The Environmental Modification Convention: Revisiting the Treaty for Contemporary Climate Engineering Governance

Abstract 

As the climate crisis worsens, climate engineering is gaining attention as a possible way to cool  the planet. But the existing legal framework, especially the 1977 Environmental Modification  (ENMOD) Convention, wasn’t built to regulate peaceful interventions. This article examines  ENMOD’s limited scope, arguing that its focus on “hostile use” makes it outdated for governing  modern technologies like solar radiation management, carbon removal. By comparing ENMOD  with more recent agreements like the Convention on Biological Diversity and the Paris Agreement,  the paper reveals major legal and institutional gaps. It concludes that a reformed, cooperative  governance framework, grounded in precaution, transparency, and human rights, is urgently  needed to ensure that climate engineering serves humanity without creating new global risks. 

1. Introduction 

1.1. Context and Significance 

The world is facing a serious threat from climate change, and so far, efforts to cut greenhouse gas  emissions have not been enough. This has forced policymakers to consider Climate Engineering  (Geoengineering) as a possible way to rapidly bring down global temperature.1 These are  deliberate large-scale human interventions such as injecting aerosols into the stratosphere to reflect  sunlight, i.e., Solar Radiation Management (SRM), or Massive Carbon Capture Schemes (CDR), which promise potential global temperature reduction yet also risk unpredictable transboundary  consequences.2 For instance, if rainfall is artificially increased or decreased in one region, it could  trigger floods or droughts in neighboring countries. In 2009, a cloud seeding effort near Beijing  intended to induce local rainfall accidentally triggered the city’s largest snowfall in decades.3 Similarly, the U.S. project STORMFURY to weaken the hurricanes showed how even small  interventions can have far-reaching effects.4 These concerns are prompting scientists and legal  experts to reassess whether existing environmental laws are equipped to govern such emerging  technologies. 

Efforts to regulate environmental modification began during the Cold War, primarily in reaction  to the military use of weather modification during the Vietnam War.5 This led to the adoption of  the ENMOD (Convention on the Prohibition of Military or Any Other Hostile Use of  Environmental Modification Techniques) in 1976.6It bans hostile environmental modification for  military purposes, but it was not designed with peaceful climate engineering purposes in mind. As  a result, these powerful techniques are currently unregulated in their non-hostile use, which means  a state could initiate a geoengineering project with genuinely peaceful intentions yet still  accidentally cause catastrophic harm, such as an unseasonal drought or flood in a neighboring  nation.7 While ENMOD effectively prevents environmental warfare, it doesn’t address the  deliberate manipulation of natural systems for seemingly harmless scientific or environmental  goals.8 

1.2. Core Issue 

The central issue lies in ENMOD’s outdated framework. Its regulatory reach is strictly limited by  the text of Article I, which requires clear evidence of a “military or any other hostile use”, and its  criteria – “widespread,” “long-lasting,” and “severe”– are vague and based on 1970s technology.9 Meanwhile, Article III explicitly allows environmental modification for “peaceful purposes.”10 But modern climate interventions might have global consequences even without any hostile intent. Without a clear international framework to regulate such activities, we are left with a legal gap that could fuel potential conflict.11 

1.3. Objective and Scope 

This article aims to: 

• Evaluate ENMOD’s applicability to modern climate engineering. 
• Identify legal and institutional gaps in the existing framework. 
• Compare ENMOD with other international environmental instruments, such as the  Convention on Biological Diversity (CBD)12 and the Paris Agreement.13
• Propose a constructive way forward for international governance of climate engineering. 

1.4. Thesis Statement 

Although the ENMOD Convention succeeded in outlawing environmental modification for  military purposes, it remains legally obsolete in regulating peaceful climate intervention.14 A  reformed, cooperative, and transparent governance mechanism, rooted in international  environmental and human rights law, is urgently needed to ensure that climate engineering does  not become a legally ungoverned frontier.15 

2. Research Methodology 

2.1. Approach 

This study adopts an analytical and doctrinal approach, examining the ENMOD Convention’s  text, related treaties, and key international environmental law cases to uncover structural  weaknesses. It also incorporates a comparative analysis of current policy debates and scientific  developments to assess the Convention’s relevance in today’s climate governance landscape. 

