His first taste of vengeance came in 1979, when he went after a notorious pirate whaling ship called the Sierra, which was barred from many ports in the world for violating anti-whaling laws and non-payment of fuel bills. Most of its crew had outstanding arrest warrants, the ship kept changing its flag, and it was thought to have killed at least 25,000 whales.
It took Watson a year to hunt down the ship, and then he rammed it at full speed and ripped open its hull. The Sierra limped into port and its owners spent $1 million on uninsured repairs. Then it sank at the dockside after Sea Shepherd operatives blew holes in its hull with limpet mines. Watson went on to sink three Norwegian whaling ships, two Icelandic whalers in Reykjavik harbour and half the Spanish whaling fleet. So why hasn’t he been convicted of a crime?
‘Because all those vessels were operating illegally and criminals do not generally want to go to court, and because we have the legal authority to do what we do,’ Watson says. ‘The United Nations World Charter for Nature, section 21, empowers any nongovernmental organisation or individual to uphold international conservation law in areas beyond national jurisdiction and specifically on the high seas.’ [2009 April] Paul Watson: Sea Shepherd eco-warrior fighting to stop whaling and seal hunts
http://www.whale.to/b/seashepherd.html