I will be surprised if this actually happens, but it is telling that the Australian foreign minister even brought it up:
AUSTRALIA’S Foreign Minister Stephen Smith has told Tokyo that federal police are "considering" prosecuting members of the militant anti-whaling Sea Shepherd Conservation Society when its vessel docks in Melbourne today.
Mr Smith discussed the possibility in a meeting with Japan’s Foreign Minister, Masahiko Komura, who has repeatedly urged Australia to charge crew from the ship, the Steve Irwin, who boarded a Japanese whaling vessel in the Southern Ocean last month.
Two Sea Shepherd crew members — an Australian, Benjamin Potts, and a Briton, Giles Lane — were held by Japanese whalers after climbing aboard the Yushin Maru No. 2 in mid-January without permission.
They were later turned over to an Australian Customs ship. [The Age]
You can read about the Sea Shepherd boarding of the Japanese ship and subsequent Australian media cover up here.
I have no problem with people protesting, but when they ram ships, throw acid bombs, entangle nets into ships’ propellers, and now even boarding vessels it goes over the line of protesting and into the realm of criminal activity that these people should be held accountable for.