Huge Nuclear Weapons Buildups: The Potential of Law To Address the Risks
4.24.2025
As New York lawyers, there are few things that attract our attention more than big consequential legal issues, issues that need work and development for the benefit of our clients, our families and our society. Occasionally, such issues come along that have the potential to be transformative and urgently need attention. One such constellation of issues – the lawfulness of the use of nuclear weapons and threat of such use – has been a focus of the New York State Bar Association’s International Section for several years. It is an issue of the greatest potential consequence, given the reality that the risk of nuclear weapons use, whether intentionally or through inadvertence or acts of terrorists, is high, even higher than during the Cold War.
With the fall of the Berlin Wall in 1989 and the collapse of the Soviet Union shortly thereafter, it seemed that nuclear weapons issues had receded, and their risks were a thing of the past. Yet, alas, that was not the case. Even during the period between the end of the Cold War and the more recent recurrence of international strife around Russia’s invasion of Ukraine and China’s nuclear weapons buildup, the United States never took much of a break. We kept building up our nuclear weapons capabilities with a fundamental shift from an attempt to ensure mutual security, which had been our approach with the Soviet Union by the end of the Cold War, to one of securing nuclear hegemony.
Now, the United States has embarked on a $1.5+ trillion nuclear weapons modernization[1] with an even greater costs likely,[2] and Russia and China are engaged in their own expansions of their nuclear arsenals, albeit at a lower level.[3] Moreover, Russia, with Vladimir Putin’s repeated threats to use nuclear weapons in Ukraine, has extended nuclear deterrence beyond its erstwhile posture as a defensive policy to one supporting overt aggression.
Starting in 2020, the International Section conducted several conferences, the third of which was held on Jan. 30, where we discussed nuclear weapons from the perspectives of stakeholders across the spectrum of policy and legal views on the matter, and, inevitably, looked at the broader question of whether international law matters. The proceedings of those earlier conferences were published in special editions by the Fordham International Law Journal[4] and the Georgetown Journal of International Law.[5] The Georgetown Journal will publish the proceedings of the recent conference.
Believing that international law matters can take a leap of faith, given contemporary events: Russia’s actions in Ukraine, the current Israeli/Hamas conflict and related activities, Iran’s nuclear aspirations and support of terrorism, North Korea’s nuclear buildup, the U.S. invasion of Iraq and the Trump administration’s approach to policy and legal matters. Yet there are grounds for believing international law, including the law of armed conflict, has continuing relevance. As Yale Law School Professor Oona Hathaway described in her keynote at NYSBA’s 2023 conference in this series, international condemnation for Russia’s transgressions has been broad and loud, Ukraine has been greatly assisted by the West in its opposition to the Russian aggression, and there have been prosecutions by the International Criminal Court, along with an arrest warrant for Putin.[6] And, in any event, as seems obvious, the existence of crime does not vitiate applicable law, and there is the hope of reconstitution of a more normal and hopeful world order.
The U.S. itself has broadly and consistently recognized the importance of international law and its applicability to the threat and use of nuclear weapons.[7] The Department of Defense has issued, and periodically updates, its Law of War Manual, a detailed exposition of international law as concerns the use of force.[8] The Biden administration, in its 2022 Nuclear Policy Review, cited that manual as an authoritative source of law as to such matters.[9]
But what about other countries? Will countries such as Russia, China, Iran and North Korea comply with the law of armed conflict, or is it a fool’s errand to expect such compliance? Ironically, perhaps the very destructiveness of nuclear weapons helps here. Credible modeling now tells us that widescale nuclear war between the U.S. and Russia could cause over 5 billion deaths.[10] Mutual assured destruction as an element of nuclear deterrence is not a mere figure of speech. At some point, it seems reasonable to hope that, with appropriate messaging and pressure, a sense of national, if not human, survival can kick in, making leaders of nuclear weapons states realize that, as we’ve heard from so many U.S., Russian and other leaders, nuclear war cannot be won and must never be fought.[11]
Speakers at the International Section’s conferences on nuclear weapons and international law have included senior U.S. government officials and military officers, past and present, with authority for U.S. nuclear weapons policy, including JAG lawyers with responsibility for legal advice as to the use of such weapons, and academic and activist leaders, with some speakers supporting and some challenging the lawfulness of the United States’ nuclear weapons policies and war plans under contemporary law.
