Security Council Resolutions as Evidence of Customary International Law

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In 2012 the International Law Commission began to address one of the last major uncodified areas of public international law: how norms of customary law (CIL) are to be identified.  The exercise at the ILC has not been an easy one.  States commenting in 2016 on the Commission’s “draft conclusions” expressed concerns on a variety of issues.  One of the most contentious was the role of international organizations (IOs) in the creation of custom. 

The topic has been the subject of academic conferences at the University of Manchester, the University of Michigan and elsewhere, as well as a growing volume of law review commentary (see here, here, here, here and here).  And in early January, the United States submitted comments on the draft conclusions that were, to put it mildly, opposed to any role for IOs.  Closer to home, Kristen Boon, Isaac Jenkins and I have just published an article on the role of the Security Council in generating evidence of custom related to non-international armed conflicts (NIACs), an area of intense Council involvement. In this post I’ll describe the ILC’s view of IOs, the United States’ response, and then our affirmative arguments specific to the Security Council.

The ILC addresses IOs’ role in generating custom in two of its draft conclusions.  First, Conclusion 4(2) on the “Requirement of Practice” provides, “In certain cases, the practice of international organizations also contributes to the formation, or expression, of rules of customary international law” (p 76).  Second, Conclusion 12 addresses “Resolutions of International Organizations and International Conferences”:

  1. A resolution adopted by an international organization or at an intergovernmental conference cannot, of itself, create a rule of customary international law.
  2. A resolution adopted by an international organization or at an intergovernmental conference may provide evidence for establishing the existence and content of a rule of customary international law, or contribute to its development.
  3. A provision in a resolution adopted by an international organization or at an intergovernmental conference may reflect a rule of customary international law if it is established that the provision corresponds to a general practice that is accepted as law (opinio juris) (p. 78).

On their face, these provisions represent a modest relaxation of the traditionally state-centric nature of CIL.  But ambiguities abound.  Article 4’s statement that “in certain cases” IO practice may contribute to CIL provides no detail on the circumstances in which that might happen.  Article 12 is a bit more specific, focusing on IO resolutions, but in saying only that such resolutions “may provide evidence for establishing the existence and content of” CIL, it provides no guidance on when or how that might occur.   Nor does either provision address how IO practice of any sort might embody either or both of the two traditional elements of CIL, practice and opinio juris.

Adding to this ambiguity is the ILC’s extraordinarily limited notion of when an IO acts in its own legal capacity for purposes of contributing to CIL, as opposed to merely serving as a forum in which its member states express their own views.  The Commission states in commentary that this should occur most clearly “where member States have transferred exclusive competences to the international organization.”  (p. 89).  The sole example given is the European Union and it is difficult to think of others.   IOs may also act on their own behalf when member states “have conferred powers upon the international organization that are functionally equivalent to the powers exercised by States.” (id.). An example of those actions is IO secretariats serving as treaty depositories.  (id).  Acts not functionally equivalent to those of states “are unlikely to be relevant practice.” (id.). This last category would seem to encompass most IO actions. 

The ILC underlines this exceptionally narrow view of IO corporate action in a comment on the “certain circumstances” language in Conclusion 2: “References in the draft conclusions and commentaries to the practice of States should thus be read as including, in those cases where it is relevant, the practice of international organizations.”  (p. 88). Most IO practice, in other words, is actually state practice. 

The ILC’s narrow approach continues when it discusses the United Nations, the IO most frequently cited as a source of custom.  While one might imagine UN organs with specific competences having a role in generating evidence of custom in those areas, the ILC commentary discusses only resolutions of the General Assembly (p 107).   Readers are left to wonder whether this is because, in the Commission’s view, only the GA can contribute to custom by virtue of it being “a plenary organ of near universal participation,” (id.) or whether it is just the best example among many others.  The most obvious explanation is that the ICJ has cited almost exclusively to GA resolutions when invoking IO practice in cases such as Congo/Uganda (¶168), Nicaragua (¶195) and the Nuclear Weapons Advisory Opinion (¶70).

But even this narrow view of IOs’ role in CIL was unacceptable to the United States.  In comments submitted to the Commission on January 5, the US ruled out any role for IOs: “It is axiomatic that customary international law results from the general and consistent practice of States followed by them out of a sense of legal obligation.” (p. 2; emphasis in original). The US argued “there is no support” for the “some circumstances” language in Conclusion 4(2) and proposed that the section be deleted entirely. (p. 5).  Following on this position, the US described IO resolutions (the subject of draft conclusion 12) as embodying “the opinio juris of States, although potentially also their practice.” (p. 17).

Perhaps anticipating that this categorical position would not carry the day in the Commission, the US went on argue that even if one accepted a role for IOs in CIL, Conclusion 4(2) and accompanying commentary is vague and question-begging in ways that mirror many of the problems noted above (pp. 3-5).  These objections are thought-provoking are deserve serious consideration, even if one supports an IO role in custom.

The proposal that Kristen, Isaac and I make, however, rests on several facts and legal propositions neither side in this debate has raised.  We argue that the Security Council regularly and consistently imposes obligations on parties to NIACs that differ in important ways from otherwise applicable international law or, in some cases, from one side in a dispute over the content of a particular customary norm.  We created a dataset of all Security Council resolutions on the most significant NIACs from 1990-2013 and coded them for the imposition of binding obligations on a range of international law issues. 

Two findings from the data stand out.  First, the Council has been omnipresent in contemporary NIACs, passing at least one resolution on 76% of all NIACs from 1990 to 2013, increasing to 80% for NIACs that began after 1990.  Second, the Council imposed obligations that are highly relevant to several unresolved CIL debates.  In particular, our data show that the Council required non-state actors (usually armed rebel groups) to respect human rights in 68% of NIACs in which it had invoked Chapter VII and in 83% of such conflicts that commenced after 1990.  Similarly, the Council ordered non-state parties to abide by NIAC peace agreements in 83% of conflicts with such agreements, and in 92% of such conflicts in which it invoked Chapter VII.   We argue these findings are evidence of CIL with regard to whether non-state parties are bound by human rights obligations and whether peace agreements ending NIACs are legally binding.  Both issues are highly contested and the addition of Council practice could well sway the debates.

From a theoretical perspective, we argue that when the Council imposes such obligations it acts as an agent for all UN member states.  Article 24(1) of the Charter provides that member states “confer on the Security Council primary responsibility for the maintenance of international peace and security, and agree that in carrying out its duties under this responsibility the Security Council acts on their behalf.   (emphasis added).   The Special Court for Sierra Leone relied on an Article 24(1) agency theory to hold that an agreement between Sierra Leone and the UN was, as a result of Council approval, “an agreement between all members of the United Nations and Sierra Leone.” (Prosecutor v. Taylor, Case No. SCSL-2003-01-I, Decision on Immunity from Jurisdiction, ¶38 (May 31, 2004) (emphasis in original). 

Does the agency theory mean that member states have delegated to the Council a capacity to contribute to CIL?  In its ILC submission, the US argued emphatically not: the mandates of IOs are “carefully negotiated treaties” that “rarely, if ever” provide an express authorization “that the organization exercise the powers of member States to generate practice for purposes of customary international law.” (p. 4).  This was obviously true when the UN Charter was negotiated.  But the US position seems anachronistic today.  Consider the consequences of states having delegated to the Council authority to address an extraordinary range of legal questions arising from NIACs – and having done so for more than 25 years — but withholding any CIL consequences of that delegation.   Those consequence – i.e. evidence of custom — would not be attributable the Council.  But neither would they be attributable to the member states, who would have delegated the authority to act to the Council, effectively disengaging those acts from their (state-based) customary law implications.  Member states cannot claim ownership of acts they have delegated to the Council.  The acts would thus disappear into a legal black hole.  An entire realm of rich international practice in responding to and remediating NIACs would be lost to CIL.

Second, the post-Cold War Council has developed a set of legal tools to address NIACs that no state possesses individually.  It can impose obligations on non-state rebel groups.  Under Charter Article 2(7) it can address NIAC issues normally within a state’s domestic jurisdiction. And it can legitimize or delegitimize the use of force by some or all NIAC parties.  Council acts pursuant to these exclusive powers cannot be attributed to member states.

Third, our data show a Council involved in almost all contemporary NIACs.  The Council has addressed NIACs in every year, in every region, of varying duration, of varying number of actors, of varying battle deaths and civilian casualties, at various points in the conflicts, and both inside and outside the spheres of influence of every hegemonic state.  No state or group of states comes close to matching this breadth of practice.  The nature of Council involvement is also remarkably deep, ranging from simply imposing obligations to dispatching peacekeeping missions to imposing sanctions.  To take sanctions as an example, only four of the sixteen Council sanctions regimes in place in 2017 targeted state actors exclusively; the rest targeted non-state actors exclusively or both state and non-state actors.   Obviously, no state or group of states has addressed NIACS more broadly or more comprehensively.

In sum, the Council has exercised unique Charter to powers to intervene in extraordinarily intrusive ways into the most severe NIACs of the post-Cold War era.  It has done so using authority specifically delegated by all member states.  And in its interventions, the Council has consistently imposed the same obligations on NIAC parties for over two decades, despite wide variations in the causes, location, severity and duration of the conflicts.         

This is not to say the case for considering Council practice as evidence of custom is an easy one.   Many other objections can be raised, most of which we address in our article.  Circling back to the US objections outlined above, we believe our views are potentially consistent with its position that while an IO can never contribute to custom on its own behalf, IO resolutions can be evidence of state practice.   If UN member states have enlisted the Council as their agent to address legal issues in NIACs, then Council practice is ultimately state practice, since member states are the principals in the principal-agent relationship.   The US omits discussion of the agency provision of Charter Article 24(1), perhaps because it, like the ILC, is focused almost exclusively on the General Assembly.   But our view would admit Council practice to the mix of evidence relevant to custom while not radically departing from the fundamentally statist conception of CIL the US advances.

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Dapo Akande says

March 1, 2018

Dear Greg,

Thanks for the post! I am really looking forward to reading this article on a very interesting issue.

I was wondering if the US' statement that described IO resolutions as embodying “potentially" embodying the practice of states (in addition to their opinio juris) is a change of position from that taken around the time of the Nicaragua case. If I remember correctly, the US and some US scholars, criticised the Court for using UN General Assembly resolutions as indications of state practice. They took the view, I think, that at best those resolutions could only represent opinio juris. Certainly the US has taken the view in other contexts (and I am thinking most notably of international humanitarian law) that words by states do not constitute state practice.

You seem to suggest that imposition of obligations by Security Council might be relevant to the formation of customary international law. It might that the language you use in the article is more nuanced but wouldn't there be an opinio juris problem here? If the Council is imposing an obligation then is that not a recognition that this is an obligation that does not otherwise exist, thus negating any value that resolution might have as opinio juris for the purposes of customary international law? It would be different if the Council were recognising existing obligations/ affirming them/ seeking compliance with them etc etc

Finally, it seems to me that if the relationship between the UN (when acting through the SC) and its members were one of agency, because of Art. 24, the consequences would be very far reaching. It would mean that the all UN members bear legal responsibility for acts of the SC when acting under Art. 24. That there is not such general responsibility for UN members of acts of the UN might suggest that the relationship is not seen as one of agency despite the words you rightly point to in Art. 24. The decision of the Special Court for Sierra Leone in the Taylor seems to me to very much a stretch by which I mean wrong!

Greg Fox says

March 2, 2018

Dear Dapo –

Thanks very much for these very interesting questions!

On a changing US position regarding GA resolutions. I cannot recall now an official US reaction to the Nicaragua opinion arguing that GA resolutions are not evidence of state practice. But you are certainly correct that many US scholars criticized the opinion on that basis, most notably Tom Franck and Anthony D’Amato in 1987 AJIL pieces. Assuming the US did take this position, is their new comment a clear change? Note that the US is quite tentative on this question: IO resolutions “may provide relevant information” regarding the opinio juris of states, “although potentially also their practice.” In a part of the comment I did not quote in my post, the US explains further that because states may support IO resolutions for a variety of political reasons, and because many states simply don’t have the capacity to vet the large volume of resolutions, “even widely supported resolutions may provide limited or ambiguous insight into the practice and opinio juris of the States that support them.”

It is possible the US has in mind a set of IO resolutions that did not exist at the time of Nicaragua. These are the Security Council’s so-called legislative resolutions, such as 1373, 1540 and 2178. Because these resolutions require all member states to take concrete steps they could be viewed as evidence of practice. In this, the legislative resolutions (and all the Council resolutions we coded as binding) resemble national legislation, an uncontroversial source of practice.

It is admittedly difficult to distinguish current General Assembly resolutions from those the US apparently discounted in the 1980s. So perhaps, in opening the door just a crack for resolutions to serve as evidence of practice, the US was simply reserving the ability to distinguish GA resolutions it dislikes (i.e. on expropriation) from those it supports (the whole raft of counter-terrorism resolutions).

On your question of how SC resolutions can provide opinio juris. We do not take the position that any of the patterns of obligation we identify can, by themselves, create CIL rules. The patterns are one type of evidence to be considered alongside other evidence, virtually all of it traditional state practice. So all of the norms we discuss as potentially affected by Council practice already enjoy a foundation in sources outside the Council. In fact, many resolutions we coded simply reaffirm uncontroversial existing customary and treaty-based obligations. The more interesting patterns in the data concern unresolved and hotly-contested issues of CIL. Two we cite in the post are the human rights obligations of non-state actors and the question of whether NIAC peace agreements are legally binding. In those cases, the Council has weighed in on one side of an ongoing debate. Again, a foundation in state practice already exists.

One important feature of the coded resolutions is that they are all conflict-specific. They are not self-consciously designed to affect CIL in the manner of GA resolutions like the Friendly Relations Declaration or the Definition of Aggression. So when the Council imposes obligations by legislative fiat in our resolutions, they are doing so for the specific conflict being addressed. In the article we address the objection (which may be yours as well) that conflict-specific resolutions lack opinio juris value, since all the Council is doing is trying to solve immediate and specific problems.

In our view, this raises the bar for acceptable evidence of opinio juris to impossible heights. The ICJ has consistently suggested that opinio juris can be implied from practice, though the ILC in its draft conclusions rejects this view. In our view, the Council’s consistent set of preferences expressed over many years in diverse conflicts can give rise to opinio juris.

We would also point again to national legislation: it is regularly endowed with opinio juris value despite generally lacking any specific references to CIL. Since many of the most interesting NIAC norms concern governance issues similar to those addressed by national legislation (i.e. restructuring the legal, political and economic institutions of post-conflict states), we think this comparison is particularly telling.

Finally, we argue that a high bar for opinio juris simply ignores reality. Much social science scholarship has shown the important role IOs have in fact played in shaping the perception and direction of international norms.

On your very interesting question of whether viewing the Council as an agent for member states would lead to their bearing responsibility for wrongful Council actions. This is an issue we do not explore in the article. It is also one that rarely, if ever comes up in practice, since when the UN as a corporate entity is sued in national courts, the UN then invariably asserts immunity. Moreover, Kristen and I think this question raises issues of a fundamentally different character from the Council’s functioning as an agent for purposes of contributing to CIL. Your question is one of responsibility (secondary norms), not formation of law (primary norms). As you know, the debate over IO responsibility, and the ILC’s draft articles in particular, is ongoing and unresolved. For example, the Shares Project in Amsterdam ( in which Kristen is involved, has explored concurrent liability between states and IOs. More fundamentally, some argue that the whole idea of a secondary law of IO responsibility is premature, given the weakness of clear primary rules applicable to IOs.

