Belligerent Reprisals Series – Enforcement, Reciprocity, and the Elusive NIAC Dimension

Editors’ note: This post is part of a series related to Francesco Romani’s book “Belligerent Reprisals from Enforcement to Reciprocity” published by Cambridge University Press.  

Few institutions in international humanitarian law (IHL) arouse as much unease as belligerent reprisals. This unease stems from the tension between a legal order that claims adherence to humanity and the unconditionality of its core rules on the one hand, and the stubborn reality of armed conflict, where reciprocity and retaliation continue to shape behaviour, on the other. Francesco Romani’s thoughtful post in this symposium, and his recently published book seek to recast our understanding of belligerent reprisals. He argues that their purpose has been unduly reduced to enforcement, a means of coercing the adversary into compliance, and that a fuller appreciation of their function must look to reciprocity, equality of arms, and the negotiation of standards of conduct between parties to an armed conflict.

Romani’s reconceptualization is stimulating and provocative. Yet, as with all attempts to reframe foundational concepts, it raises difficult questions. In this post I offer two sets of reflections. First, I question both the feasibility and the desirability of replacing the enforcement paradigm of belligerent reprisals with a framework focused on reciprocity and parity between belligerent parties. Second, I turn to the thorny issue of belligerent reprisals in non-international armed conflicts (NIAC), which I explored in my own 2014 article. Here, Romani’s proposal runs into additional obstacles, for the very applicability of reprisals in NIAC remains contested and uncertain, and his attempts to establish a legal basis for their use are not entirely convincing.

From Enforcement to Reciprocity? A Necessary but Risky Move

Romani reminds us that the current IHL mainstream conceives belligerent reprisals almost exclusively as an enforcement tool. The International Committee of the Red Cross (ICRC)’s commentary to Rule 145 of its Customary IHL Study states unequivocally that belligerent reprisals may be taken “only for the purpose of inducing the adversary to comply with the law.” This is why they have traditionally been modelled on peacetime reprisals (countermeasures) and have relied on the conditions used in that context: proportionality, subsidiarity, and temporariness are all meant to ensure that a prima facie violation of IHL serves solely to restore legality.

Romani challenges this narrative on two grounds. Empirically, he notes that parties to armed conflicts themselves often invoke purposes other than enforcement, such as punishment, deterrence, rebalancing equality of arms, or clarifying the rules of engagement. Conceptually, he suggests that understanding belligerent reprisals through reciprocity captures their true function much better: not coercion or enforcement, but the preservation of equality and parity between parties to an armed conflict. According to Romani, reprisals are less about ensuring compliance with pre-existing legal rules violated by one belligerent, and more about negotiating the law-in-action during hostilities. In his own words, “belligerent reprisals aim at re-calibrating the legal relationship between parties to an armed conflict and at ensuring parity of arms both in a formal and in a substantive sense” (p. 11).

There is much merit in this diagnosis. Certainly, the enforcement paradigm has always been somewhat simplistic. It presupposes that legal rules are clear, that violations of such rules can be unambiguously identified, and that belligerent reprisals are a rational and efficient tool to induce compliance. Reality is, however, far less orderly. Armed conflicts are characterized by contested interpretations, mistrust, and asymmetric capacities. To insist that belligerent reprisals can only be about enforcing pre-existing norms risks turning a blind eye to how belligerents use them in practice.

And yet, Romani’s proposal leaves some unease. Foregrounding belligerent reprisals in reciprocity and equality of arms risks validating precisely the logic that IHL has constantly sought to tame. While reciprocity may be an unavoidable sociological reality, elevating it to a normative principle that justifies otherwise prohibited conduct is problematic. Rather than providing order, it risks eroding the critical distinction between lawful reprisals and unlawful vengeance, between juridical self-help and indiscriminate retaliation.

For decades, IHL has tried, imperfectly but steadily, to insulate its core principles and rules from the effects of reciprocity. The Geneva Conventions consistently reaffirm that obligations enshrined in them apply “in all circumstances.” International tribunals have underscored the absolute and non-derogable character of the rules prohibiting attacks on and violence again certain persons and objects. If belligerent reprisals are reconceived not as reluctant enforcement tools but as mechanisms to recalibrate parity, the danger is that the fragile wall built around humanitarian guarantees may crack and, in fact, become meaningless.

Romani is aware of these risks, but his proposal does not fully address them. By suggesting that reprisals serve to “negotiate” standards of conduct, he implicitly accepts that the scope of humanitarian protection afforded to victims of armed conflicts is subject to real-time bargaining between belligerents. This is a bold yet deeply troubling position. If IHL ultimately depends on what parties are willing or compelled to accept under fire, its universal and unconditional character is fundamentally compromised. Such an approach threatens not only individual rules of IHL but also the very rationale for maintaining a legal framework to regulate the conduct of parties to armed conflict.

Belligerent Reprisals in NIAC: A Cautious Approach

These concerns become even more pressing once we shift focus from international armed conflict (IAC) to NIAC. In my own article on the subject, I outlined three approaches that dominate the debate: a) the extra-legal approach, which denies the applicability of belligerent reprisals in NIAC altogether, treating them as an inter-State tool; b) the permissive approach, which affirms their applicability without legal limits; and c) the restrictive approach, which allows for belligerent reprisals in NIAC but insists that they remain bound by legal constraints, whether drawn from Common Article 3, Additional Protocol II, or customary IHL.

Case law from the International Criminal Tribunal for the former Yugoslavia (notably Martić and Kupreškić) points in the restrictive direction, treating belligerent reprisals as in principle available in NIAC but subject to strict limits, especially the prohibition of reprisals against civilians. The ICRC in its Study on Customary IHL and other outputs, by contrast, has oscillated between extra-legal and restrictive positions, unwilling to recognize the applicability of belligerent reprisals in NIAC but also unwilling to leave the door open to unregulated retaliation. Scholarship, too, remains divided.

