The advisory opinion delivered by the International Tribunal for the Law of the Sea (ITLOS) on May 21, 2024, that precedes the International Court of Justice (ICJ) advisory proceedings on “Obligations of States in respect of Climate Change”. It marks a significant milestone in international climate change litigation. This opinion, sought by the Commission of Small Island States on Climate Change and International Law (COSIS), addresses the specific obligations under the United Nations Convention on the Law of the Sea (UNCLOS) regarding climate change mitigation. This development precedes similar advisory proceedings by the International Court of Justice (ICJ), underscoring its importance in shaping international climate action.

New Elements in the ITLOS Opinion

1. Acceptance of COSIS Request:
   • Radical Step: ITLOS addressed obligations of states not party to the COSIS Agreement, expanding the scope of its advisory capacity.
   • Obligations under UNCLOS Article 194(1): States must take all necessary measures to prevent, reduce, and control marine pollution from anthropogenic greenhouse gas emissions (GHGs).
2. Clarification on Carbon as a Pollutant:
   • Carbon Dioxide Qualification: The opinion clarified that CO2 release into the marine environment is a potential deleterious substance under UNCLOS Article 1(1)(4).
   • Scientific Position: The surface ocean absorbs about a quarter of atmospheric CO2, causing acidification and absorbing excess heat, contributing to sea-level rise.

Understanding the Legal Importance

1. Principle of Prevention/No Harm Rule:
   • State Behavior Regulation: This rule faces limitations in climate regulation due to its bilateral nature and issues of attribution and standing.
   • Collective Interest vs. Bilateral Interests: The opinion acknowledges climate change as a collective interest, advocating for measures aligned with the best available science and international agreements like the UNFCCC and the Paris Agreement.
2. Obligation and Due Diligence:
   • Stringent Due Diligence Obligation: High risks of harm to the marine environment from emissions necessitate stringent standards.
   • General Nature of Obligations: States are required to reduce GHG emissions over time, emphasizing gradual reduction while not specifying immediate or eventual cessation.
3. States’ Discretion:
   • General Obligations: While broad, these obligations underline that states do not have unfettered discretion in climate change action, though the general nature may be more symbolic.

Case Example: Urgenda Foundation vs The Netherlands

• Dutch Supreme Court Decision: Required the Netherlands to reduce GHG emissions to 25% below 1990 levels by 2020, using scientific estimates and least cost methods.
• ITLOS Methodology Gap: The ITLOS opinion does not specify a methodology for assessing states’ mitigation action levels, unlike the Urgenda judgment.

Equity and Means

• Principle of Equity: Measures must consider states’ capabilities and available means, emphasizing equity in determining the requisite level of action.

Political and Legal Impact

• Advisory Opinion’s Influence: While lacking legal force, the advisory opinion holds significant political influence as an authoritative judicial pronouncement.

Challenges and Way Forward

Challenges

1. Broad and General Obligations: The ITLOS opinion provides broad directives which may lack specificity, making it challenging to enforce concrete actions.
2. State Discretion and Compliance: States may interpret their obligations variably, potentially undermining consistent global climate action.
3. Lack of Methodology: Absence of a concrete methodology for assessing mitigation actions leaves room for discrepancies in states’ commitments and efforts.
4. Equity and Capability Considerations: Balancing equity and varying state capabilities can complicate the implementation of uniform climate action measures.

Way Forward

1. Defining Specific Obligations: Develop more detailed guidelines and criteria to clarify the general obligations outlined by ITLOS, ensuring clearer implementation pathways.
2. Strengthening International Cooperation: Enhance collaborative efforts through international frameworks like the UNFCCC and the Paris Agreement to align state actions with global climate goals.
3. Establishing Assessment Methodologies: Create standardized methodologies to evaluate states’ mitigation efforts, similar to the approach in the Urgenda case, providing a clearer benchmark for compliance.
4. Promoting Equity in Climate Action: Ensure that climate action measures consider the diverse capacities and resources of states, promoting fairness and encouraging participation from all nations.
5. Leveraging Political Influence: Utilize the political significance of advisory opinions to galvanize international support and commitment towards stronger climate action.

The ITLOS advisory opinion represents a crucial step towards enhancing international legal frameworks for climate change mitigation. However, addressing the outlined challenges and pursuing a comprehensive and equitable approach will be essential for meaningful progress in global climate action.