For a very long time, the duty to co-operate occupied an ambiguous place in worldwide legislation. It appeared in numerous treaty regimes and institutional contexts, but it was seldom recognised as an autonomous, self-standing obligation, i.e., as a common responsibility of customary nature, underpinning the assorted authorized regimes, and as a real authorized obligation in its personal proper. One may due to this fact have anticipated that the current advisory opinions delivered by the Worldwide Court docket of Justice (‘ICJ’ or ‘Court docket’), most notably the 2024 opinion on Authorized Penalties arising from the Insurance policies and Practices of Israel within the Occupied Palestinian Territory, together with East Jerusalem (‘Authorized Penalties advisory opinion’), the 2025 opinion on Obligations of States in respect of Local weather Change (‘Local weather Change advisory opinion’), and the 2025 opinion on Obligations of Israel in relation to the Presence and Actions of the United Nations, Different Worldwide Organizations and Third States in and in relation to the Occupied Palestinian Territory (‘UNRWA advisory opinion’), would supply the normative clarification lengthy missing.
This publish thus examines how the Court docket has articulated the responsibility to co-operate throughout its current advisory jurisprudence and demonstrates that, slightly than resolving the paradox, the Court docket’s reasoning throughout these choices has created a extra complicated and fewer coherent image. It first analyses the completely different fashions of co-operation rising from the ICJ’s opinions, earlier than turning to the implications of this variability for the scope, content material, and sensible operability of the responsibility.
Co-operation within the ICJ’s Current Advisory Jurisprudence
In its 2024 Authorized Penalties opinion, the Court docket discovered that every one States should co-operate with the UN in bringing Israel’s unlawful presence within the occupied Palestinian territory to an finish and securing the total realisation of the Palestinian folks’s proper to self-determination [p. 74, para. 275]. This reworked what was previously conceived within the 2004 advisory opinion on the Authorized Penalties of the Development of a Wall within the Occupied Palestinian Territory (‘2004 Wall advisory opinion’) as a set of destructive duties right into a collective [p. 196, para. 146], affirmative obligation of erga omnes character. Notably, nonetheless, whereas the Court docket had recognized the fitting of self-determination as a peremptory norm of worldwide legislation, it didn’t floor the responsibility to co-operate explicitly within the jus cogens character of that norm [pp. 65-6, para. 233]. As a substitute, it relied on the erga omnes nature of the obligations breached, recalling that such obligations are ‘the priority of all States’ and that, ‘in view of the significance of the rights concerned, all States might be held to have a authorized curiosity of their safety’ [p. 74, para. 274]. This reasoning is doubtlessly complicated, because it seems to connect to the erga omnes character of the obligations the very penalties—non-recognition, non-assistance, and co-operation—that the Worldwide Legislation Fee (‘ILC’) has persistently related to severe breaches of jus cogens underneath Articles 40 and 41 of the ILC Draft Articles on State Duty [p. 112, paras. 1-5; cf. also ILC Draft conclusions on identification and legal consequences of peremptory norms of general international law (jus cogens), p. 70, para. 1]. By grounding the responsibility to co-operate within the erga omnes dimension slightly than explicitly within the peremptory character of the norm, the Court docket dangers conflating analytically distinct classes [cf. here and here; for a different assessment, cf. here]. This ambiguity turns into extra obvious when the Court docket’s reasoning is located in opposition to the ILC’s personal cautious strategy. The ILC expressly acknowledged that ‘it might be open to query whether or not common worldwide legislation at current prescribes a constructive responsibility of cooperation’, observing that paragraph 1 of Article 41 might replicate a component of progressive improvement [p. 114, para. 3]. On the identical time, the ILC emphasised that co-operation—particularly inside the framework of worldwide organisations—is already practised in response to the gravest breaches of worldwide legislation [ibid.]. This cautious formulation mirrored the ILC’s reliance on a normative evaluation of rising follow, pointing to adequate materials to assist the progressive consolidation of the duty—an strategy that has since developed. In its 2022 Draft Conclusions on the identification and authorized penalties of peremptory norms of common worldwide legislation (jus cogens), the Fee noticed that ‘obligation to cooperate to convey to an finish severe breaches of obligations arising underneath peremptory norms of common worldwide legislation (jus cogens) is now acknowledged underneath worldwide legislation’ [pp. 70-1, para. 2]. In opposition to this background, the Court docket’s strategy in 2024 marks a big departure from its place within the 2004 Wall advisory opinion, the place it intentionally confined itself to collective duties of non-recognition and non-assistance [p. 196, para. 146]. Thus, the Court docket mirrored the identical warning acknowledged by the ILC. Against this, within the 2024 Authorized Penalties opinion, the Court docket employs unequivocally deontic language, stating that ‘all States should co-operate’ [emphasis added]. This formulation suggests a shift within the Court docket’s articulation of collective accountability in direction of a extra assertive framing of co-operation as a constructive requirement. In doing so, the Court docket’s reasoning more and more mirrors the construction of the ILC’s framework on collective responses to severe breaches, although the ICJ invokes a distinct doctrinal set off.
