Maritime transport plays a central role in global trade and remains a significant source of greenhouse gas emissions, yet its regulation has historically developed at the margins of international climate law. The sector has primarily been governed through technical instruments adopted within the framework of the International Maritime Organization, most notably the International Convention for the Prevention of Pollution from Ships (MARPOL). Although MARPOL, particularly its Annex VI, establishes important standards addressing air pollution and energy efficiency, it has often been perceived as a largely self-contained technical regime, insufficiently integrated into the broader body of international climate and environmental law. In this context, the recent advisory opinions of the International Court of Justice (ICJ) on the obligations of States in respect of climate change and of the International Tribunal for the Law of the Sea (ITLOS) on climate change and the marine environment mark a significant development with potential implications for the regulation of maritime transport. The present contribution examines the relevance of the advisory opinions of the International Court of Justice and the International Tribunal for the Law of the Sea for the climate regulation of maritime transport. It pursues three related objectives. First, it analyses the extent to which the ICJ advisory opinion clarifies the content of States’ climate-related obligations under international law, with particular regard to the duty of due diligence and the regulation of private activities. Second, it assesses the contribution of the ITLOS advisory opinion to the legal characterization of greenhouse gas emissions from maritime transport within the framework of the law of the sea. Third, it evaluates how the combined interpretative guidance provided by these opinions supports a reappraisal of MARPOL as part of the implementation of broader climate-related and marine environmental obligations. The paper adopts a doctrinal and systemic method of legal analysis, drawing on the principle of systemic integration as articulated by the International Law Commission in its work on the fragmentation of international law, according to which treaty interpretation must consider the broader normative context in which specific regimes operate (Koskenniemi, Fragmentation of International Law, para. 430). It examines the advisory opinions of the ICJ and ITLOS as authoritative interpretative statements and situates them within the normative architecture of international law, particularly in relation to the United Nations Convention on the Law of the Sea and the MARPOL regime. Rather than treating MARPOL as an isolated regulatory framework, the analysis considers its interaction with general principles of international law, including the duty of due diligence, the obligation to prevent significant environmental harm, and the protection of collective interests. This approach allows for an integrated assessment of sector-specific maritime regulation within the broader context of international climate and environmental law. The analysis demonstrates, first, that the ICJ advisory opinion provides significant clarification regarding the scope and content of States’ climate-related obligations, notably through the articulation of a duty of due diligence requiring States to adopt appropriate regulatory measures to limit greenhouse gas emissions, including those generated by private actors. As has been emphasized in the literature, these climate-related obligations are fundamentally obligations of due diligence, requiring States to take the measures necessary to prevent or minimize harmful pollution, including through environmental impact assessment, regulatory controls and the use of best available technology, and to control and reduce greenhouse gas emissions from sources likely to pollute the marine environment.” (Boyle, p. 88). The Court’s recognition of certain climate-related obligations as obligations erga omnes further underscores the collective dimension of climate protection and challenges the characterization of failures in regulating maritime emissions as matters of purely bilateral concern. This broader understanding of climate-related obligations is consistent with the approach adopted by the UN Human Rights Committee, which has acknowledged that the adverse effects of climate change may engage States’ positive obligations under international human rights law, including the duty to protect the right to life in contexts involving foreseeable climate-related harm (UN Human Rights Committee, Ioane Teitiota v. New Zealand, 2020). Second, the article shows that the ITLOS advisory opinion complements this general framework by explicitly linking climate change to the protection of the marine environment under the law of the sea. By qualifying anthropogenic greenhouse gas emissions as a form of marine pollution and reaffirming States’ obligations to prevent, reduce and control such pollution, ITLOS directly reinforces the applicability of international environmental obligations to maritime transport. This study contributes to the understanding of how the advisory opinions of the ICJ and ITLOS strengthen the legal foundations for the climate regulation of maritime transport and provide interpretative guidance for the application of MARPOL, particularly its Annex VI. By examining these opinions collectively, the study highlights their potential to reposition MARPOL within a more coherent system of international climate and environmental law, enhancing its role beyond a purely technical instrument toward an operational mechanism for the fulfilment of States’ climate-related and marine environmental obligations. In this regard, the consultative jurisprudence of the ICJ and ITLOS is shown to promote greater normative coherence within the international maritime regulatory regime and to offer clearer legal benchmarks for assessing State conduct in relation to the climate impacts of maritime transport.
Rodríguez et al. (Mon,) studied this question.