ICJ Advisory Opinion: What it Means for EIAs

After a particularly gloomy start to 2025 for people concerned about climate change and a growing wave of institutional backsliding, last week’s publication from the ICJ has provided a timely dose of optimism in categorically confirming States’ human rights obligations with regard to climate change. We bandy around terms like unprecedented far too easily, but this does feel like an unprecedented, albeit advisory opinion.

The advisory opinion provides authoritative guidance on two questions posed by the UN General Assembly:

(a) 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 emissions of greenhouse gasses (GHG) for States and for present and future generations?

(b) 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:

• (i) States, including, in particular, small island developing States, 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?
• (ii) Peoples and individuals of the present and future generations affected by the adverse effects of climate change?

The ruling states that a “clean, healthy, and sustainable environment” constitutes a human right. This interpretation moves the climate debate beyond the environmental or economic realm, positioning it as an issue of justice and fundamental rights.

The Center for International Environmental Law explains:

“In its long-awaited ruling on States’ legal obligations regarding climate change, the Court defined what justice means in the face of climate breakdown — ruling that countries must act with urgency, cooperate in good faith, and repair the damage already done— setting the stage for accountability and real action worldwide.” 

Although an advisory opinion, rather than binding legal ruling, it does appear to set a foundation for current and future court cases to be brought on historic and cumulative climate damages. As of June of this year, according to the most recent report from the Grantham Research Institute on Climate Change and the Environment, there were approximately 2,967 active climate change lawsuits in nearly 60 countries, with more than 226 new cases initiated in 2024 alone.

I attach a few links from which you can select your preferred level of detail: 1. short, 2. medium, or 3. long.

1. Türk hails landmark ICJ ruling affirming States’ human rights obligations with respect to climate change | OHCHR
2. DanishCenterHR5: This PDF from the Danish Centre for Human Rights is a very good capture of salient points (thank you, Gaby).
3. Summary of the Advisory Opinion of 23 July 2025

I would also recommend dipping into the UN’s own summary of the judgement. The myriad separate opinions from various judges at the end of the document (many saying it didn’t go far enough)are, for me, a useful guide to the strengths and (possible) weaknesses of the ruling.

And the significance for EIAs?

In establishing State’s legal responsibilities, deep within the text of the opinion is a section listing the responsibility of States to prevent transboundary environmental harm, which requires States to

“use all the means at [their] disposal in order to avoid activities which take place in [their] territory, or in any area under [their] jurisdiction, causing significant damage to the environment of another State”,

The main elements of the obligation of prevention in the context of protection of the climate system are (a) the environmental harm to be prevented and (b) due diligence as the required standard of conduct.

Para 298 — The Court is of the view that the risks posed by climate change have certain features that may affect the appropriateness of certain forms of environmental risk assessment. It may therefore be reasonable for States to conduct their assessments of the risk caused by GHG emissions by way of general procedures covering different forms of activities. Such general procedures do not exclude that possible specific climate-related effects must be assessed as part of EIAs at the level of proposed individual activities, e.g. for the purpose of assessing their possible downstream effects. While the Court is aware that the cumulative and diffuse nature of GHG emissions may involve some difficulty in risk assessment, it considers it important that all States provide for and conduct EIAs with respect to particularly significant proposed individual activities contributing to GHG emissions to be undertaken within their jurisdiction or control, on the basis of the best available science. Such specific climate-related assessments could identify previously unknown information about possibilities for reducing the quantity of GHG emissions by relevant proposed individual activities.

The ICJ advisory opinion emphasizes that Environmental Impact Assessments (EIAs) are a crucial legal tool at the national level for states to fulfil binding obligations to address climate risks. The Court underscores that states must conduct EIAs before undertaking any activities that could generate GHG or cause significant environmental harm, including transboundary or global impacts. This requirement is part of a stringent due diligence standard grounded in the “best available science” from the IPCC, obliging states to proactively identify, assess, and mitigate foreseeable climate risks within their jurisdiction.

Not to get too carried away, I also asked AI what this opinion means for EIAs, for which Perplexity concluded that:

‘the opinion transforms EIAs from mere procedural formalities into substantive, science-driven obligations.…. This elevates EIAs as a non-negotiable element in national climate governance, reinforcing states’ duty to act urgently and prevent foreseeable climate damage as part of their international legal obligations.

In summary, the ICJ advisory opinion stresses that EIAs are indispensable at the national level for operationalizing states’ legal duties to prevent climate change harm by applying rigorous, science-based risk assessment and mitigation frameworks.’

That is the AI summary of opinions thus far. Inevitably, the entire text will now be pored over and challenged by some, and likely ignored by others, but the direction of travel in environmental legal rulings seems clear: governments and corporations have a legal obligation to take GHG emissions and climate change effects seriously, or will face the consequences.

Coming just a few weeks ahead of the deadline for submitting National Determined Contributions (NDCs), ahead of COP30 in Brazil, there could well be some urgent additional drafting required by many countries yet to submit, and the same might also apply to the current renegotiation of the EU’s CSDDD framework.