기후변화와 관련된 국가의 의무에 관한국제사법재판소 권고적 의견의 정책적 시사점

The International Court of Justice (ICJ) issued its Advisory Opinion on States’ Obligations Relating to Climate Change on 23 July 2025. This opinion is significant in that it articulates in detail the obligations of States regarding greenhouse gas emission reductions and sets out relatively clear criteria for assessing compliance with these obligations. This paper summarizes the key contents of the ICJ’s Advisory Opinion concerning the preparation, communication, and maintenance of nationally determined contributions (NDCs) and the implementation of domestic mitigation measures. It also draws out the implications of the opinion for national climate policy. With regard to NDCs, the ICJ held that limiting warming to 1.5°C has become a “scientifically based consensus target.” The Court found that the obligation to prepare, communicate, and maintain successive NDCs is an obligation of result with procedural characteristics. However, the mere formal preparation and communication of an NDC is not sufficient to comply with Article 4 obligations; the substantive content of the NDC is equally relevant for assessing compliance. In other words, the discretion of Parties in preparing NDCs is limited. Parties’ NDCs must collectively be capable of achieving the 1.5°C goal, take into account the outcome of the Global Stocktake, and reflect the principle of CBDR/RC. In light of this Advisory Opinion, the 2035 NDC of South Korea should be established at a level that is higher than the global average reduction rate required to achieve the 1.5°C target and consistent with the country’s fair share of the carbon budget. With respect to domestic mitigation measures, the ICJ clarified that States must take proactive and reasonable measures to achieve their NDCs, including the establishment of legislative, administrative, and enforcement mechanisms, and ensure their effective operation. The Court’s analysis of the elements constituting the due diligence obligation — appropriate measures, scientific and technical information, relevant international rules and standards, and different national capabilities — provides useful guidance for shaping domestic mitigation policies. Accordingly, South Korea must reform its emissions trading system to ensure its effectiveness in achieving the NDC, rapidly increase its currently very low renewable energy share, and end the use of public finance for fossil fuel projects. The ICJ’s Advisory Opinion was delivered at a critical juncture when South Korea must decide on its long-term mitigation pathway for 2031–2049, including the 2035 NDC, following the Constitutional Court’s climate litigation decision in August 2024. The National Assembly and the Government must recognize that formulating and implementing NDCs and domestic mitigation measures that contribute effectively to achieving the 1.5°C goal is not only a constitutional obligation to protect fundamental rights from the climate crisis but also a legal duty under international law owed to all nations and to present and future generations facing existential threats from extreme weather events, sea-level rise, and ecosystem collapse.