2.2. Sources 

Primary sources include: 

• The ENMOD Convention (1977).16
• The Convention on Biological Diversity (1992).17
• The Paris Agreement (2015) and UNFCCC (1992).18
• ICJ jurisprudence, particularly the Trail Smelter Arbitration (1938–41),19Nuclear Weapons Advisory Opinion (1996)20, and Pulp Mills on the River Uruguay (2010).21
• Official UNEP, IPCC, and UNEA reports on geoengineering.22Secondary sources include academic journals such as the European Journal of International Law,  Cambridge International Law Journal, and policy analysis by the Royal Society and Oxford  Geoengineering Program.23 

3. Legal Framework Governing Climate Engineering 

3.1. The ENMOD Convention (1977): Purpose and Limitations 

The Convention on the Prohibition of Military or Any Other Hostile Use of Environmental  Modification Techniques (ENMOD) was adopted in 1976 and entered into force in 1978 under  United Nations backing.24 It arose from Cold War concerns that countries might start using the  environment itself, like changing the weather, triggering earthquakes, or altering ocean currents,  as a weapon of war.25 The treaty’s preamble underscores the “welfare of mankind” and the  “preservation and improvement of the environment,” which sounds too broad and idealistic.  

However, its operative clauses are narrowly framed. 

Article I of ENMOD bans “military or any other hostile use of environmental modification  techniques having widespread, long-lasting or severe effects.”26 But it doesn’t define “hostile use” or clarify whether peaceful, research-driven activities with potential cross-border impacts fall  within its scope. This ambiguity shows that the treaty’s framers envisioned environmental warfare,  not climate interventions for mitigation or carbon removal. 

ENMOD prohibits environmental modification with “widespread,” “long-lasting,” or “severe”  effects, but it doesn’t define these terms in measurable ways.27Without clear thresholds, states may  interpret them differently, making enforcement unpredictable. This vagueness creates uncertainty  and undermines consistent compliance. 

Article II broadly defines “environmental modification techniques” as any deliberate  manipulation of natural processes affecting the Earth’s dynamics, composition, or structure,  including the biota, lithosphere, hydrosphere, atmosphere, and even outer space.28 Based on this  definition, modern climate engineering projects clearly constitute an “environmental  modification”. But since ENMOD only bans hostile uses and not peaceful ones, it doesn’t apply  to modern climate interventions, even if they might have serious effects across borders. 

Article V of ENMOD outlines a weak enforcement mechanism, relying on consultations between  states and, if needed, referral to the UN Security Council.29 Unlike the Chemical Weapons  Convention (CWC), it lacks an independent body for investigation or enforcement.30 This  reliance on political processes has left ENMOD largely inactive; no formal complaints have ever  been filed under its provisions.31 

ENMOD was written more than forty years ago, long before today’s global environmental  frameworks like the UNFCCC or the Convention on Biological Diversity (CBD) even existed. As  a result, it lacks the conceptual tools needed to address today’s climate challenges, like human caused climate change, CDR, and SRM. These issues weren’t on the radar back then, so the treaty  feels outdated when applied to today’s environmental realities. 

3.2. Related International Legal Frameworks 

• Convention on Biological Diversity (CBD), 1992: At COP 10 in 2010, the parties  adopted Decision X/33, which called for a moratorium on geoengineering activities that  could affect biodiversity. The idea was to hold on until there’s enough scientific  understanding and proper governance. However, this decision is non-binding and lacks enforcement.32 
• United Nations Framework Convention on Climate Change (UNFCCC), 1992, and  Paris Agreement, 2015: These agreements focus on emission reduction and adapting to  climate change, not on deliberate environmental modification.33 Still, Article 4 of the Paris  Agreement emphasizes the balance between mitigation technologies and environmental  integrity. While it’s not a direct reference to geoengineering, it does open the door for future  regulation in that space.34
• International Law Commission (ILC) Draft Articles on Prevention of Transboundary  Harm (2001): These codify the “no-harm principle,” requiring states to prevent activities  within their jurisdiction from causing significant transboundary environmental damage.35 This customary norm, articulated in the Trail Smelter case, could extend to geoengineering  activities.36

