A key takeaway of the Worldwide Court docket of Justice’s (ICJ or Court docket) 23 July 2025 advisory opinion on the Obligations of States in Respect of Local weather Change is that the local weather treaties don’t displace different guidelines and rules of worldwide regulation in responding to local weather change (para 170), and that the ‘total corpus of worldwide regulation’ is probably related (para 98). In that interpretive gentle, the Court docket got here to the view {that a} State’s failure to take applicable measures to guard the local weather system from greenhouse gases (GHGs) applies in respect of manufacturing of fossil fuels, not simply consumption (para 427). With out the complete corpus of worldwide regulation being probably related, a a lot narrower reply could have been given.
Problems with relevant regulation and associated interpretative problems with whether or not the Paris Settlement was lex specialis or to be interpreted in accordance with the precept of systemic integration have been entrance and central each within the deliberate design of the Query requested of the ICJ by the UN Common Meeting and in States’ oral submissions (see e.g. the US and Saudi Arabia).
The explanation a solution on integration is helpful is that it unlocks a raft of relevant regulation in respect of local weather change. Within the following, I’ll concentrate on the Court docket’s affirmation of systemic integration as an interpretative method and its use of cross-citation as a type of institutional integration. In taking an integrative method, the Court docket has made worldwide regulation extra coherent.
The Query
The Query requested about: (A) obligations of States underneath worldwide regulation to make sure safety of the local weather system from anthropogenic emissions of GHGs; and (B) authorized penalties underneath these obligations the place States have prompted important hurt to the local weather system.
The chapeau to the Query referred the Court docket to have ‘explicit regard’ to a particular checklist of sources: the UN Constitution, the ICCPR and ICESCR human rights treaties, the UNFCCC, the Paris Settlement, and UNCLOS in addition to quite a lot of customary rules together with due diligence, prevention, and the responsibility to guard and protect the marine surroundings.
The Court docket’s resolution on relevant regulation
Interpretation of the query
The framing of the chapeau didn’t bind the Court docket as to relevant regulation. Nonetheless, the Query’s chapeau was meant to information the Court docket, and did in actual fact have that operate (para 99). The Court docket interpreted the Query as broadly as was meant by the group of co-sponsoring States. Within the Court docket’s phrases, the ‘unqualified reference to obligations “underneath worldwide regulation” signifies the intention of the Common Meeting to hunt the Court docket’s opinion … [on] all the corpus of worldwide regulation” and, critically, ‘to not restrict the Court docket’s reply to any explicit supply or space of worldwide regulation’ (para 98). The Court docket interpreted the phrase ‘explicit regard to’ as a request to determine ‘essentially the most immediately related relevant regulation’ (para 114).
Relevant regulation: Straight related and guiding rules
The Court docket decided there to be two classes of relevant regulation. This categorisation train illustrates the vary of areas of regulation that have been utilized by the Court docket.
The Court docket labeled some guidelines as ‘immediately related’ (paras 115-140) and others as ‘guiding rules for the interpretation and utility of essentially the most immediately related guidelines’ (paras 141-161). By and huge, the principles that the Court docket thought-about to be immediately related are the sources set out within the Query’s chapeau—local weather/environmental, human rights and regulation of the ocean. As well as, the Court docket added different environmental treaties (paras 125-129) and the customary responsibility to cooperate to guard the surroundings (paras 140-142) to its class of immediately related legal guidelines. The Court docket additionally constructed on different normative notions within the Paris Settlement, such because the Article 4.1 requirement that mitigation be primarily based on the ‘greatest obtainable science’ (paras 74, 224). In its class of guiding rules, the Court docket included sustainable improvement, widespread however differentiated tasks, fairness (together with intergenerational fairness), and the precautionary method.
This goes past what the minimal that the Court docket may have discovered. Final 12 months, Rajamani characterised a few of these guiding rules because the ‘normative surroundings’ of the Paris Settlement however probably falling wanting bindingness. The ICJ’s opinion affirms that each one of these listed are binding, and affirmed the substantive content material of the phrase ‘greatest obtainable science’. In doing so, it did precisely what Rajamani had argued: the Court docket ‘constrain[ed] unbridled subjective [NDCs]’ (for commentary on the Court docket’s clarification of mitigation obligations, see Voigt).
