Questioning the Peremptory Status of the Prohibition of the Use of Force

Dr James A. Green is lecturer in law at the University of Reading School of Law.

The prohibition of the unilateral use of force, as set out most crucially in Article 2(4) of the UN Charter, is often seen as the archetypal example of a jus cogens norm. Certainly, an overwhelming majority of scholars view the prohibition as having a peremptory character, as does the International Law Commission and the International Court of Justice.  It is understandable that a plethora of commentators have perceived the prohibition as a peremptory norm: the use of military force usually involves the systematic killing of human beings, often on a vast scale.  An underlying rationale for the entire jus cogens concept is the desire to impose some kind of fundamental standard of common values upon state interaction and to strengthen the effectiveness of international law in certain areas of common concern.  On this basis, the prohibition of the use of force is exactly the sort of norm that should be peremptory. Coupled with the fact that jus cogens and the jus ad bellum share common natural law underpinnings, one might view them as a perfect conceptual fit.

In ‘Questioning the Peremptory Status of the Prohibition of the Use of Force’ (2011) 32 Michigan Journal of International Law 215-257, I challenge this widely held view: is the prohibition of the use of force in fact a jus cogens norm?  The desirability of peremptory norms, and, indeed, their very existence, has been questioned in the literature, but it was not my aim in the Article to debate the existence of jus cogens norms per se.  Without making a value judgment as to the desirability of peremptory norms, the view is taken that there is certainly enough evidence to suggest that states have accepted the general notion of jus cogens flowing from Article 53 of the Vienna Convention on the Law of Treaties.

Based on this starting point, the Article does not argue that the prohibition is necessarily a norm that has failed to achieve peremptory status.  Rather, the intention is to demonstrate that there are significant difficulties with such a conclusion and that, as a result, the widespread uncritical acceptance of the prohibition as a jus cogens norm is concerning.  The aim is to test the prohibition against the criteria for the establishment of peremptory status—“a norm accepted and recognized by the international community of States as a whole as a norm from which no derogation is permitted and which can be modified only by a subsequent norm of general international law having the same character.”

By way of background, then, the Article sets out in more detail the legal criteria for identifying a peremptory norm of international law, and goes on to consider the majority view—prevalent in the literature—that the prohibition of the use of force is such a norm.  A number of problems with the conclusion that the prohibition is jus cogens are then set out.  The question of whether the prohibition is suitable, or even capable, of being viewed as a jus cogens norm is examined through various points of focus.

First, it is argued that the conjoined nature of the prohibition of the use of force with the prohibition of the threat of force in Article 2(4) leads to difficulties, given that the ban on the threat of force is clearly not peremptory in character.  Article 2(4) as whole, therefore, cannot be peremptory.  This is problematic, as the two prohibitions are generally viewed as being intertwined.  However, this would not necessarily stop the prohibition on the use of force (if divorced from the threat of force) from taking on peremptory status.

A more fundamental issue is then examined: the exceptions to the general prohibition of the use of force. Given that these exceptions – self-defence and collective security – are universally accepted, it is impossible to conclude that the prohibition is, in itself, peremptory (as peremptory norms allow for no derogation).  If one is to hold that the prohibition is jus cogens, a suitable norm must be constructed to take into account the right of self-defence and Security Council authorized collective security actions.  Yet any attempt to formulate such a norm is problematic given that certain aspects of the jus ad bellum are clearly not peremptory (e.g., the ‘reporting requirement’), while other rules must be for the norm to function (e.g., ‘proportionality’).  As such, the selection of rules for the avowed peremptory norm is a difficult process, and the number of interrelated rules involved makes any norm constructed overly long and unclear.  Adding to this lack of clarity is the fact that many of the rules that must necessarily form part of the peremptory norm are themselves uncertain in terms of content or scope, such as the inherent flexibility of the ‘necessity’ criterion for self-defence.