Other Relevant Principles 

• Precautionary Principle (Rio Declaration, Principle 15): Take preventive action even if  scientific evidence is uncertain.37
• Polluter Pays Principle (OECD Guidelines, 1972): Those who cause environmental harm  should bear the cost.38
• Intergenerational Equity (Stockholm Declaration, Principle 1): Protect the environment for  future generations.39

Together, these sources show that while no unified legal framework for climate engineering exists,  a growing patchwork of international norms and principles could guide future regulation,  especially for peaceful interventions beyond ENMOD’s narrow focus on warfare. 

4. Judicial and Scholarly Interpretation 

4.1. Key Judicial Precedents 

While no case directly addresses climate engineering, key international rulings establish principles like the duty to prevent transboundary harm that could guide future geoengineering governance.

1. Trail Smelter Arbitration (U.S. v. Canada, 1938–41): 

Established the foundational rule: “no state has the right to use its territory in a manner that  causes injury to another.” Although the dispute involved cross-border air pollution from a  Canadian smelter affecting U.S. farmland, this principle has become a cornerstone for  transboundary environmental accountability and is directly applicable to potential harms from  geoengineering.40 

2. Legality of the Threat or Use of Nuclear Weapons (ICJ, Advisory Opinion, 1996): 

The ICJ affirmed that states must protect the environment even during armed conflict. By  recognizing environmental preservation as part of customary international law, the Court  reinforced that environmental integrity is a core obligation under international law, not a secondary concern.41 

3. Pulp Mills on the River Uruguay (Argentina v. Uruguay, ICJ, 2010): 

Reiterated the duty of states to conduct Environmental Impact Assessments (EIAs) for  activities with potential cross-border effects. Although the dispute involved a pulp mill on a  shared river, the ruling has broader relevance: states considering large-scale interventions like  geoengineering must first undertake transparent EIAs and notify affected parties.42 

4.2. Scholarly and Policy Perspectives 

• Rayner et al. (Oxford Principles on Geoengineering Governance, 2009) propose five  guiding norms: (1) geoengineering as a public good, (2) public participation, (3)  transparency, (4) governance before deployment, (5) liability and redress mechanisms.43
• UNEP’s 2023 Report on Climate Intervention Governance warns that the absence of  regulation could lead to “unilateral deployment and geopolitical destabilization.”44
• Daniel Bodansky (EJIL, 2012) argues that the current patchwork of environmental law  lacks coherence for climate engineering, necessitating a specialized protocol under the  UNFCCC.45
• Alan Boyle and Christine Chinkin (2019) emphasize integrating human rights law into  climate engineering governance, particularly regarding informed consent and  intergenerational equity. Informed consent ensures that vulnerable communities have a  voice in decisions affecting their environment and health.
• Intergenerational equity demands that today’s actions do not unfairly harm future generations.46 

This discourse reinforces the growing consensus that ENMOD’s military-oriented framework is ill-suited to the contemporary scientific and ethical complexities of geoengineering. 

5. Critical Analysis 

5.1. Gaps and Ambiguities in ENMOD 

1. Technological Obsolescence 

ENMOD was drafted long before geoengineering techniques like Stratospheric  Aerosol Injection (SAI) and Ocean Fertilization became scientifically feasible. 

Its framers couldn’t anticipate interventions with potential global effects that are  peaceful in intent. Thus, the treaty doesn’t offer clear guidance for managing the risks tied to these emerging technologies.47 

2. Ambiguity in Definitions 

Terms like “widespread,” “long-lasting,” and “severe” lack quantitative  benchmarks, creating legal uncertainty. 

Small-scale but cumulatively impactful interventions may not trigger ENMOD  obligations, despite causing environmental harm.48 

3. Exclusion of Peaceful Purposes 

Article III (1) preserves the right to use environmental modification for peaceful  purposes, which inadvertently exempts potentially risky research or mitigation  projects. 