What has emerged is that, while there is consensus by the U.S. and other nuclear weapons states that there is a robust body of international law that governs the lawfulness of the threat and use of nuclear weapons, and substantial consensus on the rules of that body of law, there are many issues as to the application of that body of law to the facts as to effects of such weapons.
It is on this issue of application that the lawfulness of the U.S. policy of nuclear deterrence and its war plans turns. If the U.S. is correct in its views on the matter, its policy of deterrence and war plans may pass legal muster. If, as some critics assert, the U.S., in order to protect its policy of deterrence, is distorting and misapplying the law, its policies and plans in the area are unlawful and potentially threaten war crimes.
The basic rules of the road are recognized by supporters and critics of the status quo.[12]
The rule of distinction provides that only weapons whose effects can distinguish between combatants and civilians may lawfully be used; indiscriminate weapons, such as chemical and biological weapons, may not be used. The rule of proportionality provides that weapons whose effects on civilians would be disproportionate to the direct and concrete military benefit of the weapons use may not lawfully be used. The rule of necessity requires that combatants only use such a level of force as is necessary to address the military objective at hand and that, where a lower level of weapon could address the military objective, it be used, and that superfluous or unnecessary damage or injury not be caused. The rule of precaution requires that states take reasonable precautions to assure that their weapons acquisitions, inventories, personnel and actual uses of weapons comply with applicable law. Each of these rules prohibits the use of weapons whose effects cannot be controlled.
Where is the rub then? It seems evident that nuclear weapons – with radioactive fallout and other effects that threaten not only millions but billions of civilians – cannot comply with the rules of distinction or proportionality, and that policies and war plans that threaten use of such weapons cannot comply with the rule of precaution. And that nuclear weapons could not lawfully be used in circumstances where today’s extraordinarily accurate and destructive conventional weapons would be able to address the military need at hand.
The rub, again, is in the application. If the views of critics of our practices in this regard have merit, the ways in which the United States narrows the scope of these rules when it comes to nuclear weapons greatly distorts the rules. Following are salient examples.
What are the consequences if, in applying the rules of distinction and proportionality, as the U.S. has suggested, one only considers whether the nuclear weapons whose use is being considered will hit the target, without regard to whether the radioactive fallout, nuclear winter or other effects that threaten millions or even billions of deaths will be limited to the target area? Or what if decision-makers don’t consider effects that can’t be quantified or modeled in detail and hence that are uncertain as to their extent or landing points, but nonetheless are foreseeable and even inevitable?
Or what if all that is considered, in conducting the legal analysis, are the potential effects of weapons uses that the civilian or military decision-makers regard as likely or highly likely or even as inevitable – and they don’t consider foreseeable effects that may occur that would be far more destructive and far-reaching than the limited types of effects on which the decision-makers are focusing?
Or what if the nuclear weapons use under consideration is a low-yield one against a remote target, but foreseeably will likely precipitate a nuclear counterattack by the target and potential escalation, with far greater humanitarian consequences?
Given credible estimates that nuclear war between the U.S. and Russia could cause billions of deaths, such narrow interpretations of the scope of the applicable rules, when it comes to potential uses of nuclear weapons, are consequential. Yet – and here’s the invitation for us lawyers – these issues have been under-analyzed, and U.S. policies and plans in the area under-scrutinized, as concerns compliance with law. Whether the defenders or critics of the status quo are right in the context of the actual facts requires broader and deeper objective analysis by legal experts in the field and by policy and technical experts, if concerns about our current policies and war plans are to be addressed.
As U.S. District Judge Shira Scheindlin (Ret.) noted in her comments at the International Section’s Jan. 30 conference, law grows and develops from experience – from the progression of statutory and case law.[13] As to the law of armed conflict generally, the world, unfortunately, has seen continuous conventional warfare throughout the modern era, contributing to the development of that body of law. However, with respect to nuclear weapons, we, fortunately – indeed, luckily – have not had experience since the U.S.’s use of such weapons in Hiroshima and Nagasaki.
