We consider law and policy responses to invasive seaweeds at global and regional levels. Key global regimes considered include the 1982 United Nations Convention on the Law of the Sea, the Convention on Biological Diversity, the Ramsar Convention and the Bonn Convention on Migratory Species. Contributions from the Food and Agriculture Organization and the International Maritime Organization are also considered in the global context. At a regional level, examples of efforts in North America and Europe are offered to illustrate challenges and opportunities for regional responses to invasive seaweeds. We conclude with law and policy recommendations, most notably the need to approach the issue of invasive seaweeds in a manner consistent with the precautionary principle.