The Local weather Change advisory opinion is notable for one of many Court docket’s clearest acknowledgements of a customary responsibility to co-operate, albeit in a fastidiously circumscribed type. The ICJ observes that worldwide co-operation is indispensable within the subject of local weather change and that ‘the customary responsibility to co-operate for the safety of the atmosphere is mirrored in a number of provisions of the local weather change treaties’ [p. 70, para. 215]. On the identical time, the Court docket provides that ‘State co-operation is a paramount precept in fixing international issues’ [p. 82, para. 261]. Nonetheless, this responsibility is introduced not as a common obligation of worldwide legislation, however slightly as a sector-specific rule grounded within the explicit pursuits at stake, i.e., erga omnes, thereby reflecting the Court docket’s warning in recognizing a customary responsibility solely the place State follow and opinio juris are particularly dense, whereas avoiding any declare of a common responsibility to co-operate. Accordingly, whereas the Court docket’s language might sign openness to a extra substantial position for co-operation in addressing international challenges, it finally falls wanting recognizing a common obligation underneath worldwide customary legislation. This restrained strategy stands in sharp distinction to the Court docket’s reasoning in its 2024 Authorized Penalties advisory opinion. If the Court docket‘s reasoning within the Authorized Penalties opinion—attaching the responsibility to co-operation to the erga omnes character of the breach—have been taken at face worth, the Court docket’s identification of erga omnes obligations within the Local weather Change advisory opinion ought to logically have entailed a corresponding responsibility to co-operate [cf. Declaration of Judge Tladi, p. 10, paras. 36-7]. But, the Court docket didn’t articulate any such consequence in that context, nor does it clarify why the responsibility to co-operate doesn’t come up [ibid.]. The result’s a jurisprudence wherein the triggering circumstances and authorized foundation of the responsibility to co-operate stay unsure, oscillating between a binding consequence of erga omnes breaches and a context-specific precept confined to explicit regulatory domains [ibid.].
In its 2025 UNRWA advisory opinion, the Court docket grounded the responsibility to co-operate in Article 2(5) of the UN Constitution, holding that ‘Israel might not hinder the features of the United Nations and should present each help in any motion taken by the Group’ [p. 55, para. 179]. This formulation expressly combines a destructive obligation (non-obstruction) with a constructive obligation (the availability of ‘each help in any motion’), reflecting the explicit wording of Article 2(5) itself [p. 54, para. 172]. On the stage of precept, the Court docket thus seems to endorse a broad and absolute responsibility of co-operation with UN organs and businesses. Nonetheless, the Court docket doesn’t translate this abstractly broad obligation into concrete operational necessities. Owing to the wording of the UN Basic Meeting’s request, the Court docket confined its evaluation to the obligations of Israel alone, with out addressing the corresponding duties of UN member States extra usually, and with out figuring out whether or not Israel had in reality breached its obligations [p. 33, para. 77]. In consequence, the opinion leaves unresolved how Constitution-based duties of co-operation relate to a broader framework of collective accountability relevant to severe breaches of jus cogens. This silence is very hanging when contrasted with the strategy taken by the ILC, which expressly addressed the connection between institutional co-operation and severe breaches of peremptory norms. The ILC discovered that, ‘the place a global group has the discretion to behave, the duty to cooperate imposes an obligation on the members of that worldwide group to behave with a view to the group exercising that discretion in a way to convey to an finish the breach of a peremptory norm of common worldwide legislation (jus cogens)’ [pp. 75-6, para. 11; emphasis added]. This omission might replicate a reluctance on the a part of the Court docket to articulate the total systemic implications of Constitution-based co-operation for collective responses to jus cogens violations.
