This paper examines how humans have impacted upon the marine environment through the introduction of species beyond their native ranges. Introduced species impact upon native biodiversity, spread diseases and pathogens, and have had economic and social impacts in their ‘new’ ecosystems. Because of the range and extent of introduced species impacts, numerous methods to mitigate the effects of introduced species have been developed and implemented. Within this paper we will examine how two international legal instruments, the Convention on Biological Diversity, 1992 (CBD) and the World Trade Organization’s General Agreement on Tariffs and Trade 1994 (GATT), in particular its associated Agreement on the Application of Sanitary and Phytosanitary Measures (SPS), deal with introduced species. In this context, the paper focuses on the potential for conflict that may arise with the application of these international legal instruments, thus causing a failure to effectively mitigate for the effects of introduced species.