Who Decides? The ECJ's Judgment on Jurisdiction in the MOX Plant Dispute: Failure of a Member State to fulfil obligations--United Nations Convention on the Law of the Sea--Part XII--Protection and preservation of the marine environment--Dispute-settlement system provided for under that convention--Arbitration proceedings initiated on the basis of that system by Ireland against the United Kingdom--Dispute relating to the MOX plant at Sellafield (United Kingdom)--Irish Sea--Articles 292 EC and 193 EA--Undertaking not to submit a dispute relating to the interpretation or application of the Treaty to a method of settlement other than those provided for by the Treaty--Mixed agreement--Community competence--Articles 10 EC and 192 EA - Duty of coo