Scope and Content material of the Responsibility to Co-operate
The Court docket’s jurisprudence additional confirms that the scope and content material of the responsibility to co-operate differ considerably relying on their authorized foundation. The divergent scope and content material of the responsibility to co-operate throughout these contexts might arguably not be unintentional and replicate the distinct authorized bases and features from which the duty arises. Nonetheless, this useful differentiation is accompanied by a pronounced asymmetry in normative readability, significantly in circumstances the place co-operation is grounded in severe violations of jus cogens and in constitutional obligations of UN membership.
The place co-operation is invoked in response to an internationally wrongful act, as within the 2024 Authorized Penalties opinion, the responsibility is conceived primarily as an enforcement-oriented collective response geared toward bringing an illegal scenario to an finish. But, exactly due to the gravity of the norms at concern, the absence of articulated requirements is very problematic. The Court docket elevates co-operation to a binding, affirmative obligation incumbent upon all States, whereas on the identical time failing to specify its modalities, limits, or evaluative standards. In contrast to within the local weather change context, no benchmark—equivalent to due diligence, reasonableness, or proportionality—is obtainable in opposition to which State conduct is perhaps assessed. The result’s an obligation that’s normatively maximalist however operationally opaque, elevating doubts as as to if States are anticipated to take concrete constructive measures, to behave by means of particular institutional channels, or merely to assist collective processes in a common sense.
A comparable lack of normative readability characterizes the responsibility to co-operate derived from institutional obligations underneath the UN Constitution, as illustrated by the UNRWA advisory opinion. Whereas the Court docket grounds the duty firmly in Constitution provisions, it doesn’t translate this abstractly broad obligation into concrete operational necessities. It invokes the language of ‘each help’, but it refrains from specifying what types such help should take, the diploma of effort required, or the factors by which compliance is to be assessed. In consequence, the Court docket’s reasoning seems to be centered on the prohibition of obstruction, thereby leaving the constructive element of the responsibility largely undeveloped. The UNRWA advisory opinion additionally raises an additional concern regarding the scope of co-operation. In deriving the responsibility from Article 2(5) of the UN Constitution, the Court docket implicitly interprets the phrase “any motion” to embody UNGA resolutions [p. 55, paras. 175, 177]. Notably, nonetheless, the Court docket doesn’t have interaction with the non-binding character of such resolutions. This omission prompted disagreement amongst ICJ judges. Vice-President Sebutinde [p. 29, para. 91] and Judges Abraham and Cleveland [p. 2, para. 6] rejected this broader interpretation, arguing that the responsibility to co-operate is proscribed to binding “actions” of the UN, equivalent to Safety Council resolutions adopted underneath Chapter VII. Of their view, extending Article 2(5) to non-binding GA resolutions would successfully remodel such resolutions into binding obligations. This restrictive studying, nonetheless, conflates the implementation of resolutions with the distinct responsibility to co-operate, thereby depriving Article 2(5) of impartial normative content material. Because the Court docket itself emphasises, the responsibility to co-operate is designed to make sure the efficient fulfilment of the UN’s mandate by requiring States to chorus from obstructing its operations. This broader interpretation was endorsed by Choose Xue [p. 3, para. 11] and is implicitly supported by the Court docket’s reasoning [ibid.]. But, by failing to deal with the disagreement explicitly or to make clear the bounds of Article 2(5), the Court docket leaves unresolved a central query relating to the scope of Constitution-based co-operation, reinforcing the broader sample of normative ambiguity that characterises its current jurisprudence on the responsibility to co-operate.
Against this, within the local weather change context, the Court docket articulates the responsibility to co-operate with significantly better precision. There, co-operation serves a preventive and managerial operate, geared toward defending a worldwide widespread good by means of sustained collective motion. This useful orientation permits the Court docket to border co-operation as an obligation of conduct, topic to a due diligence customary, and to establish concrete types of co-operation—monetary help, know-how switch, and capacity-building—whereas accommodating differentiated capacities. The relative readability of this mannequin solely accentuates the indeterminacy of the co-operation duties articulated within the jus cogens and UN Constitution contexts.
Co-operation with out Coherence?
