The International Court of Justice (ICJ) has ordered Japan to halt its controversial Antarctic whaling program.
The Court in The Hague, Netherlands, ruled that Tokyo's Jarpa II whaling program was not for scientific purposes.
"In light of the fact the Jarpa II has been going on since 2005, and has involved the killing of about 3,600 minke whales, the scientific output to date appears limited," said presiding judge Peter Tomka.
"Japan shall revoke any existent authorisation, permit or licence granted in relation to Jarpa II and refrain from granting any further permits in pursuance to the program."
The ICJ 16-judge panel ruled in favour of Australia, which filed a lawsuit against Japan demanding the end of whaling in the icy Southern Ocean in 2010.
Australia claimed that Jarpa II served commercial rather than scientific purposes.
The ICJ said that: "taken as a whole, the Court considers that Jarpa II involves activities that can broadly be characterised as scientific research, but that 'the evidence does not establish that the programme's design and implementation are reasonable in relation to achieving its stated objectives'."
Australia said that under the Jarpa II program and its predecessor, Jarpa, Japan had slaughtered more than 10,000 whales since 1988.
The Court said its decision was partially based on the fact that there was no evidence Tokyo had conducted any studies of the feasibility or practicality of alternative non-lethal research methods.
Before the ruling was pronounced Japan said it would abide by it.
The verdict was celebrated by conservationists. Ocean conservation and protection group Sea Shepherd tweeted:
Australia's green senator Christine Milne tweeted: