New restrictions on U.S. seafood imports, which will require seafood to be harvested in accordance with the U.S. Marine Mammal Protection Act (MMPA), will likely offer significant marine conservation benefits on a global scale. In this Policy Forum, Rob Williams et al. highlight the impacts and challenges involved in this endeavor. The U.S. is the largest importer of seafood in the world, accepting marine catches from more than 120 countries. Best case scenario, countries will comply and marine species will benefit from improved protection. Worst case, countries could suffer economically from not being able to export to the US, and/or choose not to comply. The new law, which comes into effect on January 1, 2017, prohibits intentionally harming marine mammals thorough fishing activities, and it requires bycatch to be kept within the limits of what marine mammal populations can sustain. However, the authors caution, some countries may choose not to comply, and many developing countries may be unable to comply due to lack of monitoring and enforcement capacity. To reduce these risks, Williams et al. urge the international community to support capacity-building efforts in the most economically vulnerable countries. Small Latin American countries and most of the Small Island Developing States (SIDS) are the most likely to struggle to meet these new regulations, the authors note; efforts to comply will need to be driven from within the countries themselves, but outside support and funding could increase the chances of success. Monitoring the abundance of certain marine species is a major challenge. For example, at this point only about 5% of the world's oceans are surveyed well enough to detect the presence of rare cetacean species or trends in common ones. Regional coordination, the author say, can help countries to share costs, ships, trained observers, analytical expertise, and data. The international community can support each of these efforts through both funding and building scientific capacity, the authors conclude.