Taken collectively, the Court docket’s jurisprudence means that useful differentiation in line with the aim of the co-operation might assist clarify why the content material varies throughout authorized regimes. Specifically, the Court docket seems to differentiate between co-operation as collective enforcement; co-operation as institutional facilitation, inherent in membership of the UN; and co-operation as preventive and managerial governance, geared toward defending international widespread items. Whereas differing features might justify variations within the modalities of co-operation, they don’t clarify why the Court docket grounds this responsibility in several authorized bases with out clarifying how these bases relate inside a coherent framework. But, from the attitude of systemic integration—mirrored in Article 31(3)(c) of the Vienna Conference on Treaty Legislation—there’s at the very least a presumption that the place the identical obligation is invoked throughout completely different contexts, obligations grounded in several authorized bases must be able to working coherently inside a single, unified authorized order, slightly than giving rise to markedly divergent scopes and contents, a presumption the Court docket leaves largely unexplored. Within the two contexts the place the stakes are arguably excessive—severe breaches of peremptory norms and the constitutional functioning of the UN—the duty is framed in emphatic, even absolute, phrases, but stays strikingly under-specified in its scope, modalities, and authorized penalties. In consequence, the responsibility to co-operate emerges not as a unified authorized obligation able to systematic software, however as a context-dependent assemble whose authorized foundation, depth, and operational necessities fluctuate throughout regimes.
This divergence might be rationalized by reference to the excellence between co-operation as a secondary obligation, triggered by an internationally wrongful act, and co-operation as a major obligation, flowing instantly from treaty legislation, customized, or institutional membership. On this view, the responsibility articulated within the 2024 Authorized Penalties advisory opinion can be secondary in nature, whereas the duties recognized within the Local weather Change and UNRWA opinions would function as major obligations. But, this distinction finally considerations the mode of triggering the duty, not its substantive content material. It doesn’t clarify why co-operation articulated as a response to an internationally wrongful act—arguably the context wherein the necessity for authorized steering is most acute—is framed in emphatic but under-specified phrases.
An additional clarification might lie within the political sensitivity of the contexts wherein the Court docket is working. Within the Palestine-related advisory opinions, together with UNRWA and Authorized Penalties, the articulation of concrete constructive duties of co-operation would danger being perceived as prescribing particular programs of motion in an ongoing and extremely contested scenario. The Court docket’s reluctance to specify the content material and limits of the responsibility in these circumstances might due to this fact replicate a type of judicial self-restraint, geared toward preserving institutional legitimacy and avoiding accusations of political overreach. Against this, the local weather change context, whereas politically salient, considerations a structurally completely different downside, particularly a diffuse, long-term international danger ruled by established treaty frameworks and technocratic modes of co-operation. In that setting, the Court docket seems extra prepared to articulate co-operation with doctrinal precision, framing it as an obligation of conduct topic to due diligence and figuring out concrete modalities of compliance.
If political sensitivity does affect the Court docket’s willingness to specify the content material of the responsibility to co-operate, nonetheless, this solely reinforces the normative concern. Permitting the readability of authorized obligations to fluctuate in line with political context dangers reworking co-operation right into a variable customary whose authorized content material relies upon much less on precept than on institutional prudence.
Conclusion
Throughout its advisory opinions, the Court docket invokes co-operation as a norm of appreciable significance, but leaves its supply, scope, and content material insufficiently specified, rendering the duty inclined to competing and doubtlessly inconsistent interpretations. This lack of readability is especially hanging given the normative weight the Court docket itself attributes to co-operation, not merely as a programmatic aspiration however as a constitutive aspect of what’s typically described within the literature because the transition from a conventional ‘legislation of co-existence’ to a extra built-in ‘legislation of co-operation’ [n 1].
If co-operation is to operate as a real authorized obligation, it requires a extra coherent and internally constant doctrinal framework. Absent such clarification, co-operation dangers remaining an open-ended idea whose authorized power varies unpredictably throughout contexts, undermining each its normative authority and its sensible utility. The fragmentation noticed within the Court docket’s current advisory opinions thus doesn’t merely replicate doctrinal nuance, however raises broader considerations in regards to the operability of co-operation as a binding authorized customary.
A extra holistic and systematizing engagement with the responsibility of co-operation would have been preferable, because the ICJ as a substitute permitted fragmented formulations to emerge throughout authorized contexts devoid of doctrinal coherence. The implications of this uncertainty for State compliance shouldn’t be underestimated. The place the content material and scope of an obligation stay indeterminate, States are afforded important latitude to interpret their duties narrowly, significantly in politically delicate contexts. This danger is amplified in a interval marked by resurgent unilateralism, protectionism, and strategic disengagement from multilateral frameworks. In such a local weather, an obligation to co-operate articulated in indeterminate phrases might wrestle to information and constrain State conduct.
