Editor’s note: this webpage is the text of a portion of “Quantum of Silence: Inaction and Jus ad Bellum,” by Dustin A. Lewis, Naz K. Modirzadeh, and Gabriella Blum, HLS PILAC, 2019. A link to the PDF version of this part is available here, and a link to the full paper and annex is available here.

IV. Conclusion

Ultimately, there is no quantum of silence that has clear doctrinal force. While numerous States’ actions and statements implicate jus ad bellum, most of that conduct and most of those positions do not elicit a response (at least a publicly discernible one) by other international actors. Yet due to the structure of the field, attempts to discern — let alone develop — jus ad bellum invite presumptions about, and perceptions of, purported silence.

In light of the diversity of usages and the range of arguments for which silence has been deployed, it seems that silence does not carry a particular default brief. That is, an implied or express invocation of silence in this area is not itself determinative — or even necessarily suggestive — of a particular substantive outcome. That said, in practice, where scholars in this field invoke silence as legally significant, those invocations are more often than not offered in favor of relatively wide claims to resort to force.

As a matter of international law, it is unclear under what precise conditions silence may be accorded any legal significance. With regard to jus ad bellum, we have argued that caution is warranted in attributing legal effects to purported silence, whether of States or of the Security Council. This is particularly the case because not all States are apparently made aware contemporaneously of “article 51 communications” reported to the Security Council such that the purported silence of non-reactive States in respect of the legal claims that are made or the actions that are described in those reports may be considered deliberate or even conscious.

And yet, notwithstanding the jurisprudential difficulties, as a matter of practice silence by both States and the Security Council is being invoked — apparently increasingly — by several scholars in support of legal arguments in this field. Though such invocations are not universal, and though certain other scholars caution against it, the practice is nonetheless evident.

Of course, legal scholarship is not determinative of international law, and its effects on guiding State conduct or the workings of international organizations are by definition limited. Still, international-law scholarship — often referenced by courts, regularly relied upon in legal memoranda by government lawyers and those working in international organizations, and featured in reports by think tanks and advocacy groups — may ultimately affect the development and application of both treaties and custom. Indeed, recall that the ICJ Statute expressly treats the writings of certain legal publicists as subsidiary means for the determination of rules of law.[339]

Currently, there are major debates in scholarship and among practitioners as to whether fundamental aspects of the jus ad bellum field are developing. As demonstrated in this paper, silence appears to play a role in how these debates are constructed, which voices are heard, and which perspectives are seen as influencing the trajectories. Legal scholarship has played a key role in framing, reflecting, and amplifying this debate.

The questions of what silence means as a matter of international law and under what conditions it may and should be relied upon merit closer attention and discussion. Silence — whether expressly acknowledged or not, and whether intended or not — seems to be playing a role in the identification, formation, modification, and termination of treaty law and customary international law. This reliance on silence has the capacity to shape and develop international law and influence individual States, even where other States do not intend for their lack of a response to play such a role. If that is the case, States that are concerned about existing jus ad bellum, or about how that law may be developing, may therefore wish to consider the contexts in which they speak out and those in which they remain silent.

States, of course, cannot choose whether or not to speak out if they are unaware of particular positions that might merit a response. At the very least, therefore, States should, in our view, be made more easily, directly, and systematically aware of communications to the Security Council regarding the use of force as well as the Council’s and other States’ responses (or lack of responses) to those communications.

[339]. See ICJ Statute art. 38(1)(d).