"I can't accept this verdict," said Yutaka Sunaga, who runs the Kujiraya Taiju whale meat restaurant in Chiba, near Tokyo. "However you look at it, it's unreasonable to say we can't catch them. If you say you feel sorry for the whales, it's the same when you eat other types of animals."

Watch: Japan says will honour ICJ whaling decision

The International Court of Justice in The Hague said Japan's open-ended whale hunting programme in the Southern Ocean must cease. Japan would be barred from restarting whaling unless it could prove the hunt was for scientific purposes and could not be done by non-lethal means, the court ruling said. Australia, which brought the lawsuit against Japan, said the research was a "ruse" to skirt the prohibition against commercial killing.

The world court's decision leaves Japan with a choice: end whaling outright, despite past claims that it would never abandon such a deep-seated cultural practice, or redesign its programme to make it a scientific endeavour after all. Japan has all but ruled out joining Norway and Iceland in flouting the international consensus against commercial whaling.

Japanese government officials said they were disappointed and would "abide by the judgment of the court as a state that places great importance on the international legal order", Koji Tsuruoka, a foreign ministry official who is the government's representative in the case, said in an e-mailed statement. Chief Cabinet Secretary Yoshihide Suga said in a statement that Japan would consider how to proceed after examining the verdict.

The court said Japan's current research programme, known as JARPA II, "can broadly be characterised as scientific research, though the evidence does not establish that the programme's design and implementation are reasonable in relation to achieving its stated objectives. The Court concludes that the special permits granted by Japan for the killing, taking and treating of whales in connection with JARPA II are not for purposes of scientific research."

While the decision ends JARPA II, it did not automatically mean Japan would cease all whaling, said Don Rothwell, a professor and head of the Australian National University's College of Law in Canberra. With the whaling season ended, Japan might decide to present a new programme to the International Whaling Commission when it meets in September that conforms to the court's interpretation of Article VIII of the International Convention for the Regulation of Whaling, he said.

"The court has not struck out Article VIII of the whaling convention, it's just provided some guidance as to how it can be interpreted," Rothwell said. "There would be nothing stopping Japan undertaking a new whaling programme that doesn't have the objectionable parameters of JARPA II but conforms to the broad parameters of the court judgment."

Japan has been the most active of the traditional whaling nations to use the scientific research provision of the international treaty on whaling to continue killing the marine mammals and retain a market for their meat. Japan has taken more than 13,000 whales since the start of the moratorium, saying its research can only be conducted by lethal means.

During the trial last June, Japan presented only two scientific reports based on the harpooning of 3,600 minke whales and a handful of fin whales during a seven-year period.

"It was no coincidence that Japan only started to issue special permits authorising large-scale so-called 'scientific whaling' immediately after the moratorium on whaling for commercial purposes came into effect," Australia said in its complaint. The permits "were but a ruse to enable the continuation of whaling by Japan".

"The decision seems to dispose of the issue of whaling," Australian Attorney-General George Brandis told reporters in Perth. "Both Australia and Japan have stated on a number of occasions that both countries would accept and respect the decision of the court."

Japan killed almost 95 per cent of the 14,410 whales hunted for research since the moratorium, Australia said in its suit. In the 34 years prior to the moratorium taking effect, a total of 2,100 whales were killed for research, it said.

"The research take of whales is not a violation or an abuse of a loophole in the international convention," Japan's Ministry of Foreign Affairs said on its website before the decision. "Quite the contrary, this is a legitimate right of the contracting party" under the convention.

Consumption of whale meat has fallen sharply in Japan since the mid-20th century, leaving the Japanese government with huge surpluses of the once-popular protein source. Greenpeace estimates that Tokyo has had to subsidise the whale hunt at a cost of about US$10 million a year and is forced to freeze and store thousands of tonnes of unsold meat.

In January, the US ambassador to Japan, Caroline Kennedy, criticised the killing of bottlenose dolphins by Japan in an annual hunt off the coastal town of Taiji. "Deeply concerned by inhumaneness of drive-hunt dolphin killing," Kennedy said in a post on Twitter on January 18, referring to the method by which the animals are herded into a cove before being killed.

With the advent of modern whaling techniques, such as explosive-tipped harpoons and factory ships, whaling nations were still killing tens of thousands of the animals a year in the mid-20th century, pushing many species near extinction. Despite the moratorium, some species have struggled to recover. Unlike fish that can lay hundreds of eggs, whales are mammals that tend to birth a single calf every two to four years, with gestation periods lasting as long as 18 months.

Growing public awareness of the killing of whales helped fuel the modern environmental movement, with groups such as Greenpeace, the World Wildlife Fund and the Sea Shepherd Conservation Society gaining international recognition. The campaign to "Save the Whales" led to calls for a ban on whaling that gave rise to the passage of the moratorium by a majority of the nations of the International Whaling Commission in 1982 that was started four years later.

Conservation groups say that Japan has championed scientific whaling to keep its industry alive and maintain a culture of eating whale meat until it can work with other nations to weaken or overturn the moratorium. Greenpeace estimates the Japanese government spends about ¥6 billion yen (HK$451 million) annually on its catch, recovering about ¥5 billion from the sale of meat. Falling demand in Japan has left the government with stockpiles of frozen meat.

Greenpeace Japan's Tokyo-based executive director, Junichi Sato, said the Japanese government should stop the whale hunt near Antarctica "and not seek any loopholes".

Japan says it "strongly supports" the international protection of endangered whale species such as the blue whale, while criticising the moratorium for also covering more abundant species that may not have been threatened, such as the minke whales it hunts in waters near Antarctica.

While the court did not say how many whales could be taken for scientific research, it did comment on "the disconnect between the number of whales that were taken and the objectives of the research programme", the ANU's Rothwell said. That might discourage Japan from relaunching a smaller whaling programme as its economies of scale might not be viable, he said.

The UN court's ruling was cheered by environmentalists and animal rights advocates worldwide, even though the halt to Japan's Antarctic operations might be temporary.

The court left open the possibility of Japan revising its scientific whaling programme to conform with the whaling commission ban's exclusions criteria.