Nationally Determined Contributions and Discretion: Five lessons from the International Court of Justice
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Africa’s contribution to historical greenhouse gas emissions (“GHGs”) is relatively nominal, yet it is among the regions most vulnerable to the impacts of climate change. Across the continent, droughts, floods, food insecurity, water stress, biodiversity loss, and displacement are intensifying, placing growing pressure on governments to respond through law and policy.
Central to that response are nationally determined contributions (“NDCs”) under the Paris Agreement, the primary mechanism under international law through which States communicate how they intend to mitigate GHGs and adapt to climate change.
Indeed, since stepping onto the global climate governance stage in 2015, the Paris Agreement has received mixed responses. Nearly every African State is a signatory to the Paris Agreement and many have submitted revised NDCs due in 2025. Voigt has described the Paris Agreement as “the best hope for an effective solution on climate change”, while critics have dismissed it as weak or “non-binding”. Critics often focus on States being permitted to determine their own GHG reduction targets and measures to adapt to the impacts of climate change through the NDC mechanism with five-year NDC cycles.
The seminal Advisory Opinion Obligations of States in respect of Climate Change of 23 July 2025 (“ICJ AO”) of the International Court of Justice (“ICJ”) is a powerful response to critics. Several African States participated actively in the proceedings before the ICJ and the outcome carries important implications for climate governance on the continent, particularly regarding the legal status, content, and implementation of NDCs. In what follows, we identify five lessons emerging from the ICJ AO regarding the nature and content of NDCs, highlighting their implications for African States in particular.
Lesson 1: Communicating NDCs is not optional
Scholars have long emphasised that the Paris Agreement is an international environmental law treaty containing a calibrated mix of hard, soft, and non-obligations, and that its legal character or normative force is to be understood as provision-specific. The ICJ AO crystallised the legal consequences of Articles 4(2) and 4(9) of the Paris Agreement, finding that the obligation to prepare, communicate and maintain successive NDCs is “procedural in nature and an obligation of result”. While an obligation of conduct requires a Party to act with diligence and take reasonable steps toward a goal without guaranteeing a particular outcome, an obligation of result demands that a specific, defined outcome be achieved. The ICJ AO clarified that State Parties’ duties relating to the preparation, communication and maintenance of an NDC every five years are binding, rather than voluntary. A State’s failure to develop an NDC “would constitute a breach” of the Paris Agreement. Worringly, many African States have reportedly not yet issued revised NDCs due in 2025 and are accordingly in breach of this obligation of result.
Lesson 2: COP decisions can matter legally
The ICJ AO confirmed that decisions of the Conference of the Parties (“COP”) of the United Nations Framework Convention on Climate Change (“the UNFCCC”), the parent treaty from which the Paris Agreement emerged, and of the meetings of the Parties to the Paris Agreement (referred to as the “CMA”) are not merely “political” and are relevant to legal obligations, since they may generate a legally binding obligation. Decision 1/CP.21 (adopting the Paris Agreement) is illustrative. While not every paragraph of a Decision is automatically “hard law”, they can become legally binding, highlighting the importance of African States making their voices heard in COP and CMA decision-making.
Lesson 3: Discretion over NDC content is real, but not unfettered
The Paris Agreement leaves each Party significant policy space to determine how it will fulfil its obligations to prepare, communicate and maintain successive NDCs. For instance, it does not prescribe national emissions caps. But States’ discretion is not unfettered. First, the ICJ opined that: “All NDCs … must, when taken together, be capable of realizing the objectives of the Agreement … set out in Article 2”. Second, Article 4(3)’s “highest possible ambition” and “progression” expectations of NDCs were interpreted through the lens of the customary duty to prevent significant environmental harm, which introduces due diligence constraints on how Parties exercise their discretion. Thus, the adequacy of an African State’s NDCs can be assessed with reference to the overall objectives of the Paris Agreement and whether it represents progression rather than regression and gives effect to the customary duty to prevent significant environmental harm through due diligence measures (e.g. climate change impact assessments).
The Court’s move, supported by leading scholarship, was to link ambition in NDCs to adequacy. It observed that “highest possible ambition” in relation to a State’s NDC means that the content of the NDC “must … be capable of making an adequate contribution” to achieving the temperature goal, which the Court read as “below 1.5°C” as the Agreement’s primary temperature goal. The Court anchored this view in various procedural tools of the Paris Agreement: NDCs should be informed by the global stocktake outcomes (Article 14, as expressly reflected in Article 4(9)) and transparency and accounting requirements (Articles 4(8) and 4(13)).
Lesson 4: Differentiated assessment, not differentiated escape
The imposition of standards of adequacy and ambition in relation to the content of NDCs does not ignore the common but differentiated responsibilities and respective capabilities principle (“CBDR-RC”). The ICJ AO noted that when assessing NDCs against these standards, a variable approach must be adopted “depending, inter alia, on historical contributions to cumulative GHG emissions, and the level of development and national circumstances”.
The Court added an explicit conceptual bridge between due diligence and CBDR-RC: that discretion is structured by fairness, but fairness is not a licence for inadequacy. In other words, African States must appreciate that while their relatively nominal historical contribution to GHGs matters (since the Paris Agreement’s standards are context-sensitive), the standards remain stringent, not anything goes.
Lesson 5: On implementation
Finally, on implementing NDCs, the ICJ AO distinguished between what Parties must do domestically and what they must achieve. Article 4(2)’s procedural duties are obligations of result (communicate/account/register). But Article 4(4)’s duty to “pursue domestic mitigation measures” is an obligation of conduct. African States, therefore, need not guarantee that they will meet their NDCs but must use “best efforts” and exercise due diligence, including by regulating private actor such as multinational corporations operating within their borders. Further, because climate change poses a serious threat, the applicable due diligence standard is “stringent”. African States must proceed on the basis that even conduct obligations can be legally demanding given that the benchmark is “stringent” due diligence, informed by an evolving body of climate science and global stocktake outcomes that increasingly supply concrete directional signals for the content of NDCs and how they are to be implemented. For example, the 2023 CMA draft outcome text called for transitioning away from fossil fuels in energy systems “so as to achieve net zero by 2050 in keeping with the science”. The objective is clear and shapes the conduct expected to achieve it.
Conclusion
Overall, the Paris Agreement should be understood as an instrument requiring States to exercise disciplined discretion in response to the realities of an increasingly warming planet. The obligation related to communicating, accounting for, and registering NDCs is legally binding, and in key respects an obligation of result. The content of NDCs remains discretionary and nationally determined, but not normatively untethered or entirely fluid. Due diligence, Article 2’s objectives, transparency and accountability, and global stocktake outcomes constrain the exercise of States’ discretion, with a “stringent” standard calibrated through CBDR-RC and national circumstances. These are, in turn, to be informed by climate science.
The Paris Agreement contains both obligations of conduct and obligations of result, neither of which are toothless. They are increasingly justiciable because the ICJ has provided a way to translate “national determination” into reviewable standards of due diligence, adequacy, and progression, whether in domestic, regional or international courts, or other fora. Moreover, the distinction between obligations of conduct and result is not a “strict one”: the objective of keeping the increase in Earth’s surface temperature to below 1.5°C since pre-industrial levels remains ever-present. African States, therefore, must exercise disciplined discretion to ensure that the climate system, a critical component of Earth’s life support system on which all of humanity depends for its survival, does not collapse.
