ICJ Advisory Opinion on Climate Change: When Law and Politics Meet

By Elena Kosolapova, SDG Knowledge Hub

It is hard to think of an issue more politically charged than climate change. Presidential campaigns are won or lost depending on the candidates’ stance on global warming. The international political process seeking to solve the climate crisis is notorious for its contentious negotiations. Yet, following the recent International Court of Justice (ICJ) Advisory Opinion on climate change, climate action has now been classified as not merely a question of political will but as a legal imperative.

This Policy Brief reflects on how the ICJ Advisory Opinion navigated the intersection of law and politics, setting a clear legal benchmark that will inform climate action going forward.

In search of legal clarity

Frustrated with the slow pace of the climate talks, a youth-led campaign galvanized a political process, which in 2023 resulted in a UN General Assembly (UNGA) resolution requesting the International Court of Justice (ICJ) to clarify States’ climate change-related obligations and the legal consequences arising from their breach. The UNGA put the following questions before the Court:

What are the obligations of States under international law to ensure the protection of the climate system and other parts of the environment from anthropogenic greenhouse gas (GHG) emissions for States and for present and future generations?
What are the legal consequences under these obligations for States where they, by their acts and omissions, have caused significant harm to the climate system and other parts of the environment, with respect to: a) States, including small island developing States (SIDS), which, due to their geographical circumstances and level of development, are injured or specially affected by, or are particularly vulnerable to, the adverse effects of climate change? b) Peoples and individuals of the present and future generations affected by the adverse effects of climate change?

The UNGA’s request sought to demarcate the often-fluid boundary between what is legally required and what is politically expedient once and for all.

What the law is

In its 140-page Advisory Opinion, the ICJ provided legal clarity in a number of areas where political consensus proved elusive. It is no longer up for negotiation that:

the 1.5°C limit is a legally binding temperature goal under the Paris Agreement;
all States, especially the largest emitters of GHGs, must take ambitious mitigation measures in line with the best available science; and
States’ legal obligations emanate from multiple sources of law, not just the climate treaties, including customary duties to prevent transboundary harm and exercise precaution and due diligence by cutting GHG emissions and adapting to the adverse impacts of climate change.

Following the ICJ AO, the following questions have also been clarified:

the content of States’ nationally determined contributions (NDCs) under the Paris Agreement is not entirely up to parties’ discretion;
parties have to do their utmost to ensure their respective NDCs represent the highest possible ambition, with the exact standard depending on aspects such as the countries’ contribution to cumulative greenhouse gas (GHG) emissions and their level of development and national circumstances;
NDCs must, when taken together, be capable of achieving the temperature goal and purposes of the Paris Agreement; and
parties have an obligation to undertake best efforts to achieve their NDCs.

A State’s failure to take appropriate action to protect the climate system from GHG emissions – including those due to fossil fuel production, fossil fuel consumption, the granting of fossil fuel exploration licenses, or the provision of fossil fuel subsidies – may constitute an internationally wrongful act attributable to that State.

In addition, a State may be considered responsible for not taking the necessary regulatory and legislative measures to limit the emissions released by private actors under its jurisdiction or control.

Other significant findings include:

States parties to the Paris Agreement have obligations of adaptation and cooperation, including through technology and financial transfers, which must be performed in good faith.
The human right to a clean, healthy, and sustainable environment is essential for the enjoyment of other human rights.
Once a State is established, the disappearance of one of its constituent elements would not necessarily entail the loss of its statehood.

While the Court makes no pronouncement on the responsibility of individual States, noting that such responsibility would need to be assessed on a case-by-case basis, the Advisory Opinion lays out the available legal remedies, including non-repetition, restitution, and compensation.

Navigating the intersection of law and politics

Separating law from politics is just as important as leveraging the former to inform the latter.

Having clarified the obligations and consequences for their breach, the ICJ went a step further, expressing hope that “its conclusions will allow the law in inform and guide social and political action to address the ongoing climate crisis.” The Court recognized international law’s “important but ultimately limited role in resolving” climate change, which it described as “an existential problem of planetary proportions that imperils all forms of life and the very health of our planet.” It highlighted the need for contributions from law, science, economics, and other fields of knowledge, as well as “human will and wisdom – at the individual, social and political levels – to change our habits, comforts and current way of life in order to secure a future for ourselves and those who are yet to come.”

In his separate declaration, Judge Nolte underscored the potential of the Advisory Opinion to reinforce the political will and commitment of States “to tackle climate change through legally framed forms of political and administrative co-operation for which litigation plays a complementary role.”

In their joint declaration, Judges Bhandari and Cleveland emphasized that it is incumbent upon States to act – as well as on private actors in their jurisdiction – “who must re-evaluate and reform their policies to achieve the transformative change essential for the preservation of our shared future.” “Given the gravity of the crisis,” the Judges underscore the need for “all three branches of government – executive, legislative and judicial” to confront climate change in a coordinated manner.

This observation is significant for governments, the judiciary, and private actors alike. For example, under the political question doctrine, US federal courts have at times elected to exercise judicial restraint and refrained from weighing in on the merits of climate claims. Rooted in the notion of separation of powers, the doctrine has enabled defendants to argue that climate claims are non-justiciable because addressing the climate crisis is a political matter better left to the executive and legislative branches of government.

The ICJ has made it clear that climate action is not a political choice. While the Advisory Opinion is not binding on any court, its legal weight is such that it may help inform future determinations of what constitutes a political question, including at the national level.

At the international level, States have a duty to cooperate for the protection of the environment, and, as Judges Bhandari and Cleveland note, must do so “in a decisive manner that reflects the urgency of the moment and the need for collective global solutions.”

Politics of litigation

The Court has made important pronouncements on what States’ legal obligations are with respect to climate change. It has also clarified that “any State may invoke the responsibility of those not in compliance with international law to enforce obligations owed to all through courts.” Law – and indeed litigation – are powerful tools but, as Judge Nolte cautioned, we mustn’t forget that if the Advisory Opinion were to be seen “as having identified a way for States that are not satisfied with the political process under the Paris Agreement to achieve their goals through litigation, including through claims for compensation, unintended effects are likely to follow.” For all its faults, the collective process is valuable. It is also “fragile, and the stakes are high.”

* * *

This Policy Brief is part of a project that seeks to raise awareness and build momentum and knowledge around the ICJ advisory opinion on obligations of States in respect of climate change and to promote a better understanding of the implications of the advisory opinion among sustainable development decision makers.