In Cartagena, Colombia, delegates from 170 nations are developing a treaty on the international trade in genetically-modified plants and other products. The U.S. delegation disagrees strongly with the trade limits proposed by developing countries, but ultimately it has no say in the matter: the Senate never ratified the 1992 convention from which this treaty arose. Living On Earth talks with Charles Margulis, a member of the Greenpeace delegation in Cartagena.