Arbitration — Stay of procceedings — Jurisdiction of domestic courts Arbitration clause in contract between government and company Reference of matter to International Centre for the Settlement of Investment Disputes — Whether domestic proceedings relate to matter over which arbitration proceedings brought — Agreement containing favourable rights of purchase — Dispute over effect of subsequently enacted legislation Whether dispute arising under the terms of the agreement — Whether Court having residual discretion to take jurisdiction over matter — Whether government bound by agreement to international arbitration — Arbitration (International Investment Disputes) Act, 1979— The law of New Zealand