This gap opens the door to unilateral experimentation, where states or private actors  might proceed without international oversight or accountability.49 

4. Weak Enforcement 

Reliance on the UN Security Council for dispute resolution makes compliance  politically dependent. 

There is no independent verification or monitoring system, unlike conventions such  as the Chemical Weapons Convention (CWC) or Montreal Protocol.50 

5.2. Accountability and Risk Management Challenges 

• Transboundary Harm: Peaceful geoengineering projects may produce unintended effects  in distant states, raising questions about liability under customary international law. The  idea of state liability for cross-border environmental harm is part of customary law, but  applying it to climate engineering is still legally uncertain.51
• Due Diligence and Notification: ENMOD doesn’t require countries to carry out EIAs for  research-based climate interventions, unlike the UNFCCC or Pulp Mills jurisprudence.52
• Civil Society Participation: Lack of mechanisms for public consultation in decisions  involving geoengineering undermines transparency and democratic oversight.53

5.3. Comparative and Policy Approaches 

• European Union: Advocates a precautionary, science-based approach to climate  engineering. Its proposals include mandatory EIAs before any intervention.54
• United States: Supports small-scale geoengineering experiments, but emphasizes national governance rather than international legal frameworks.55
• China: Focuses on research under domestic scientific programs. So far, it hasn’t played a  major role in engaging in international discussions on climate engineering.56
• Oxford Principles (2009): Recommend governance prior to deployment, transparency,  public participation, and liability mechanisms.57

These comparative insights highlight the absence of a coordinated global governance  framework for climate engineering. 

6. Recent Developments 
7. UN Climate Conferences (COP27–COP29) 

Discussions increasingly focus on climate technologies, including CDR and SRM,  with calls for internationally agreed guidelines.58 

2. IPCC AR6 (2021–2022) 

Acknowledges that geoengineering could complement mitigation efforts, but warns  

that these technologies come with major uncertainties, requiring regulatory  oversight.59 

3. UNEA-6 (2024–2025) 

UNEP resolutions urge transparency and environmental due diligence before any  climate intervention, signaling emerging international consensus for governance  mechanisms.60 

4. Policy and Academic Advocacy 

Calls for a dedicated “Geoengineering Protocol” under UNFCCC to standardize  research, monitoring, and liability measures.61 

NGOs and think tanks emphasize intergenerational equity, human rights, and  biodiversity protection as guiding principles.62 

7. Way Forward 

7.1. Reforming and Updating the ENMOD Convention 

To make ENMOD responsive to present realities, its Article I should be reinterpreted or amended to cover any deliberate large-scale alteration of the environment that may have transboundary or  unintended impacts, irrespective of military intent. Clearer definitions of “widespread,” “long lasting,” and “severe” should also be adopted, aligned with modern scientific assessments and  international environmental standards.63 

7.2. Developing a Specialized Protocol under Existing Frameworks 

Rather than drafting an entirely new treaty, a more practical step would be to create a Specialized  Protocol on Climate Engineering under the UNFCCC or CBD.64 This protocol should: 

• Define permissible interventions and set scientific risk thresholds. 
• Establish clear liability rules, incorporating the principle of strict and absolute liability for  transboundary harm.65
• Require prior notification and consent of potentially affected states before any  experimental or large-scale deployment.66

7.3. Institutional and Oversight Mechanisms 

To ensure compliance, there should be: 

• An Independent International Monitoring Authority under UNEP or UNFCCC,  empowered to evaluate, approve, and supervise all climate engineering projects.67
• A Global Registry for recording and reviewing every geoengineering experiment. This  will improve transparency, prevent secret experimentation, and ensure global awareness.68
• An International Review Panel comprising experts in climate science, international law, ethics, and human rights to assess each proposal’s legality and potential consequences.69

7.4. Strengthening Legal and Ethical Safeguards 

Before any project proceeds, a mandatory EIA and public consultations involving local and  Indigenous communities are required.70Governance frameworks must: 

• Incorporate human rights safeguards, including protection of communities  disproportionately affected.71
• Enforce the precautionary principle, ensuring that no intervention proceeds until its  impacts are scientifically understood.72
• Emphasize transparency and accountability at every stage, from research to deployment.73

7.5. Accountability and Dispute Resolution 

A revised framework should embed customary international law principles such as the no-harm  rule; due diligence obligation.74Disputes arising from transboundary impacts can be referred to: 

• The International Court of Justice (ICJ), or a newly created International Tribunal on  Climate Engineering, specializing in environmental and technological disputes.75

Compensation and redress mechanisms must be clear; if a state’s intervention causes adverse  effects in another, that state should be held responsible under the doctrine of state liability.76 

7.6. Integrating Science, Law, and Policy 

• Encourage ongoing scientific research within a legally regulated space to balance  innovation with safety.77
• Build cooperation between climate scientists, legal scholars, and ethicists to ensure well informed policymaking.78 

• Promote capacity-building and public education so that all nations, including developing  ones, can participate equally in discussions about global climate interventions.79

8. Conclusion 

The ENMOD Convention was a landmark instrument when adopted. However, it falls short in  today’s context of climate engineering. Its narrow focus on military use and vague thresholds leave  modern interventions largely unregulated.80 Without a clear international framework, states or  private actors could engage in unilateral projects, potentially causing environmental or geopolitical  risks.81 To ensure climate engineering contributes positively to global climate mitigation, the  international community must adopt a coordinated and enforceable governance framework: 

Build on existing environmental treaties such as the UNFCCC, CBD, and Paris Agreement.82  Embed human rights norms, ensuring protection of vulnerable communities.83  Apply the precautionary principle and conduct mandatory EIAs.84 

Promote scientific collaboration alongside legal oversight to prevent harm.85 

A combined approach, updating ENMOD and creating a Specialized Protocol on Climate  Engineering, would enable effective regulation while preserving space for innovation.86 Only  through such balanced governance can climate engineering advance responsibly, aligning  scientific progress with fairness, transparency, and intergenerational justice.87 

9. Bibliography 

Primary Sources 

1. Convention on the Prohibition of Military or Any Other Hostile Use of Environmental  Modification Techniques (ENMOD), Nov. 18, 1976, 1108 U.N.T.S. 151. 
2. Convention on Biological Diversity, June 5, 1992, 1760 U.N.T.S. 79. 
3. United Nations Framework Convention on Climate Change (UNFCCC), May 9, 1992,  1771 U.N.T.S. 107. 
4. Paris Agreement, Dec. 12, 2015, UN Doc. FCCC/CP/2015/L.9/Rev.1. 
5. Trail Smelter Arbitration (U.S. v. Can..), 3 R.I.A.A. 1905 (1938–41). 
6. Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion, ICJ Rep. 226 (1996). 7. Pulp Mills on the River Uruguay (Arg. v. Urug.), ICJ Rep. 14 (2010). 
7. United Nations Environment Programme (UNEP), Climate Intervention Governance,  UNEP Report (2023). 
8. United Nations Environment Assembly (UNEA-6) Resolutions on Climate Intervention,  2024–2025. 

Secondary Sources 

1. Rayner, S., et al., Oxford Principles on Geoengineering Governance 2009. 
2. Bodansky, D., Climate Engineering and International Law, 23 EUR. J. INT’L L. 345  (2012). 
3. Boyle, A. & Chinkin, C., The International Law of Human Rights and Climate  Engineering, 31 CAMBRIDGE INT’L L.J. 112 (2019). 
4. Royal Society, Geoengineering the Climate: Science, Governance and Uncertainty (2009). 
5. IPCC, Sixth Assessment Report (AR6), Climate Change 2021–2022, Intergovernmental  Panel on Climate Change (2022).

1 Royal Soc’y, Geoengineering the Climate: Science, Governance and Uncertainty (Sept. 2009).

2Intergovernmental Panel on Climate Change (IPCC), AR6 Synthesis Report (2022). 

3 Ying Liu et al., Cloud Seeding and Precipitation Enhancement in Beijing, J. Applied Meteorology & Climatology,  48 J. Appl. Meteorol. Climatol. 1670, 1672 (2009).