Figuring out there to be two classes of relevant regulation begs the query: how do these legal guidelines work together? I supply a solution to the meta-question: what guidelines govern how these guidelines work together?
Rejecting the lex specialis argument
Whether or not the local weather treaties represent lex specialis was contested by States; the bulk steered they don’t (para 163). The lex specialis precept requires there to be an precise inconsistency between two provisions, however the Court docket was unable to search out any precise inconsistency (para 167-168). Furthermore, States have been conscious of the ‘normative context’ of the local weather treaties and didn’t select to displace different guidelines when making negotiating the local weather guidelines (para 170). In rejecting the lex specialis argument, the Court docket paved the best way for accepting one that will radically shift the scope of relevant regulation: systemic integration.
Systemic integration in local weather litigation
Systemic integration is a precept of interpretation underneath Article 31(3)(c) of the Vienna Conference on the Regulation of Treaties: treaty interpreters (such because the ICJ) should take account of ‘any related guidelines of worldwide regulation relevant within the relations between the events’. Typically heralded as an answer to fragmentation, the precept of systemic integration requires judges to ‘mak[e] positive that the end result is linked to the authorized surroundings’. The foundational thought is that assorted guidelines of worldwide regulation ‘take their that means from their connections to one another as a set of interlocking norms which might be half of a bigger system’ (McLachlan).
The Court docket affirmed the ‘typically recognised precept’ that ‘when a number of guidelines bear on a single subject, they need to, to the extent potential, be interpreted in order to provide rise to a single set of suitable obligations’ (165, citing the ILC).
Utilized, the Court docket took the view that ‘worldwide human rights regulation, the local weather change treaties and different related environmental treaties, in addition to related obligations underneath customary worldwide regulation, inform one another’ (para 404, emphasis added). In different phrases, States should take their obligations underneath every space of regulation into consideration when implementing their obligations in different areas of regulation.
Implications
In doing so, the ICJ went far additional by way of systemic integration than the ITLOS advisory opinion on local weather change (see e.g. ITLOS’ cursory reference to human rights regulation, para 66). Some criticised ITLOS’s opinion as a ‘missed alternative’ to completely combine these areas of relevant regulation. We’d have anticipated ITLOS to be extra reticent, given its core mandate is to adjudicate disputes arising from UNCLOS (however see Article 293 UNCLOS, which empowers ITLOS to use ‘this Conference and different guidelines of worldwide regulation not incompatible’). Nonetheless, the ICJ has actually picked up the baton, and brought the chance to synthesise all three areas: local weather/environmental regulation, regulation of the ocean, and human rights, in addition to worldwide humanitarian regulation and worldwide funding regulation (Declaration Cleveland).
Failure to affirm a systemic integrative interpretation of the relevant regulation would have had adverse penalties. As Voigt factors out, such a place may have resulted within the Court docket establishing different obligations in respect of local weather change motion, additional fragmenting the corpus of worldwide regulation and probably undermining the relevance of these components of the worldwide local weather treaty regime which might be legally binding, in addition to probably derailing political negotiations on the annual Conferences of Events of the Paris Settlement. As an alternative, what we noticed was a strengthening of the Paris Settlement obligations, buttressed by obligations from different areas of regulation, corresponding to human rights regulation and regulation of the ocean.
Arguably, the Court docket didn’t go far sufficient. Though the ICJ cited the Inter-American Court docket’s (IACtHR) advisory opinion revealed 3 July on local weather change (para 385), the Court docket as an entire failed to interact with it. The ICJ’s opinion was revealed simply twenty days later, and we will assume it was largely agreed (it was unanimous). As an alternative, we see solely two judges writing individually mentioning it, once more treating it comparatively frivolously (see Sep Op Charlesworth and Sep Op Aurescu). Given the distinctiveness of the present scenario of the 4 advisory opinions on local weather change in a brief time frame (ITLOS, IACtHR, ICJ and the African Court docket on Human and Individuals’s Rights (nonetheless pending)), and that the ICJ is the one of these courts with common jurisdiction, the ICJ may and maybe ought to have delayed its opinion by a brief interval to extra absolutely handle the IACtHR opinion in the identical approach it fulsomely addressed the ITLOS advisory opinion.
Institutional integration
Along with systemic integration, one other type of integration is in motion: cross-citation or inter-judicial dialogue as institutional integration. Little consideration has been paid to this within the local weather literature (however see right here), though some students have paid consideration to it within the human rights regulation extra typically (right here) and it has been advocated as a response to fragmentation. See for instance, Benvenisti and Downs have posited that cross-citation ‘can operate as a sort of world good’, ‘probably accelerating the evolution of a extra coherent worldwide authorized system’; extra lately, ILC Particular Rapporteur Mr Jallo argues that reliance on different judicial selections underneath Article 38(1)(d) of the ICJ Statute ‘supplies stability’ and ‘could present an answer to sure … adverse penalties of … fragmentation’ (Third report on subsidiary means). Taking the argument a step additional, Andenas and Leiss argue that Article 38(1)(d) of the ICJ Statute is a ‘logical corollary’ to the precept of substantive integration, obliging courts to take into consideration different related judicial selections. Leaving apart whether or not they’re proper that this creates an obligation, I undertake their time period for this phenomenon: ‘institutional integration’.
I counsel the ICJ’s advisory opinion displays appreciable institutional integration, citing different local weather circumstances and arguably treating them as a ‘subsidiary supply’ of regulation underneath Article 38(1)(d).
For instance, the ICJ relied on ITLOS’ advisory opinion (paras 337-338). The ICJ endorsed ITLOS’ findings that many provisions of UNCLOS represent obligations of States in respect of local weather change. To take only one instance, the discovering that anthropogenic GHGs pollute the marine surroundings inside the that means of UNCLOS (ITLOS advisory opinion, paras 161-179, ICJ advisory opinion, para 340; and see others ICJ advisory opinion paras 340-353).
In respect of human rights jurisprudence, the ICJ took an excellent wider response, citing regional courts in addition to the UN human rights treaty our bodies (para 144). Specifically, the ICJ additionally endorsed core jurisprudence of the UN human rights treaty our bodies, such because the Human Rights Committee’s findings in Teitiota v New Zealand that environmental degradation can result in a violation of the suitable to life and may give rise to non-refoulement obligations (ICJ advisory opinion, paras 377-378, citing Teititoa, paras 9.5, 9.11), and the findings in Billy v Australia that States’ ‘failure to implement well timed and ample adaptation measures to deal with the adversarial impacts of local weather change could violate the suitable to privateness, household and residential’ (ICJ advisory opinion, paras 381, citing Billy, paras 8.9-8.12). The ICJ additionally cited, however didn’t explicitly endorse explicit findings of, regional human rights-based local weather litigation (para 385).
These findings in different worldwide courts are a part of a concerted effort of strategic litigation to make use of human rights regulation to fill the hole created by largely non-binding local weather treaties. In its advisory opinion, the ICJ used them as a subsidiary supply to interpret ‘immediately related’ sources of regulation (corresponding to UNCLOS and the human rights treaties).
Implications
Advisory opinions are after all non-binding. That doesn’t imply they’re with out significance. A lot of the anticipated significance reliance on the advisory opinion in different litigation, treating the advisory opinion as a persuasive authorized authority that different courts can reference to help them making related findings. The ICJ has itself taken and due to this fact given credence to such an method. In different phrases, we count on to see not simply extra local weather litigation, however litigation that tends in direction of institutional integration. That is possible in each different worldwide and regional courts in addition to in home courts. Such motion aids within the evolution of authorized norms, rules and requirements and builds normative coherence.
Conclusion
As Feria Tinta suggests, there has by no means been a ‘larger want for coherence’ than in respect of responding to the local weather disaster, for these points are existential. Systemic and institutional integration usually are not a panacea. However use of those synthesising methods does imply that the regulation is a extra convincing instrument to deal with the challenges we face. Within the phrases of the ICJ, ‘the purpose right here is to realize the required readability and the important consistency of worldwide regulation, in addition to authorized safety’ (para 338, citing Diallo para 66). Now that now we have a transparent and constant authoritative assertion of worldwide regulation about obligations in respect of local weather change, worldwide regulation might be extra persuasively used as one of many guiding instruments, alongside different ‘fields of human information’ to ‘inform and information social and political motion to deal with the continued local weather disaster’ (ICJ advisory opinion, para 456).
Rebecca McMenamin, LLM (Cantab), LLB/BA (Wellington), is a PhD Candidate on the College of Vienna, writing about human rights-based local weather litigation and worldwide regulation.
