Obligations of States in respect of Climate Change was an advisory proceeding before the International Court of Justice (ICJ), the United Nations’ main judicial organ. The Court was asked by the General Assembly to clarify what international law requires states to do about climate change, and what legal consequences follow when states breach those obligations. The Court delivered its unanimous advisory opinion on 23 July 2025, clarifying that states’ climate obligations arise not only from climate treaties, but also from customary international law and other applicable international legal rules. 

International participation in the proceedings was exceptionally broad, with 96 states and 11 international organizations giving oral statements. Furthermore, the Court works in English and French. Translation was thus structurally embedded in the process from the start.

For legal translators, the ICJ opinion illustrates the difficulty of making laws, rules, agreements, and legal obligations intelligible across languages without changing their scope, thresholds or consequences. Terms such as “due diligence,” “significant harm,” “customary international law,” “state responsibility” and “reparation” played important roles in the proceeding. 

Their translation was not a matter of merely replacing a word in one language by its equivalent in another; rather, it was a question of preserving their function within a legal argument. Specifically, in climate litigation, a translation must convey whether a term identifies a source of law, a standard of conduct, a threshold of harm, the consequences of breach or a remedy.

1. “Due diligence”: translating a standard of conduct

In this proceeding, “due diligence” describes the measures states must take to fulfil their obligation to prevent significant environmental harm. The Court characterized the applicable climate standard as stringent, requiring states to employ all means reasonably available to prevent harm as far as possible.

The key translation challenge is to preserve the distinction between an obligation of conduct and a guarantee of a particular outcome. Due diligence is neither a promise that no climate harm will occur nor a loose invitation to make some effort. Its content depends on what is reasonably required in the circumstances, informed by factors including the risk, scientific knowledge, and the state’s capabilities.

In climate litigation, this distinction directs attention to what a government actually did: whether it adopted and enforced appropriate regulatory measures, assessed risks and acted on available knowledge. The Court specifically connected due diligence with regulatory mechanisms designed to achieve deep, rapid, and sustained reductions in greenhouse gas emissions.

For a translator, the practical implication is to preserve not just the term but its surrounding qualifiers. Omitting “stringent,” weakening “must” into “should,” or translating the obligation as a guaranteed result would alter the legal standard.

2. “Significant harm”: translating a threshold

This expression concerns the threshold relevant to the duty to prevent environmental harm, including harm to the climate system. The Court stated that determining whether significant harm has occurred requires consideration of the best available scientific evidence.

The difficulty is that “significant” looks like an ordinary descriptive adjective but performs a legal function. A translation should not casually substitute “catastrophic,” “irreversible” or “minor”, as each adjective would suggest a different threshold.

The climate context also changes how the threshold operates. The Court recognized that a risk of significant harm can arise from the cumulative effects of activities undertaken by different states, even where identifying an individual state’s precise share is difficult. The concept therefore cannot be reduced to a single event or a single source of emissions. 

A further distinction must survive translation: significant harm is not automatically proof of a breach. Because prevention operates through due diligence, assessing compliance requires examining the state’s conduct, not simply observing that damage occurred. That distinction also appeared in the written submissions to the Court.

3. “Reparation”: translating an overarching remedy

English reparation and French réparation are closely related, but their similarity can conceal an important distinction: reparation is broader than financial compensation.

The Court explained that full reparation may take the form of restitution, compensation or satisfaction, or a combination of them. The corresponding French terms are restitution, indemnisation and satisfaction. 

A translation that consistently renders “reparation” as “compensation” would therefore narrow the meaning. It would replace the overarching remedial category with only one of its possible forms.

In the climate proceeding, the Court also distinguished establishing responsibility from establishing a claim for reparation. Causation of damage is not a general requirement for determining state responsibility, but a causal connection between wrongful conduct and injury is relevant when reparation is sought.

This distinction matters in litigation: a finding that a state breached an obligation does not, by itself, establish how much compensation it must pay or to whom. The translation must preserve the conditions linking the breach to the claimed injury.

4. “Customary international law”: translating a source of obligation

In the climate opinion, the Court identified customary obligations to prevent significant environmental harm and cooperate in protecting the climate system, alongside obligations under treaties.

The translation must preserve “customary international law” as a legal category, not paraphrase it as customary behaviour, diplomatic practice or voluntary convention. Such wording would obscure the point that the Court was identifying legal obligations.

Its significance in this proceeding is the reach of those obligations beyond particular treaty memberships. The Court’s analysis did not treat climate treaties as the exclusive source of climate duties.

For multilingual drafting, that means keeping the source of each obligation clear. A duty arising under the Paris Agreement should not be presented as interchangeable with a duty arising under customary international law, even where the two support related conduct.

5. “State responsibility”: translating the consequences of breach

Here, “responsibility” is a technical legal concept, not merely political accountability or a moral expectation that governments behave responsibly.

The Court confirmed that the general rules of state responsibility apply to climate change. These rules address internationally wrongful acts and their consequences, including cessation, non-repetition where appropriate and reparation when the relevant conditions are satisfied.

A translation must also preserve the distinction between emissions and wrongful conduct. As the Court’s French press release explains, the wrongful act is not emissions in themselves, but acts or omissions causing significant harm in violation of a state’s international obligations.

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The Obligations of States in respect of Climate Change proceeding is a good example of why multilingual legal drafting is a substantive rather than a cosmetic issue: it needs to make the same legal distinctions available across languages without silently widening or narrowing them.