A trans-Tasman bid to stop Japan whaling in the Southern Ocean will begin before the International Court of Justice on Tuesday.
Australia and New Zealand are taking the case to the Hague in a hearing set down for three weeks.
Australia is leading the legal action, claiming that Japan is breaching international law by commercial whaling under the guise of scientific research.
Japan is disputing the jurisdiction of the court to hear the case.
New Zealand is considered an intervener in the case, which means it backs the Australian argument and is bound by the court's decision but does not bear the same responsibilities or costs. It will also be allowed to make a brief statement to the court in July.
The court usually takes six to nine months to make its rulings.