The conservation group Sea Shepherd on Monday asked the US Supreme Court to lift an order forcing it steer clear of Japan's whalers, who have warned of legal reprisals over harassment at sea.
Since 2002, Sea Shepherd has annually disrupted Japan's contested hunt in the Southern Ocean but a US court on December 17 issued an injunction for the activists to stay at least 500 yards (meters) away from the whaling vessels.
Environmental lawyer Robert F. Kennedy Jr., the son and namesake of the slain political icon, urged the United States to show support for the Sea Shepherd Conservation Society and its fugitive founder Paul Watson.
"It's a mission that only they are capable of accomplishing and that is absolutely vital to the enforcement of international agreements on the high seas which otherwise go unenforced," Kennedy told reporters.
The International Whaling Commission has designated a whale sanctuary in the Southern Ocean. Japan nonetheless kills whales in the area through a loophole in a 1986 moratorium on commercial whaling that allows lethal research.
Kennedy called Japan's government-supported Institute for Cetacean Research, which runs the whaling program and sued Sea Shepherd, "a pirate organization masquerading as a scientific research group."
In an application to the Supreme Court filed on Friday, Sea Shepherd and Watson said that the lower court "acted rashly" and voiced concern over the order's "extraordinarily long reach" to areas outside US jurisdiction.
The US Court of Appeals for the Ninth Circuit cited safety concerns when it issued the injunction, which remains in effect until a decision on the case.
Sea Shepherd released a letter from a lawyer representing the Japanese institute, which complained that the Brigitte Bardot, a former ocean racer named after the French actress and animal rights activist, violated the 500-yard injunction on January 29.
The letter warned that the institute could ask that Sea Shepherd be found in contempt of court -- which could lead to punishment -- unless the group orders the Brigitte Bardot to comply with the injunction or returns it to port.
The Oregon-based group contended that it is observing the injunction, saying that the Brigitte Bardot sails under an Australian flag and is operated by Sea Shepherd's Australian sister organization.
Japan, which makes no secret that meat from whaling ends up on dinner plates, accuses Western nations of disrespecting its cultural traditions.