A federal appeals court has likened a confrontational anti-whaling group to pirates in a ruling that blocks the activists from approaching Japanese whalers.

A three-judge panel of the U.S. 9th Circuit Court of Appeals issued a ruling late Monday that ordered the Sea Shepherd Conservation Society to remain 500 feet from Japanese whalers at sea.

“You don’t need a peg leg or an eye patch,” 9th Circuit Chief Judge Alex Kozinski wrote for the court. "When you ram ships, hurl glass containers of acid, drag metal-reinforced ropes in the water to damage propellers and rudders, launch smoke bombs and flares with hooks, and point high-powered lasers at other ships, you are, without a doubt, a pirate, no matter how high-minded you believe your purpose to be.”

The panel overturned a lower court’s decision refusing to order the activists to stay away from whalers. The 9th Circuit issued an injunction in December and explained its reasoning in this week’s ruling.

“Cetacean’s uncontradicted evidence is that Sea Shepherd’s tactics could immobilize Cetacean’s ships in treacherous Antarctic waters,” Kozinski wrote.

The decision stemmed from a lawsuit by the Institute of Cetacean Research, a Japanese group that hunts whales in the Southern Ocean. The U.S., Japan and many other countries have agreed to abide by an international convention that authorizes whale hunting when done with a research permit.