Much of the literature on environmental protection focuses on domestic actors and domestic political activity. However, the degree to which environmental policies are influenced by international organizations and agendas is often overlooked. In the case of environmental policies in less developed countries, the role of the international system is particularly essential. Indeed, the international system is often the primary motivator of environmental protection policies in less developed countries. This paper demonstrates the strength of international influence in the case of one particular policy, Environmental Impact Assessment legislation. It argues that international environmental organizations, the international development bank community, and the international science community, have had central importance in the diffusion of Environmental Impact Assessment legislation, outweighing other factors such as the size of domestic environmental support or the degree of environmental degradation. This argument is supported by the results of an event history statistical analysis.