Paul Watson was arrested in Germany in May on a Costa Rican extradition request.
He skipped bail earlier this month after learning Japan, too, was seeking his extradition from Germany.
The 61-year-old has issued a statement saying he's now in "a safe place far away from the scheming nations who have turned a blind eye to the exploitation of our oceans."
Watson says he expects Japanese whalers to "continue to exploit all avenues" to find a way to stop him.
He vows to set sail in December for the Southern Ocean Whale Sanctuary around Antarctica to intercept Japanese whaling ships.
Watson parted ways with Greenpeace in 1977 to set up Sea Shepherd.
The group has waged aggressive campaigns to protect marine animals, prompting Japan to labels its members terrorists and to seek Watson's arrest for allegedly masterminding violent protests.