The UN's top court on Monday ordered Japan to end its annual Antarctic whale hunt, saying in a landmark ruling that the program was a commercial activity disguised as science.
"Japan shall revoke any existant authorization, permit or license granted in relation to JARPA II (research program) and refrain from granting any further permits," said the International Court of Justice's Judge Peter Tomka.
Agreeing with Australia, which in 2010 hauled Japan before the Hague-based ICJ in a bid to end whale hunting in the Southern Ocean, Tomka said that "special permissions granted by Japan are not for purposes of scientific research."
"The evidence does not establish that the program's design and implementation are reasonable in relation to its stated (scientific) objectives," Tomka said.
While Norway and Iceland have commercial whaling programs in spite of a 1986 International Whaling Commission (IWC) moratorium, Japan insisted its program was scientific, while admitting that the resulting meat ended up on plates back home.
Tokyo was accused of exploiting a legal loophole in the 1986 ban on commercial whaling that allowed the practice to collect scientific data.
Conservation groups voiced happiness at the ruling, which Japan said it would respect despite "deep disappointment".
"As a state that respects the rule of law... and as a responsible member of the global community, Japan will abide by the decision of the court," chief negotiator Koji Tsuruoka told reporters outside the United Nations' top court.
Australia's lawyer Bill Campbell said he welcomed the decision and repeated his hope that it would not affect relations between the two countries.
"The decision of the court today, important as it is, has given us the opportunity to draw a line under the legal dispute and move on," Campbell said.
Australia said that since 1988 Japan has slaughtered more than 10,000 whales under the program, putting the Asian nation in breach of international conventions and its obligation to preserve marine mammals and their environment.
Pete Bethune, a former activist with militant conservation group Sea Shepherd who spent five months in a Japanese prison for his protests, broke down after the verdict.
"Today is a great day for justice," he told journalists at the court.
"This decision sends a clear message to governments around the world that the exploitation of animals will no longer be tolerated and animals must be protected at the highest level," said Claire Bass, head of wildlife campaigns at the World Society for the Protection of Animals.
"All eyes are now on Japan to respect this decision," she said.
The court ruled overwhelmingly in favor of Australia in the case, which the country launched in 2010.
Clare Perry of the Environmental Investigation Agency said the ruling "lays to rest, once and for all, the grim travesty of Japan's so-called 'scientific' whaling."
"Next, the world needs to focus its attention on Japan's whaling in the North Pacific, where it continues to issue permits to kill up to 500 whales annually in hunts using the same 'scientific' clause that has now been condemned beyond dispute by the international court."
While Japan said its research program was aimed at studying the viability of whale hunting, the ICJ found that it had failed to examine ways of doing such research without killing whales, or at least while killing fewer whales.
Japan has consistently defended the practice of eating whale meat as a culinary tradition and vowed it would "never stop whaling."
In April last year it announced its whaling haul from the Southern Ocean was at a record low because of "unforgivable sabotage" by Sea Shepherd activists.
Sea Shepherd had called the ICJ case make-or-break for whales in the Southern Ocean.
Established in 1945 to rule in disputes between countries, the ICJ is the UN's highest judicial body and the only one of five principal UN bodies not located in New York.