My conclusion was cautious. For now (or for then, back in 2014), belligerent reprisals in NIAC appear inapplicable. Yet certain developments hint at a possible evolution. Some treaty provisions on belligerent reprisals, for instance, Article 3(7) of the amended Protocol II to the 1980 Convention on Certain Conventional Weapons, seem to apply both in IAC and NIAC, though their drafting history leaves room for doubt. Customary law offers little clarity. Practice is sparse, opinio juris remains inconclusive, and much of the evidence stems from IAC rather than NIAC. In the end, the current state of legal regulation can best be described as unsettled, and we must approach with great caution any move toward recognizing reprisals in NIAC.

Romani takes a different approach. This reciprocity-based reconceptualization of belligerent reprisals leads him to a more accommodating stance. He argues that belligerent reprisals in NIAC cannot be considered inapplicable because there is an important role for them to play as a mechanism of recognition and parity, thereby helping to rebalance the relationship between unequal parties: States on one side and non-State armed opposition group(s) on the other. He also grounds this argument inductively, drawing on International Law Commission debates, UN reports, and statements by armed groups, which in his reading demonstrate that reprisals are invoked and practiced in NIAC, albeit often in ambiguous or informal ways.

This account is coherent with Romani’s broader reconceptualization: if belligerent reprisals are less about enforcement and more about reciprocity, then it makes sense to extend them to NIAC as tools of recognition and parity. Yet, as already noted, this reconceptualization is problematic. By grounding reprisals in reciprocity, it risks putting into question one of the central achievements of modern IHL: the effort to insulate fundamental protections from the tit-for-tat of battlefield bargaining. Reciprocity may be an unavoidable part of reality but turning it into a normative principle undermines the claim that IHL applies in all circumstances, regardless of the conduct of the adversary.

This challenge is particularly acute in NIAC settings. Reciprocity in NIAC lacks the structural safeguards present in IAC. There is no framework of sovereign equality, no established doctrine holding armed opposition groups as such responsible, and no effective institutional mechanisms to regulate or review reciprocal actions. Consequently, the regulation of NIAC has always been narrower and more cautious than that of IAC. States have deliberately withheld certain mechanisms such as Protecting Powers or the International Humanitarian Fact-Finding Commission from NIAC. The same logic applies to belligerent reprisals (when) viewed as an enforcement tool: they are ill-suited to the asymmetry of actors and the limited legal personality of non-State armed groups. Introducing belligerent reprisals in this context would effectively grant such groups prerogatives that States have long resisted.

Moreover, even if one were to adopt Romani’s re-description of reprisals as instruments of reciprocity rather than enforcement, the argument for their recognition in NIAC remains unpersuasive. There is already a form of equilibrium, albeit a negative one, in that neither side in NIAC is legally entitled to take reprisals. This prohibition reflects a deliberate balance. The law withholds the instrument altogether rather than risk its abuse in a context prone to escalation and cycles of violence. Romani’s reading of practice is also open to doubt. The evidence he cites, including UN reports, may reflect isolated incidents or rhetorical posturing rather than systematic, legally meaningful practice, which remains scarce and inconclusive. To introduce belligerent reprisals into the legal regulation of NIAC when empirical grounds for such a move are limited and inconsistent, and the theoretical underpinnings remain contentious, could be highly imprudent. It could undermine the integrity of the IHL framework without offering any obvious benefits.

Conclusion

Romani deserves credit for challenging the complacency of the enforcement paradigm. He is correct that belligerent reprisals have never been solely about coercion and that reciprocity continues to shape the practice of armed conflict. His call to confront this reality is both timely and valuable. Yet his move from description to prescription is far from self-evident. Reconceiving belligerent reprisals as instruments of reciprocity may illuminate one of their real life functions, but it carries serious normative risks. It threatens to erode the legal distinction between lawful reprisals and unlawful retaliation, and to destabilize the humanitarian protection that IHL seeks to guarantee.

These risks are especially acute in NIAC, where the legal status of belligerent reprisals remains unsettled and where the asymmetry of parties magnifies the potential for abuse. Non-State armed groups are not recognized as equal legal actors, accountability mechanisms are weak or absent, and there is no institutional framework capable of regulating tit-for-tat conduct. To legitimize reprisals in NIAC would be to trade fragile equilibrium for unpredictability, potentially opening the door to cycles of violence unregulated by IHL. Such a move lacks robust empirical support and a well-established theoretical foundation. Until a broader consensus emerges, we should approach with caution any attempt to justify retaliatory conduct as part of NIAC’s legal regulation, however theoretically refined.

In the end, the crossroads at which belligerent reprisals meet NIAC remains a test of IHL’s resilience. Reckoning with reciprocity is necessary, but to preserve the humanitarian project, IHL must maintain its principled boundaries. Only by doing so can it continue to protect the most vulnerable amid the chaos of armed conflict, rather than allowing norms to bend to the logic of the battlefield.

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Veronika Bílková is the head of the Centre for International Law at the Institute of International Relations, Prague, and an Associate Professor in the Faculty of Law of Charles University in Prague.

The views expressed are those of the author, and do not necessarily reflect the official position of the United States Military Academy, Department of the Army, or Department of Defense. 

Articles of War is a forum for professionals to share opinions and cultivate ideas. Articles of War does not screen articles to fit a particular editorial agenda, nor endorse or advocate material that is published. Authorship does not indicate affiliation with Articles of War, the Lieber Institute, or the United States Military Academy West Point.

Photo credit: U.S. Army, Sgt. Collin Mackall