Greenpeace activists visit a Walmart store. They deployed a balloon banner and cleared some tuna cans off the shelves as a message to the company and shoppers that Walmart can do more to protect the oceans and workers. Walmart's Great Value tuna is supplied by Thai Union, the world's largest canned tuna company and the subject of numerous investigations into human rights abuses at sea. While Thai Union has taken initial steps toward ridding its supply chains of labor abuses and seeking solutions to destructive fishing, Walmart has remained silent on its role in selling the potentially tainted seafood.