Although some species fall solely within the jurisdiction of one country, it is common for species to fall outside of one state’s exclusive control. The United States protects endangered species in its territory and in international waters through the Endangered Species Act (ESA). But the extent of U.S. jurisdiction under the ESA is largely untested, and endangered species policy interacts with international law. This Article clarifies the protections of the ESA in U.S. jurisdiction and maritime regimes. It makes evident that the United States’ narrow application of the ESA does not align with established principles of extraterritoriality or customary international law. It also illuminates the need for broader international actions to protect endangered species.