Watson said he was giving up running the organization to comply with a U.S. court's temporary injunction, The Sydney Morning Herald reported. He said he would comply with the order to stay at least about 1,500 feet from Japanese whaling vessels.
''As a U.S. citizen, I will respect and comply with the ruling of the U.S. 9th District Court and will not violate the temporary injunction granted to the Institute for Cetacean Research,'' he said.
Brown, who resigned last year as the Greens leader, said he is now the active head of Sea Shepherd. The group is using four vessels this year in its annual campaign against the Japanese antarctic whaling fleet and Brown said he and Jeff Hansen, Sea Shepherd's Australian manager, are running the operation.
''He's behind the scenes, but he's not in charge of the operation,'' Brown said of Watson. ''I'll be every day working, as will Jeff, working with the Sea Shepherd fleet under the authority of Sea Shepherd Australia, to make sure this mission is successful.''
Japan is seeking Watson's arrest and has obtained a "red notice" from Interpol. He is on board the Steve Irwin, the group's flagship, outside of any national jurisdiction.
Watson, a native of Toronto, has joint U.S.-Canadian citizenship.