Fugitive eco-warrior Paul Watson has vowed to continue campaigning "undaunted" by legal threats, after landing back in the United States following 15 months on the run at sea.
The Canadian said Thursday he was heading for Seattle after arriving in Los Angeles earlier this week, to defend himself from legal action there.
"I have returned to the United States," he said in a statement on his Facebook page, adding that an Interpol "Red Notice" from Costa Rica "has been dropped".
Watson is wanted by Interpol after skipping bail in Germany in July last year, where he was arrested on Costa Rican charges relating to a high-seas confrontation over shark finning in 2002.
The 62-year-old arrived in Los Angeles on Monday.
"Captain Paul was not arrested upon entry in the the United States and is there to testify in defense of his name in the contempt of court proceedings against himself from the illegal whale poachers from Japan," Jeff Hansen, the Australia director of conservation activist group Sea Shepherd said.
Watson said he would challenge a Red Notice requested by Japan in the United States, adding that he was "heading to Seattle to defend Sea Shepherd and myself from the... civil suit launched by the Japanese whalers.
"We carry on with our efforts to save the oceans, undeterred and undaunted."
In Tokyo, Japanese officials said they were trying to confirm reports.
"The government has no more information at the moment other than Japan continues to request the captain's arrest," Deputy Chief Cabinet Secretary Katsunobu Kato said.
Watson decided to disembark to testify in a court case due to take place next week in Seattle over his marine conservation organisation's actions in Antarctica against Japanese whalers.
His Facebook page was immediately flooded with thousands of "likes" and hundreds of comments.
"So glad you are back! Please keep up the fight for our oceans! You are a modern day hero!" wrote Melissa Smith-Janicek, while Sebastian Phillips wrote: "This world needs more like you... stay strong, outlast, change the world!"
Watson was arrested in May last year in Frankfurt on a warrant from Costa Rica, where he is wanted on charges stemming from a high-seas confrontation over shark finning in 2002.
He was released on bail after paying a fine, and was ordered to appear before police twice a day. But he skipped bail on July 22, 2012 and fled Germany.
The following month, France-based Interpol issued an international request for his arrest.
The organisation does not have the power to issue international arrest warrants but can ask member countries to make arrests based on foreign warrants through a Red Notice.
Watson, known to his supporters as "The Captain," had been on the run at sea since then, and even participated in a new campaign against Japanese whalers in Antarctica last winter.
And when an anti-whaling fleet he had been on docked in Australia in March, he made no appearance on the ground, but the country's attorney general hinted he would not be detained if he came to shore.
Japanese authorities describe methods used by Sea Shepherd against whaling ships -- for example blocking the boats' propellers -- as "terrorist".
A US appeals court in February labelled the Sea Shepherd group as pirates, overturning a lower court's ruling against Japanese whalers. Sea Shepherd were ordered to maintain a distance of 500 metres (yards) from Japanese whaling ships.
Japan's Institute of Cetacean Research and others are pursuing legal action in the United States, seeking an injunction against their activities on the high seas.
Japan claims it conducts vital scientific research using a loophole in an international whaling ban agreed at the International Whaling Commission (IWC), but makes no secret that the mammals ultimately end up on dinner plates.
Japan defends whaling as a tradition and accuses Western critics of disrespecting its culture. Norway and Iceland are the only nations that hunt whales in open defiance of a 1986 IWC moratorium on commercial whaling.