On March 18, 2015, the Permanent Court of Arbitration (PCA) issued its award [3]  in the matter of the Chagos Marine Protected Area Arbitration (Mauritius v. United Kingdom), unanimously finding the United Kingdom’s establishment of a marine protected area (MPA) around the Chagos Archipelago contravened its obligations under the Convention on the Law of the Sea [4].  According to the press release [3], Mauritius commenced the arbitration before the PCA in 2010 after the United Kingdom declared an MPA in the waters surrounding the Chagos Archipelago. The Archipelago has been administered by the United Kingdom as part of the British Indian Ocean Territory since 1965 and, before then, as a dependency of its then-colony, Mauritius. Mauritius submitted, among other claims, that the United Kingdom was “not entitled to declare an MPA or other maritime zones because it is not the ‘coastal State’ for the purposes of the Convention,” nor could it, given its 1965 commitments to Mauritius, “unilaterally [] declare an MPA or other maritime zones because Mauritius has rights as a ‘coastal State.’” The PCA interpreted these claims as rooted in a dispute over the sovereignty of the Archipelago and noted that it did not have jurisdiction over that issue. However, it held that “in declaring the MPA, the United Kingdom failed to give due regard to [Mauritius’s] rights and declared that the United Kingdom had breached its obligations under the Convention.”