The Sea Shepherd Conservation Society has agreed to stop disrupting Japan's annual whale hunts, ending a lengthy legal dispute in the US.
But the mediated settlement, between the group and Japan's whaling body, is expected to do little to end confrontations in the Southern Ocean.
Those operations are conducted by Sea Shepherd Australia, which said it was not affected by the court ruling.
Japan's whaling has been ruled illegal by the Australian Federal Court.
In 2015, the court fined whaling company Kyodo Senpaku Kaisha 1m Australian dollars ($760,000; £580,000) for catching minke whales within the waters of Australia's Antarctic whale sanctuary.
Jeff Hansen, managing director of Sea Shepherd Australia, told the BBC the US ruling would "absolutely not" affect its own operations.
He said if the ICC were to pursue Sea Shepherd in Australia "they would be entering into a court system they're in contempt of, and we would welcome that".
Despite an international moratorium on whaling, Japan's fleet sails to the Antarctic in the autumn or winter each year, returning the following spring. The most recent hunt had a quota of 333 minke whales.
Japan says the hunts are legal because they are conducted for scientific research, but activists say the programme is inhumane, unsustainable and illegal.
Every year, Sea Shepherd follows the whaling fleet to disrupt its activities.
Numerous collisions and clashes have occurred in the past, with each side blaming the other for aggressive tactics.
Under the settlement, as announced by Japan's government-backed Institute for Cetacean Research (ICR) on Tuesday, the Sea Shepherd Conservation Society agreed to stop "physically attacking" Japanese vessels and crew and "navigating in a manner that is likely to endanger their safe navigation".
The ruling concludes a case brought by the ICR in 2011.
Mr Hansen said in a statement that Sea Shepherd Australia "remains committed to upholding the Australian Federal Court ruling banning the slaughter of whales in the Australian Whale Sanctuary.
"We are not concerned about the US court settlement as it does not have any effect on Australian law."