The International Court of Justice's (ICJ) decision in The Hague comes after years of animosity between Australia and Japan over the legality and morality of whaling.

Until last year the debate played itself out in the structured but ultimately toothless confines of the International Whaling Commission (IWC) and the highly emotive court of public opinion.

Because today's ruling comes from the ICJ and not the voluntary IWC, it is the first legally binding decision for the two countries and New Zealand, which made submissions.

Japan has said it respects international law and has promised to abide by The Hague's decision.

In the event that it decides to defy the court's ruling, there is a theoretical possibility that the United Nations Security Council could step in as enforcer, but international law experts say this is almost inconceivable.

With fierce national pride and centuries of tradition, it is unclear whether the ICJ decision will mean an end to Japanese whaling.

What is clear is that a precedent has been set: Japan's scientific whaling program has been judged illegal in the eyes of the law.

International law expert Steven Freeland says Japan now finds itself in a difficult position because the ICJ has taken away its justification for whaling.

He says the ruling will do little to persuade a Japanese public that is largely in favour of a centuries-old whaling tradition.

"Japan of course in abiding with [the decision] would have to stop its program because it's in breach of the convention," he said.

"What options would Japan have then? It really depends on how Japan would view the overall context of whaling because ... there is always the option to withdraw from the regime altogether by giving six months notice.

"At an extreme end if Japan felt very strongly about continuing some form of whaling and yet it had to abide by this position, it could take that extreme step."

Mr Freeland says he does not expect this decision to provide much resolution for the vexed issue of whaling.

"I think after this decision ... countries have to get together with cool heads and still need to talk and that's always been the issue," he said.

"Discussions over the past years have been on an all-or-nothing basis where Australia says 'no whaling whatsoever' and Japan says they reserve the right because it's part of their culture and [they're] allowed to do it anyway under the scientific whaling."

Mr Freeland says legal avenues remain for Japan which may permit whaling.

Japanese whaling restrictions: a brief history

Signatories at the 1947 signing of the International Convention For The Regulation Of Whaling in Washington DC. ( Supplied: IWC )