Conceptual and Practical Problems in the Change or Termination of Rules of Customary International Law
by Alvin Yap
Published on 18 November 2022
Once in existence, how do rules of customary international law change or terminate? This topic was intentionally not dealt with by the International Law Commission (ILC) in its Draft conclusions on identification of customary international law (see Commentary (5) to Draft Conclusion 1). Yet, it is a matter of significant academic and practical interest. This post raises a few general points concerning how rules of customary international law could change or terminate.
Relationship between identification and development
First, what is the relationship between the process of identifying a rule of customary international law and the process of determining whether that rule has changed or died? In its draft conclusions on identification of customary international law, the ILC observed that there is a relationship between the two processes, but did not specify the exact nature of that relationship. In the words of the ILC:
‘Dealing as they do with the identification of rules of customary international law, the draft conclusions do not address, directly, the processes by which customary international law develops over time. Yet in practice identification cannot always be considered in isolation from formation; the identification of the existence and content of a rule of customary international law may well involve consideration of the processes by which it has developed. The draft conclusions thus inevitably refer in places to the formation of rules of customary international law. They do not, however, deal systematically with how such rules emerge, change or terminate.’ (see Commentary (5) to Draft Conclusion 1).
The ILC emphasized that in the identification of customary international law, one must apply the ‘two-element approach’ (see Commentary (1) to Draft Conclusion 2), which involves inquiry into two distinct questions: is there a general practice; and whether such general practice is accepted as law. Both elements must be present for a rule to exist under customary international law. How does the two-element approach apply to the determination of whether a rule of customary international law has changed or terminated?
The question appears to pose less difficulty in determining whether a rule of customary international law has developed into a new one. In that case, the process of identifying the new rule is not fundamentally different from identifying whether a rule exists in the first place: if there is sufficient evidence of a general practice and opinio juris supporting the existence of the new rule, one may conclude that the old rule has developed into the new rule. If one of the two elements of the new rule is not present, the old rule remains.
That analysis should not be equally applied to a situation when one is determining if a rule of customary international law has terminated. Termination and change are not the same concepts. A rule may terminate without another rule taking its place. For example, if a rule of customary international law obliges States to take a particular action, that rule may terminate without another rule taking its place. In that case, States are simply no longer obliged to take that action. It is not necessarily the case that a new obligation must take the place of the old, extinguished obligation.
Thus, the question remains: how does one determine whether a rule of customary international law has terminated? In particular, based on the two-element approach, is a rule of customary international law extinguished by the loss of one of the two elements? Or does it require the loss of both elements? For example, if there is a rule of customary international law that obliges State to refrain from taking a particular action and, over time, a general practice develops of States taking that action, is that sufficient to conclude that the rule is no longer in existence? Or it is necessary to also investigate why States are taking that action despite the existence of the rule? If so, does it matter if the conduct contrary to the pre-existing rule was carried out in intentional breach of the said rule, or in good faith attempt to develop or terminate it? These questions cannot be easily answered and I do not propose to do so here. Rather, the point is that the two-element approach used in the identification of a rule of customary international law should not be blindly applied to the determination of whether a rule has terminated.
Another interesting aspect of the relationship between the identification of a rule of customary international law and its change or termination lies in the phenomenon that, in practice, once a rule has been identified to exist under customary international law, there appears to be a presumption that the rule continues to exist, at least for some time. For instance, once a rule has been ascertained to be a rule of customary international law by the International Court of Justice (ICJ) or the ILC, for some time, that determination carries such significant weight that it precludes a challenge of whether the rule still exists. In that way, the identification of a rule of customary international law, particularly by certain authoritative bodies, would seem to inhibit the process by which the rule develops or terminates.
Change and termination of a rule of customary international law reflected in a treaty
Second, when a rule of customary international law is reflected in a widely ratified multilateral treaty, how can that rule be changed or terminated? For States parties to that treaty, any conduct that seeks to terminate the rule is more likely to be characterized as a breach of the rule and the treaty. It is difficult to see how States parties to a treaty can lawfully terminate a rule of customary international law reflected in that treaty for as long as they remain parties to the treaty.
There appears to be greater possibility, at least in theory, for States parties to change (rather than terminate) a rule of customary international law contained in a treaty given that they may behave in a way that deviates from, but not breach, the rule. However, one potential obstacle is the issue of applicable law. A treaty may apply to the exclusion of customary international law on the same subject matter, preventing States parties to that treaty from invoking, let alone change, the customary international law. This is illustrated in the Jadhav case, in which India alleged that Pakistan breached Article 36 of the 1963 Vienna Convention on Consular Relations (VCCR) by denying consular access to Mr. Kulbhushan Jadhav, an Indian national. Pakistan sought to rely on an exception under customary international law to the right of consular access in prima facie cases of espionage. The ICJ held that Article 36 of the VCCR expressly governs the right of consular access and excludes the application of customary international law as between State parties to that treaty, including India and Pakistan (see paragraph 89 of the Judgment). Thus, even if there were such an exception under customary international law, Pakistan could not rely on it.
Compared to State parties, non-State parties to the treaty may be thought to be in a better position to influence the development of the rule of customary international law. Not bound by the treaty, they are bound exclusively by the rule as it exists under customary international law. Their conduct cannot be characterized as performance (or breach) of the treaty and operate exclusively within the realm of customary international law. In practice, however, precisely because of how influential non-State parties can be in changing a rule of customary international law, their conduct is often under close scrutiny from other States. Conduct aimed at changing a rule of customary international law may be met with protests from other States, which prevent the rule from developing. This is illustrated by the Alleged Violations case. In that case, Colombia argued that, under customary international law, the powers of a coastal State in its contiguous zone have developed beyond those powers enumerated in Article 33 of the United Nations Convention on the Law of the Sea (UNCLOS) and now include the power to control security. The ICJ disagreed and found that although a few States enacted legislation that gave them the power to control security in their contiguous zones, those practice were met with opposition from other States (see paragraph 154 of the Judgment). Thus, the Court found that customary international law remained as reflected in Article 33 of UNCLOS.
Persistent objection to change or termination
Third, can there be a persistent objector to the change or death of a rule? The ILC recognized that where a State has objected to a rule of customary international law while it was forming, the rule is not opposable to it for so long as it maintains its objection (see Commentary 1 to Draft Conclusion 15). That deals with a situation where a State objects to the formation of a rule of customary international law. It does not directly address the situation where a rule of customary international law is unquestionably in existence, but it has changed or terminated. In that situation, if a State maintains its objection to the change or termination of the rule, is it entitled to rely on the old rule?
Where a rule of customary international law is changing into a new one, it is arguably analogous to a situation where a rule is forming where there was previously no rule. Thus, if the conditions for persistent objector status are met, there seems to be little difficulty, at least in principle, for recognizing that a State may be a persistent objector to the new rule of customary international law and be entitled to rely on the old one. The framework of analysis that applies to the formation of a rule of customary international law can be applied to the formation of a new rule of customary international law.
The same cannot be said about a situation where a rule of customary international law is terminated and no new rule takes its place. For example, is the concept of a persistent objector to the death of a rule inherently contradictory with the death of that rule? Put differently, if a State insists that a rule of customary international law remains in place and has not terminated, is that sufficient to keep the rule alive?
Assuming there can be a persistent objector to the termination of a rule of customary international law, a question concerns when the objection must be made. The objection might have to be made as soon as a State is aware that the rule is extinguishing. But that requires clarity on how and when a rule extinguishes. As discussed above, it is not clear whether a rule of customary international law is extinguished by the loss of one or both elements of general practice and opinio juris. Moreover, where a rule of customary international has been identified, States should be entitled to presume the existence of the rule and not lightly consider that the rule is being extinguished by conduct contrary to the rule.
As briefly canvassed above, there are conceptual and practical questions associated with changing and extinguishing a rule of customary international law. This is an area where there is limited real-world data and the discussion is necessarily more academic. Echoing the call in the introductory post for continued academic interest in customary international law, it is hoped that the questions raised in this post generate further consideration and debate in this area.
Alvin Yap is an associate at Squire Patton Boggs Singapore LLP, with a decade of experience representing States in State-to-State disputes. He is also a lecturer at the University of Western Australia.