So this is all to say that while one could argue that Council agency for CIL purposes inexorably leads to its agency for responsibility purposes, these are different points on the timeline and there are many disputed and unresolved steps between the two propositions.

Dapo Akande says

March 3, 2018

Hi Greg,

Thanks very much for your answers. All very helpful. I share your view that the fact that a resolution is conflict-specific does not mean that it cannot contribute to opinio juris or to the formation of custom. My question was more about whether "imposition" of obligations counts. When the Council "imposes" an obligation is it not in a sense similar to "imposition" of obligations by treaties, which we would not count towards opinio juris for the formation of custom unless the treaty (or its negotiating history or subsequent practice) recognises that this obligation is also one in customary law.

Your point about the question of responsibility rarely coming up in practice goes precisely to my point about the SC being regarded as the agent of member states. One could argue that it does not come because the SC is not regarded as an agent. If it were to come up, it would come up by member states being sued for acts of the UN (rather the UN itself being sued). I take your point though that you regard agency for CIL purposes as being different from agency for responsibility purposes. I suppose that is where we perhaps take different views in that I am assuming that if there were a relationship of agency it would follow that the UN was responsible.

Thanks again for the piece! Much food for thought. I should say that despite my questions above I do agree with the conclusion that we should be looking at practice in the SC for evidence of practice and opinio juris contributing to the formation of custom. It is just that I would be using this as evidence of state practice much in the vein of Rosalyn Higgins' work on The Development of International Law Through the Political Organs of the UN

Lorenzo Gasbarri says

March 4, 2018

Dear both,
Thank you very much for the interesting post and discussion.

I believe there is a fundamental question on the background: is it possible to distinguish between the practice of the Security Council as such and the practice of the States members of the Security Council when they act in the framework of this organ? I believe it is only a matter of perspective. If you focus on member states, you end up endorsing a version of agent theory, culminating in delegation (attributed/implied powers). If you focus on the organization, you end up valorizing autonomy and the practice of the organ as such, culminating in inherent powers established in customary law (Seyersted’s notion). Even the ICJ moves from one perspective to the other (cf. “Nicaragua” and “Certain Expenses”, for instance). However, we are discussing the same object, what the ILC calls “rules of international organizations”.

On this topic I presented in Manchester, and you can find my contribution here: Similarly to your project, I focus on the imposition of obligations on third parties, which is not a peculiarity of Security Council’s resolutions, involving other acts and other organizations. In order to find a synthesis of the two perspectives, I focus on the notion of "rules of international organizations" and their interaction with treaty law and customary law.

Greg Fox says

March 6, 2018

Dapo -

Just one final comment on your "imposition" point. In my view, SC practice does not fit neatly into a distinction between imposed obligations and those self-consciously accepted by states as relevant to CIL. In part this is because of the agency theory: the Council is not neatly separable from the states subject to its obligations. In part it is because, as we detail in the article, the Council has taken a host of actions on NIACs that are legally unavailable to states acting individually. In part it is because some of the Council's most innovative obligations are imposed on non-state actors, whose consent is not relevant to CIL. And in part it is because of the need to take account of the Council's omnipresence in contemporary NIACs. On key issues we identify, Council-imposed obligations now make up a substantial portion of international practice. UN member states have chosen to work through the Council as opposed to taking individual actions with individual expressions of opinio juris . Should this choice -- made for laudable reasons of efficiency and collective action -- be made at the cost of the resulting practice dropping out of the CIL mix? Perhaps. But in our view this far from an obvious conclusion.