Fugitive eco-activist Paul Watson is due in a US court this week for his latest legal battle -- but, after 15 months on the run, he says he is happy to leave the high seas clashes to friends in Australia.

The Canadian-born Sea Shepherd founder arrived in California last week more than a year after fleeing arrest in Germany, spending most of the intervening time at sea in the South Pacific and Southern Ocean.

In an interview with AFP the 62-year-old said he expects to take the stand in a Seattle courtroom on Wednesday, to defend himself against accusations of piracy brought by Japanese whalers.

But the white-bearded activist says he does not expect a judge to lift an injunction on him joining Sea Shepherd boats due to leave Australia within weeks for an annual campaign against Japanese whaling vessels.

"I don't believe that the injunction will be lifted, so I don't plan on going on the campaign," said Watson, who is banned from participating along with the Oregon-based Sea Shepherd Conservation Society (SSCS).

"But I'm not particularly concerned about it because Sea Shepherd Australia is quite capable, as they've proven ... to carry out the campaign," he added.

The Australian arm of the environmental group is ready to set sail again on December 1 to disrupt the Japanese whalers, said Watson, known to his loyal supporters as "The Captain."

Sea Shepherd, founded by former Greenpeace activist Watson in 1977, has chased the Japanese fleet hunting whales off Antarctica for several years in a bid to stop the animals being slaughtered.

Japan says it conducts vital scientific research using a loophole in an international ban on whaling, but makes no secret of the fact that the mammals ultimately end up as food.

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.

Between then and last week, when he unexpectedly announced his arrival by boat in Los Angeles, Watson said he was mostly at sea -- including from December to March with the Southern Ocean campaign, but only "as an observer."

In Tokyo, Deputy Chief Cabinet Secretary Katsunobu Kato responded to Watson's re-emergence on US soil by saying: "Japan continues to request the captain's arrest."

The eco-activist was not stopped by US immigration or other officials when he entered the country last week.

But he acknowledged that he could yet be arrested. "There's always a possibility," he said, while noting that: "Nobody gets extradited on a trespassing charge, it's political.

"They can try, but the US government is well aware of where I am. If there's any reason to deal with it (being arrested) we'll deal with it. I'm not going to make myself unavailable."

Watson said he thought Japan was pursuing the legal action partly to drain non-profit Sea Shepherd's coffers.

"Basically what they're doing is they're forcing us to spend a lot of money on that, hoping that that will stop us.

"But Sea Shepherd USA has already withdrawn from the campaign, the campaign is under the leadership of Sea Shepherd Australia and the ships are ready to leave on December 1," he said.

The veteran environmentalist, who was granted an Australian visa last week, had another reason to return to the United States, of which he is a citizen.

"It's been 15 months since I've been here. I left the week that my granddaughter was born so I haven't seen her for 15 months. So that was the most important thing about coming back."