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Are there international treaties affecting US geoengineering?
Executive summary
A patchwork of international agreements can and does affect aspects of U.S. geoengineering research and deployment, but no single multilateral treaty exclusively governs the full spectrum of geoengineering activities (including solar geoengineering) [1]. Key relevant instruments cited in recent reporting and analyses include the Environmental Modification Convention (ENMOD), the Convention on Biological Diversity (CBD) decisions that act as a de facto moratorium on many activities, the London Convention/Protocol and High Seas Treaty provisions for marine interventions, and customary international-law principles referenced by scholars and policy analysts [2] [3] [4] [5] [1].
1. The legal vacuum plus overlapping rules: “No single treaty rules it all”
Congressional Research and Library of Congress reporting states plainly: to date no multilateral treaty exists that was created specifically to govern the full range of geoengineering activities — meaning governance is a mosaic of applicable treaties, customary international law, and domestic law rather than a single binding framework for everything from solar aerosol injection to ocean CDR (carbon dioxide removal) [1]. Multiple commentators and legal scholars use that observation as the starting point for calls to either strengthen existing regimes or build a new SAI-specific (solar-aimed) treaty [6] [7].
2. ENMOD and the military angle: “Hostile use is banned, defensive ambiguity remains”
The Environmental Modification Convention (ENMOD) — negotiated after Cold War-era weather warfare experiments — prohibits military or hostile environmental modification techniques with widespread, long-lasting or severe effects, and it shaped U.S. policy dating to the 1970s [2]. ENMOD’s focus is on hostile uses, so while it constrains weaponization of weather or climate, available sources do not detail ENMOD as a comprehensive ban on peaceful or civilian geoengineering research and deployment; scholars point to interpretive and enforcement gaps [2].
3. Biodiversity Convention and the CBD “de facto moratorium”
The Convention on Biological Diversity and its subsidiary decisions (often referenced as a moratorium-style approach) have been interpreted by participants and civil-society advocates to prohibit many forms of geoengineering except limited, small-scale, transparent scientific research with environmental and social assessment requirements [3] [4]. Proponents of stricter rules point to the CBD as a highly restrictive instrument that should limit commercial or cross-border deployments [8].
4. Ocean governance: London Protocol/High Seas Treaty tighten marine CDR rules
Marine geoengineering and ocean-based CDR are constrained by maritime regimes: the London Convention/Protocol has amendments and guidance aimed at regulating or limiting marine geoengineering activities, and the new High Seas Treaty establishes impact-assessment and consultation duties that would make certain marine interventions harder to carry out without international oversight [3] [5]. Analysts note the High Seas Treaty requires notification and consultation for projects “that may cause substantial pollution or significant and harmful changes” — a direct governance lever on sea-based geoengineering [5].
5. Human-rights, environment, and UNCLOS pressures: “Multiple umbrellas apply”
Civil society and legal analysts argue that human-rights frameworks, the UN Framework Convention on Climate Change (UNFCCC) obligations, and UNCLOS pollution duties (and even advisory decisions by tribunals) collectively exert restrictive pressure on geoengineering activities — especially where cross-border impacts, pollution, or irreversible change are plausible [8] [9]. These overlapping obligations are cited as a practical constraint even absent an SAI-specific treaty [8].
6. Governance debates and the push for a dedicated treaty: “Many call for treaty-based SAI rules”
Policy scholars and law journals argue that customary law and patchwork treaties are insufficient to prevent unilateral or risky SAI deployment; recent proposals call for a treaty focused on SAI with binding commitments, institutional monitoring, and prohibition of unilateral action to avoid “it only takes one” scenarios [6] [7]. This is a contested policy prescription: some see adaptation of existing regimes as preferable, others insist on a new instrument [7].
7. Practical effect for U.S. action: constrained but not fully barred
Taken together, these instruments mean that U.S. geoengineering activities — particularly projects with international or transboundary effects or marine components — face legal and political constraints under ENMOD, CBD decisions, maritime law, and human-rights/environmental norms; at the same time, available sources emphasize gaps and enforcement limits and note that no all-encompassing multilateral prohibition exists for every form of geoengineering [2] [1] [8] [5].
Limitations and disagreements: reporting and legal studies agree on overlapping constraints but disagree on strength and sufficiency. Some advocates (e.g., CIEL) describe a “highly restrictive” existing framework and warn that commercial schemes breach it [8]; others and many scholars emphasize legal gaps and the need for an explicit, binding SAI treaty to prevent unilateral deployment [1] [6]. Available sources do not provide a definitive list of which specific U.S. domestic statutes would be triggered in each geoengineering scenario — that detail is not found in current reporting [1].