4 William M. Gray & Neil L. Frank, Project STORMFURY: A Scientific Chronicle, 34 BULL. AM.  METEOROLOGICAL SOC’Y 373 (1973). 

5 Richard A. Clark, Weather Modification and Warfare: The Vietnam Experience, 22 AIR UNIV. REV. 30 (1971).

6 Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques, art.  I–III, Dec. 10, 1976, 1108 U.N.T.S. 151 [hereinafter ENMOD Convention]. 

7 Alan Boyle, State Responsibility and Liability for Transboundary Environmental Harm, 14 YEARSBOOK INT’L  ENV’T L. 43, 47 (2003). 

8 Daniel Bodansky, The Legal Framework for Geoengineering: Uncertainty and Promise, 7 CARBON & CLIMATE  L. REV. 227, 230 (2013). 

9 ENMOD, supra note 6, art. I. 

10 Id. art. III.

11 Alan Boyle & Christine Chinkin, The Making of International Law 143 (2007). 

12 Convention on Biological Diversity, opened for signature June 5, 1992, 1760 U.N.T.S. 79.

13 Paris Agreement, Dec. 12, 2015, T.I.A.S. No. 16-1104. 

14 Bodansky, The Legal Framework for Geoengineering, supra note 8, at 232. 

15 Boyle & Chinkin, The Making of International Law, supra note 11, at 145.

16 ENMOD Convention, Dec. 10, 1976, 1108 U.N.T.S. 151. 

17 Convention on Biological Diversity, June 5, 1992, 1760 U.N.T.S. 79. 

18 United Nations Framework Convention on Climate Change, May 9, 1992, 1771 U.N.T.S. 107; Paris Agreement,  Dec. 12, 2015, T.I.A.S. No. 16-1104. 

19 Trail Smelter Arbitration (U.S. v. Can.), 3 R.I.A.A. 1905 (1941). 

20 Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion, 1996 I.C.J. 226 (8 July 1996). 21 Pulp Mills on the River Uruguay (Arg. v. Uru.), Judgment, 2010 I.C.J. 14 (20 Apr. 2010).

22 United Nations Environment Programme, Emissions Gap Report (2023); Intergovernmental Panel on Climate  Change, Climate Change 2023: Synthesis Report (2023); United Nations Environment Assembly, Resolution on  Geoengineering and Governance of Climate Intervention (Mar. 2022). 

23 Steve Rayner et al., The Oxford Principles for the Governance of Geoengineering Research, 14 Carbon Mgmt. 233  (2009); Royal Society, Geoengineering the Climate: Science, Governance and Uncertainty (2009). 24 ENMOD Convention, supra note 6. 

25 Richard A. Clark, Weather Modification and Warfare: The Vietnam Experience, 22 AIR UNIV. REV. 30, 30–31  (1971).

26 ENMOD, supra note 6, art. I. 

27 Id. 

28 Id. art. II. 

29 Id. art. V. 

30 Boyle & Chinkin, Making of International Law, supra note 11, at 145. 

31 Bodansky, supra note 8, at 232.

32 Convention on Biological Diversity, Decision X/33, COP 10, Nagoya, Japan (Oct. 29, 2010),  https://www.cbd.int/decision/cop/?id=12260. 

33 United Nations Framework Convention on Climate Change, May 9, 1992, 1771 U.N.T.S. 107. 34 Paris Agreement, supra note 18, art. 4. 

35 International Law Commission, Draft Articles on the Prevention of Transboundary Harm from Hazardous Activities,  with Commentaries, 2001, U.N. Doc. A/56/10. 

36 Trail Smelter Arbitration, supra note 19. 

37 Rio Declaration on Environment and Development, Principle 15, U.N. Doc. A/CONF.151/26/Rev.1 (1992).

38 Organization for Economic Co-operation and Development (OECD), Recommendation on Guiding Principles  Concerning the International Economic Aspects of Environmental Policies (1972). 

