Wellington, March 15 NZPA - The arrest of Auckland anti-whaling activist Pete Bethune has drawn a mixed response in Japan, with some officials saying he should have been deported.

Mr Bethune, 44, illegally boarded the Japanese whaling ship No 2 Shonan Maru in the Antarctic Ocean on February 15, to protest the sinking of his trimaran Ady Gil during a confrontation with another Japanese whaling ship on January 6.

He was promptly taken into custody for trespassing, then arrested when the ship docked in Tokyo last week. Authorities have still to decide what to do about him.

Prime Minister John Key has said the Government here can not intervene in Japan's legal process.

"He's going to be charged across a range of different sort of breaches of the law, potentially," Mr Key said. "We can't actually interfere in the Japanese legal process."

Mr Bethune was trying to make a citizen's arrest of the Shonan Maru captain for damaging the Ady Gil -- the former Earthrace vessel -- when he clambered aboard the ship from a jet ski.

The Japanese Daily Yomiuri reported that while it was possible to crack down on acts of piracy such as robbery based on the UN Convention of the Law of the Sea and anti-piracy law, "the Foreign Ministry does not regard Sea Shepherd protest activities as acts of piracy".

It said the coastguard now wanted him charged with injuring Japanese sailors by throwing corrosive butyric acid at them.

Members of the Sea Shepherd Conservation Society have for several year bottled butyric acid and thrown it onto whaling ships -- where the rancid butter-like smell spoils any whale meat it splashes.

The newspaper said it was clear the society aimed to protest against whaling in court and Japanese authorities handling the issue "have been carefully preparing for the case, so as not to give activists ammunition for protests".

"Some officials have argued that Bethune should have been deported."

The Asahi Shumbun newspaper reported on its English-language website that Hajime Ishikawa, an official at the survey division of the Institute of Cetacean Research in Tokyo, which oversees Japan's "research" whaling, said the arrest was long overdue.

"There was a sense of helplessness with the violence continuing every year and nothing being done about it," Mr Ishikawa said. "Having even one person face justice is meaningful."

But Masayuki Komatsu, a former bureaucrat at the Fisheries Agency, told Asahi Shimbun that the arrest of Mr Bethune served only the cause of the anti-whaling activists.

"With the commotion caused by bringing him to Japan, Sea Shepherd has accomplished about 80 percent of its goal to appeal its activities to the world," Mr Komatsu said. "If it were necessary to arrest him, there was the option of asking another country or organisation to do it."

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