International tribunals — Provisional measures of protection — International Tribunal for the Law of the Sea — Applicable law — United Nations Convention on the Law of the Sea, 1982 (“UNCLOS”) — Ireland and United Kingdom both States Parties to UNCLOS — Request by Ireland for the establishment of an Annex VII Arbitral Tribunal — Request by Ireland for the indication of provisional measures under UNCLOS Article 290(5) pending constitution of Annex VII Arbitral Tribunal

Sea — Marine environment — UNCLOS — Environmental effects of the MOX nuclear plant and of international movements of radioactive materials — Obligation to cooperate in taking measures to protect and preserve the Irish Sea — Precautionary principle

Treaties — Interpretation and application — UNCLOS — Compulsory procedures for settlement of disputes — UNCLOS Articles 281 and 282 — Whether applicable — Relationship between Article 282 and compulsory dispute settlement procedures under other treaties — Convention for the Protection of the Marine Environment of the North-East Atlantic, 1992 (“OSPAR Convention”) — Treaty Establishing the European Atomic Energy Community, 1957 (“Euratom Treaty”) — Treaty Establishing the European Community, 1957 (“EC Treaty”) — Commencement of dispute settlement procedures under the OSPAR Convention not precluding resort to compulsory dispute settlement under UNCLOS — Provisions of other treaties not relevant to dispute concerning the interpretation and application of UNCLOS — UNCLOS Article 282 not applicable

Sea — UNCLOS — Article 290(5) — Conditions to be satisfied for prescription of provisional measures under Article 290(5) — Whether prima facie basis for the jurisdiction of the Annex VII Arbitral Tribunal — Whether urgent necessity for prescription of provisional measures pending the constitution of Annex VII Arbitral Tribunal — Irreparable prejudice — Serious harm to the marine environment — Requirement of urgency not satisfied — Power of International Tribunal to prescribe provisional measures different in whole or in part to those requested