39 Stockholm Declaration, Principle 1, U.N. Doc. A/CONF.48/14/Rev.1 (1972). 

40 Trail Smelter Arbitration, supra note 19.

41 Legality of the Threat or Use of Nuclear Weapons, supra note 20, at 235. 

42 Pulp Mills on the River Uruguay, supra note 21. 

43 Rayner et al., Oxford Principles, supra note 23, at 235. 

44 UNEP, Emissions Gap Report, supra note 22. 

45 Bodansky, Legal Framework for Geoengineering, supra note 8, at 232. 

46 Boyle & Chinkin, Making of International Law, supra note 11, at 145.

47 ENMOD Convention, supra note 6, art. I. 

48 Id. art. I. 

49 Id. art. III.

50 Chemical Weapons Convention, opened for signature Jan. 13, 1993, 1974 U.N.T.S. 45.

51 ILC Draft Articles on Prevention of Transboundary Harm, supra note 35. 

52 Pulp Mills on the River Uruguay, supra note 21, at 35–37. 

53 United Nations Environment Programme (UNEP), Governing Climate Engineering: Principles and Guidelines 23– 24 (2023). 

54 European Commission, Report on Environmental Governance and Geoengineering, COM (2018) 235 final, at 5–6  (EU). 

55 U.S. Nat’l Research Council, Climate Intervention: Reflecting Sunlight to Cool Earth, at 45–46 (2015).

56 Chinese Acad. of Sci., National Geoengineering Program Overview, at 12–14 (2020). 

57 David W. Keith et al., The Oxford Principles, 2 Climatic Change 1, 3–5 (2009).

58 United Nations Framework Convention on Climate Change (UNFCCC), Report of COP27, UN Doc.  FCCC/CP/2022/10 (Dec. 18, 2022). 

59 Intergovernmental Panel on Climate Change (IPCC), AR6 Climate Change 2021: The Physical Science Basis 112– 15 (2021–2022). 

60 United Nations Environment Assembly (UNEA-6), Resolutions on Climate Intervention and Governance,  UNEP/EA.6/Res.5 (Mar. 3, 2025). 

61 Oxford Geoengineering Program, Proposal for a UNFCCC Geoengineering Protocol 7–9 (2023).

62 Boyle & Chinkin, Making of International Law, supra note 11, at 20-21.

63 UNEP, Environmental Modification Techniques: Scientific and Legal Assessment 18–20 (2023).

64 Bodansky, The Legal Framework for Geoengineering, supra note 8, at 120-122. 

65 Ibid. 

66 Oxford Geoengineering Program, Proposal for a UNFCCC Geoengineering Protocol 7–9 (2023).

67 UNEP, Report on Climate Intervention Governance 12–14 (2023). 

68 Ibid.

69 Boyle & Chinkin, Making of International Law, supra note 11, at 220-221. 

70 Pulp Mills on the River Uruguay, supra note 21, at 42-44. 

71 Boyle & Chinkin, supra note 11, at 222. 

72 Rio Declaration on Environment and Development, princ. 15, U.N. Doc. A/CONF.151/26 (1992).

73 Bodansky, supra note 8, at 125. 

74 Trail Smelter Arbitration, supra note 19. 

75 Ibid.; Bodansky, supra note 8, at 130. 

76 Rayner, et al., supra note 11, at 7–8. 

77 UNEP, supra note 22, at 21–23.

78 Boyle & Chinkin, supra note 11, at 224. 

79 Bodansky, supra note 8, at 132–33. 

80 Rayner, et al., Oxford Principles on Geoengineering Governance 3–5 (2009). 

81 UNEP, Environmental Modification Techniques: Scientific and Legal Assessment 18–20 (2023).

82 Paris Agreement, Dec. 12, 2015, U.N. Doc. FCCC/CP/2015/L.9/Rev.1; Convention on Biological Diversity, June  5, 1992, 1760 U.N.T.S. 79. 

83 Boyle & Chinkin, Integrating Human Rights in Climate Engineering Governance, 31 EUR. J. INT’L L. 211, 220– 22 (2019). 

84 Pulp Mills on the River Uruguay, supra note 21 at 42–44. 

85 UNEP, supra note 22, at 21–23. 

86 Bodansky, supra note 8, at 130–32. 

87 Rayner, et al., supra note 23, at 7–8.