Are they whaling in Australian waters as recognized by treaty? If they are, this could create some tensions. GreenPeace has used these tactics for years, but the whalers have gotten pretty good at dealing with them.
And that's precisely why diplomats and, if necessary, standing armed forces exist....to enforce treaties among other things.
Greenpeace is not an organization that is empowered by Australia or any other Government to enforce it's laws, and when it takes it upon itself to engage in terrorist actions such as this, while pathetically attempting to wrap itself in the cloak of a 'law enforcement agency' then it's stinky and unkempt hippie membership need to expect to be treated as the terrorists that they are.
GreenPeace has used these tactics for years, but the whalers have gotten pretty good at dealing with them.
And in this case I'm hoping that the Japanese Captain will get a stern lecture from the appropriate Japanese governing bodies, as his ship could very easily have wound up as another USS Cole incident. The world has changed since the 1970's, and limp-wristed acceptance of environmental terrorism can no longer be tolerated.