Capt. Paul Watson, founder of the Sea Shepherd Conservation Society and star of the popular reality show “Whale Wars,” has resigned as leader of the controversial group because of mounting legal challenges.

Watson, most famous for leading the group’s annual harassment campaigns against Japanese whaling efforts, last month was named in a U.S. court injunction that barred him from approaching to within 1,500 feet of the whaling ships.

In a statement published Monday on the Sea Shepherd website, Watson said:

“Because I have been personally named in the injunction I have resigned as the President of the Sea Shepherd Conservation Society in the United States and as President of the Sea Shepherd Conservation Society Australia. I have also resigned my position of Executive Director of Sea Shepherd Conservation Society USA and I will hold no paid position with Sea Shepherd anywhere Sea Shepherd is registered and operates as a non-profit organization in any nation.”

Leadership for Operation Zero Tolerance, the name for this season’s anti-whaling campaign, has been turned over to former Australian senator Bob Brown.

Watson, who holds dual U.S.-Canada citizenship, said he will still participate in the campaign, as an observer, but within guidelines of the injunction.

Meanwhile, TMZ is reporting that Watson has been sued by Ady Gil, who claims to have owned the anti-whaling boat of the same name. The Ady Gil, which was used by Sea Shepherd during the 2010 campaign against the whalers, sunk after being rammed.

Gil charges that Watson let the vessel sink rather than try to save it because that would generate more publicity, and is seeking more than $5 million in damages. (See ramming incident in video posted below.)

Sea Shepherd claims to have saved more than 4,000 whales from being killed by whalers. Japan annually sets a quota of nearly 900 minke whales and skirts a long-standing international moratorium against commercial whaling by claiming to be whaling in the name of science, under a lethal research loophole in the wording of the ban.

Sea Shepherd harassment tactics have included hurtling stink bombs and fouling propellers of Japanese ships, and the confrontations have been very tense, at times, and have included occasional vessel collisions.