The WTO ruled yesterday that sea turtles endangered by shrimp fishers cannot be used as an excuse for trade discrimination.A WTO dispute panel in Geneva said the United States had no right to ban imports from Asian shrimp traders who failed to take measures to prevent sea turtles being killed. In Washington, U.S. environmental groups sharply criticised the WTO ruling against a U.S. law designed to protect endangered sea turtles from harmful shrimping practices.