211
its commitments in the course of over 40 years since 1965,
85
the Tribunal found that
all the requirements for the estoppel principle to be applied had been met: the representations were clear and consistent; the relevant statements were made by agents
unequivocally authorised to speak for the United Kingdom, namely the Prime
Minister and the Foreign Secretary; the reliance of Mauritius on the United
Kingdom’s repeated representations was detrimental in that Mauritius forewent
opportunities, including the chance of pressing its sovereignty claim and accepting
the United Kingdom’s offer to stipulate a treaty formalising the undertaking to eventually return the islands; Mauritius’ reliance on the United Kingdom’s commitments
was legitimate in consideration of the consistent repetition and the terms thereof.
86
The described approach of the Tribunal in determining the source of Mauritius’
rights proves ambiguous in that it would have been unnecessary for the Tribunal to
ascertain the “legal significance” of the United Kingdom’s repetition of its undertakings, once the binding nature of the 1965 United Kingdom’s commitments had
been found in their “transformation” into an international agreement. Such “transformation” of the Lancaster House Undertakings would alone have allowed the
application of Articles 2(3) and 56(3) UNCLOS.
It is here argued that the relevance of the Lancaster House Undertakings to the
land sovereignty dispute drove the Tribunal to be cautious about a clear application
thereof and, accordingly, to find the source of Mauritius’ rights also in the United
Kingdom’s repetition of its commitments. Whereas the commitments that the
United Kingdom has repeated since 1965 specifically concern Mauritius’ fishing
rights and the return of the islands and benefit of any minerals or oil discovered in
or near the Archipelago to Mauritius, the ‘original’ Lancaster House Undertakings
are mainly about the detachment of the Chagos Archipelago and thus have a bearing
on the sovereignty dispute: it is on the basis of those Undertakings that the Chagos
Archipelago was detached from Mauritius to form the BIOT.
87
Indeed, the Tribunal
was fully aware of the importance of the Lancaster House Undertakings for the
sovereignty dispute. As mentioned before, it conceded that the determination of the
legal effect of the Lancaster House Undertakings was a key factor not only for
Mauritius’ fourth submission, but also for the Parties’ submissions on sovereignty
and the identity of the coastal State.
88
It is true that, in ascertaining a breach of Articles 2(3) and 56(2) UNCLOS, the
Tribunal eventually referred to “Mauritius’ rights and interests arising out of the
Lancaster House Undertakings”.
89
Nevertheless, in generally concluding on the
them maintaining that the Mauritian colonial government had a limited degree of international
legal personality.
85 Chagos Marine Protected Area Arbitration, paras 429–433.
86 Ibidem, paras 434–447.
87 In this connection, see Yee (2018), pp. 636–637, arguing that the settlement of the land sovereignty dispute essentially depends on the determination of the validity of the Lancaster House
Undertakings.
88 Chagos Marine Protected Area Arbitration, paras 418–419.
89 Ibidem, para. 534. Similarly, in para. 535, the reference may be read to “Mauritius’ rights arising
from the Lancaster House Undertakings”.
The Interpretation of the United Nations Convention on the Law of the Sea…
its commitments in the course of over 40 years since 1965,
85
the Tribunal found that
all the requirements for the estoppel principle to be applied had been met: the representations were clear and consistent; the relevant statements were made by agents
unequivocally authorised to speak for the United Kingdom, namely the Prime
Minister and the Foreign Secretary; the reliance of Mauritius on the United
Kingdom’s repeated representations was detrimental in that Mauritius forewent
opportunities, including the chance of pressing its sovereignty claim and accepting
the United Kingdom’s offer to stipulate a treaty formalising the undertaking to eventually return the islands; Mauritius’ reliance on the United Kingdom’s commitments
was legitimate in consideration of the consistent repetition and the terms thereof.
86
The described approach of the Tribunal in determining the source of Mauritius’
rights proves ambiguous in that it would have been unnecessary for the Tribunal to
ascertain the “legal significance” of the United Kingdom’s repetition of its undertakings, once the binding nature of the 1965 United Kingdom’s commitments had
been found in their “transformation” into an international agreement. Such “transformation” of the Lancaster House Undertakings would alone have allowed the
application of Articles 2(3) and 56(3) UNCLOS.
It is here argued that the relevance of the Lancaster House Undertakings to the
land sovereignty dispute drove the Tribunal to be cautious about a clear application
thereof and, accordingly, to find the source of Mauritius’ rights also in the United
Kingdom’s repetition of its commitments. Whereas the commitments that the
United Kingdom has repeated since 1965 specifically concern Mauritius’ fishing
rights and the return of the islands and benefit of any minerals or oil discovered in
or near the Archipelago to Mauritius, the ‘original’ Lancaster House Undertakings
are mainly about the detachment of the Chagos Archipelago and thus have a bearing
on the sovereignty dispute: it is on the basis of those Undertakings that the Chagos
Archipelago was detached from Mauritius to form the BIOT.
87
Indeed, the Tribunal
was fully aware of the importance of the Lancaster House Undertakings for the
sovereignty dispute. As mentioned before, it conceded that the determination of the
legal effect of the Lancaster House Undertakings was a key factor not only for
Mauritius’ fourth submission, but also for the Parties’ submissions on sovereignty
and the identity of the coastal State.
88
It is true that, in ascertaining a breach of Articles 2(3) and 56(2) UNCLOS, the
Tribunal eventually referred to “Mauritius’ rights and interests arising out of the
Lancaster House Undertakings”.
89
Nevertheless, in generally concluding on the
them maintaining that the Mauritian colonial government had a limited degree of international
legal personality.
85 Chagos Marine Protected Area Arbitration, paras 429–433.
86 Ibidem, paras 434–447.
87 In this connection, see Yee (2018), pp. 636–637, arguing that the settlement of the land sovereignty dispute essentially depends on the determination of the validity of the Lancaster House
Undertakings.
88 Chagos Marine Protected Area Arbitration, paras 418–419.
89 Ibidem, para. 534. Similarly, in para. 535, the reference may be read to “Mauritius’ rights arising
from the Lancaster House Undertakings”.
The Interpretation of the United Nations Convention on the Law of the Sea…