on issues of fact and law that would otherwise be permitted in the exercise of incidental jurisdiction
entangles the legal position of a state non-party to the proceedings, the tribunal cannot exercise
inherent powers […] after all, third parties that have not delegated principal jurisdiction cannot
have implicitly delegated incidental jurisdiction. In sum, whereas necessity justifies the exercise of
incidental jurisdiction ratione materiae, the limitations to incidental jurisdiction ratione personae
are stricter”.
74 See Tanaka (2016), p. 319, who maintains that low-tide elevations would meet the criterion of the
“minor issue”.
75 In this respect, it is worth noting that the same concept of incidental jurisdiction has been polemically challenged with arguments relating to geography of the territorial sovereignty issue within
L. Marotti