Does the “No-Harm’Rule” Have a Role in Preventing Transboundary Harm and Harm to the Global Atmospheric Commons from Geoengineering?

Solar Radiation Management (SRM) geoengineering poses a significant risk of transboundary and global atmospheric harm. How might international law regulate the future use of SRM? We explore how the ‘no-harm rule’ from customary international law might contribute to the international governance of future attempts at SRM. The no-harm rule imposes a legal duty on states to prevent significant damage across borders and in the global commons. Existing geoengineering literature assumes that, as the international law system lacks a mandatory enforcement mechanism, the no-harm rule will play little or no role in the governance of SRM. We challenge this assumption by focusing on the possibilities of compliance with the no-harm rule through bolstering its legitimacy and sense of legal obligation. We explain how Brunnée and Toope’s theory of ‘interactional international law’ might provide a useful lens for developing the no-harm rule in this way to independently respond to the risks posed by SRM.