Given this fortunate gap in experience, does it not seem that anything credible we can do to contribute to the development and support of this law and to compliance with it is important? For example, what are the consequences as to the appropriateness of our national policies, if the above limited applications by the U.S. of the rules of distinction, proportionality, necessity and precaution are inconsistent with the actual requirements of such rules? What if, in assessing the lawfulness of uses of nuclear weapons under consideration, decision-makers are legally required to consider all foreseeable non-speculative consequences of such potential uses?
The question of the level of certainty a decision-maker needs to have before considering the use of a nuclear weapon in any given situation is another such question. In conventional warfare, the law of armed conflict within reason gives considerable leeway to decision-makers as to military strikes and weapons they use in the throes of war. However, does such deference, such a deferential mode of legal assessment, make sense – is it reasonable? As to nuclear weapons, with their exponentially greater consequences, potentially imperiling the continuation of the human race?
It appears that U.S. lawyers haven’t really changed this approach of deference to individual decision-makers, as concerns the training of our personnel and planning for the use of nuclear weapons. Doesn’t this area need to be re-thought? Do we want to leave such judgments to the reactions under stress of a limited number of individual decision-makers, even the U.S. president?
These are the types of questions about the lawfulness of nuclear weapons threat and use that, as the International Section’s recent conferences have highlighted, cry out for objective study and analysis by serious and insightful lawyers – and then for policy initiatives to foster international compliance with applicable law, compliance motivated by the existential nature of the risks of the status quo.
There’s a further basis for the proposition that law matters, as concerns the lawfulness of nuclear weapons threat and use: the notion that law offers perhaps a better, more potentially effective approach than policy for achieving the delegitimization of nuclear weapons and their abolition.
Policy’s limitations as a basis for deep progress as to these issues flow from the broadly held view of the policy of deterrence as essentially safe – as essentially a policy where all we must do is threaten potential enemies with annihilation, with assured destruction, and we can avoid a hot war. That would be a pretty good bargain, right?
That’s not reality, of course: deterrence requires states to develop and maintain a robust ability and preparedness to actually use such weapons, to make the threat credible. It has led to the world’s huge arsenals of these weapons and generations of military trained and ready to launch them at a moment’s notice.
The collective denial of these realities and pretense that deterrence is only an unfortunate but necessary policy of threat likely means that the closest we can get through a policy approach to ameliorating nuclear weapons risks is arms control and crisis abatement, as happened during the Cold War.
With law, however, we have the potential to delegitimize nuclear weapons, as happened with biological[14] and chemical[15] weapons and, to a considerable extent, with landmines.[16]
The salience of this situation for our purposes, as lawyers, is that there are legal issues here that are complex, compelling and challenging – and, most essentially, that cry out for objective attention and development. With the demise of the Soviet Union, they fell off the front burner, but they are again with us.
We can’t discount the reality that there are bad actors out there and that passions, ingrained attitudes, nationalism, atavism and the whole gamut of human and societal fragilities and irrationalities may doom the venture. Yet there is also that human instinct toward survival and even goodness, and at least the potential for the individual and societal dark side to give way to our better instincts – instincts that should kick in if the warnings of not millions but billions of deaths that could result from nuclear war are heeded. We can hope – and even expect – that there will be better times and that it well behooves us to lay the groundwork toward building a true regime of law that will be ready when circumstances permit.
Whether an effort by the U.S., if we were to reexamine this area and attempt to bring the rest of the world around to a deeper commitment to legal requirements and instincts of survival, with an appropriately designed verification regime – whether such efforts would be successful is, of course, unknown. What does seem clear is that, if the U.S. doesn’t step up on this existential challenge, no other state will, and the delegitimization of nuclear weapons will not happen – with the result that these existential risks of the destruction of human life will continue and likely worsen, with the very real prospect our luck will run out.
Charles J. Moxley, Jr. is principal at MoxleyADR. He is co-chair of the Commercial and Federal Litigation Section’s Committee on Arbitration and ADR, former chair of the Dispute Resolution Section, and active in the International Section. He is the author of “Nuclear Weapons and International Law: Existential Risks of Nuclear War and Deterrence Through a Legal Lens.” Moxley is an adjunct professor of law at Fordham Law School and the distinguished ADR professional in residence at the Benjamin N. Cardozo School of Law. He has taught nuclear weapons law at Fordham for over 20 years.
Endnotes:
[1] Xiaodon Liang, U.S. Nuclear Modernization Programs, Arms Control Ass’n, Aug. 2024, https://www.armscontrol.org/factsheets/USNuclearModernization.