The Article then highlights that the restrictive nature of the jus cogens framework does not seem to fit with the reality of the development of the law on the use of force.  If jus cogens norms can only be altered by other jus cogens norms, and the prohibition has attain this status, then the future development of the jus ad bellum would be notably inhibited.  This does not seem to accord with the reality of the law on the use of force, which is continually developing.  Examples of current arguable shifts in customary international law—self-defence against non-state actors and cyber-attacks—are used to demonstrate this problem of a “frozen” jus ad bellum.

Finally, examples from state practice are examined to ascertain the extent to which states have in fact accepted the peremptory status of the prohibition.  It is argued that while some states have certainly affirmed the view that the rule is a jus cogens norm, it is unclear whether this acceptance has been enough to confer peremptory status on the prohibition.  The Article takes the positivist position that jus cogens norms can only be created through the consent of states, as evidenced by their practice.  That a claim as to peremptory status is advanced by writers, however frequently, is not enough to turn an “ordinary” norm of international law norm into a “supernorm” of jus cogens.  It is unclear whether the “international community of States as a whole” has truly “accepted and recognized” the peremptory status of the prohibition on the use of force as is so often claimed.  It is acknowledged, however, that the brief study of the state practice conducted in the Article does not establish a conclusive position on the issue either way.

At face value, the various concerns expressed could well be regarded as boiling down to a single issue of semantics.  The prohibition of the use of force is undeniably accepted by all states prima facie, and applies universally.  Therefore, what difference does it make whether the norm is labelled “jus cogens” or not?  It is unlawful to use force if the peremptory character of the rule is accepted, but then, it is also patently unlawful if it is not.  The importance of the peremptory status (or lack thereof) of any given rule can therefore be overstated.

Nonetheless, a jus cogens norm potentially has an additional “compliance pull” to it.  The widespread acceptance of the jus cogens concept means that states are more likely to take special note of peremptory norms and will potentially comply with them more often than with other rules. More practically, a jus cogens rule does not merely find contrary practice unlawful, it voids the formation of new contrary norms ab initio.  Whether these implications of peremptory status are seen as “good” depends on one’s views as to the desirability and functionality of the jus cogens project in international law.

If one takes the view that jus cogens plays, or can play, a positive role in securing world order—strengthening and protecting fundamental values, as well as restraining unchecked power—then it is surely desirable that any purported jus cogens norms are clear, identifiable, and properly constituted.  If one subscribes to the desirability of value-based “supernorms” in the international system, then the prohibition of the use of force would surely be a norm that one would want to ascribe such a character to.  The problems highlighted in this Article have implications for the legitimacy of that rule, and thus its compliance pull, at least in a relative sense when it is found to be in opposition to other, potentially less “fundamental,” norms.

Conversely, if one takes the view that jus cogens norms represent a creeping imposition of a particular value-set and an unwarranted and dangerous erosion of state sovereignty, it is equally desirable that the peremptory status of the prohibition be properly tested and critiqued. For those that argue against the “relative normativity” of rules within the international legal system, the analysis of the peremptory status of the prohibition of the use of force in this Article may usefully highlight more pervading problems inherent in the jus cogens concept.

Thus, the Article leaves it to the reader to take his or her own view as to the utility of its critique. Ultimately, this is because neither “desirability” nor “undesirability” have any legally constituting effect with regard to the creation of jus cogens norms.  For all of jus cogens’ natural law gloss, the concept remains grounded in positivist international law.  Indeed, it must remain so if it is to have any credibility or weight in a system that, for better or worse, remains primarily premised upon state consent.  For a norm to be seen as a rule of jus cogens, it must meet certain positivist criteria.  Without entirely excluding the possibility that the prohibition of the use of force is a peremptory norm, the Article aims to highlight that the rule’s jus cogens status—when tested against these criteria—is extremely problematic.  At the very least, it must be said that the widespread uncritical acceptance of the prohibition’s peremptory nature is concerning, particularly as the norm is one that forms a cornerstone of the modern international legal system.