[2] Hans M. Kristensen, Matt Korda, Eliana Johns, and Mackenzie Knight, United States Nuclear Weapons, 2025, Bulletin of the Atomic Scientists, 2025, 81(1): 53-79. DOI: https://doi.org/10.1080/00963402.2024.2441624.
[3] Int’l Campaign to Abolish Nuclear Weapons, Surge: 2023 Global Nuclear Weapons Spending, June 2024, https://assets.nationbuilder.com/ican/pages/4079/attachments/original/1718371132/Spending_Report_2024_Singles_Digital.pdf?1718371132.
[4] Proceedings of Conf., Nuclear Weapons and International Law 2020, 45 Fordham Int’l L. Journal (Spec. Ed.) May 2022, https://static1.squarespace.com/static/5b394cb9365f029282c3590a/t/6287dbf9f2fb542c38b72f08/1653070843043/45_Special+Edition_Combined.pdf.
[5] Proceedings of Conf., Nuclear Weapons and International Law: Renewed Imperative in Light of the Russian Invasion of Ukraine, 55 Geo. Journal of Int’l L., Nov. 8, 2023, https://www.law.georgetown.edu/international-law-journal/on-line/.
[6] Oona Hathaway, Keynote Address at NYSBA’s 2023 conference, “Nuclear Weapons and International Law: The Renewed Imperative in Light of the Ukraine War,” Nov. 8, 2023, https://nysba.org/events/nuclear-weapons-and-international-law-the-renewed-imperative-in-light-of-the-russian-invasion-of-ukraine/.
[7] See, e.g., International Court of Justice Proceeding: Advisory Opinion Requested by the U.N. General Assembly on the Legality of the Threat or Use of Nuclear Weapons, Written Statement of the United States, at 2, June 20, 1995 (prepared by Conrad K. Harper, Michael J. Matheson, Bruce C. Rashkow, and John H. McNeill on behalf of the United States).
[8] Dep’t Def., Department of Defense Law of War Manual § 6.18 at 416-17, June 2015, updated July 2023, https://media.defense.gov/2023/Jul/31/2003271432/-1/-1/0/DOD-LAW-OF-WAR-MANUAL-JUNE-2015-UPDATED-JULY%202023.PDF [hereinafter, “DoD Law of War Manual”].
[9] U.S. Dep’t Def., Nuclear Posture Review (2022) 1, 8, https://apps.dtic.mil/sti/trecms/pdf/AD1183539.pdf.
[10] Lili Xia et al., Global Food Insecurity and Famine From Reduced Crop, Marine Fishery and Livestock Production Due to Climate Disruption From Nuclear War Soot Injection, 3 Nature Food, 586, 587 at Table 1, Aug. 2022, https://www.nature.com/articles/s43016-022-00573-0.
[11] George P. Shultz, The War That Must Never Be Fought, Hoover Institution, March 12, 2015, https://www.hoover.org/research/war-must-never-be-fought-0.
[12] Details as to the applicable rules and issues concerning them are discussed in Charles J. Moxley, Nuclear Weapons and International Law: Existential Risks of Nuclear War and Deterrence through a Legal Lens (Rowan & Littlefield, 2024), in Chapters 1, 2, 27, and 28.
[13] The proceedings of this conference will be published by the Georgetown Journal of International Law. See Recording: Nuclear Weapons and International Law 2025: Nuclear Risks Through a Legal Lens, N.Y. St. Bar Ass’n, Jan. 20, 2025, https://nysba.org/events/nuclear-weapons-and-international-law-the-renewed-imperative-in-light-of-the-russian-invasion-of-ukraine/.
[14] DoD Law of War Manual, supra note 8, at § 6.9 at 382-85.
[15] DoD Law of War Manual, supra note 8, at § 6.8 at 376; Convention on the Prohibition of the Development, Production, Stockpiling and Use of Chemical Weapons and on their Destruction, 1974 UNTS 45; 32 ILM 800 (Jan. 13, 1993).
[16] See United Nations, Convention on the Prohibition of the Use, Stockpiling, Production and Transfer of Anti-Personnel Mines on Their Destruction: Status, Treaty Collection (updated May 2, 2025), https://treaties.un.org/pages/ViewDetails.aspx?src=TREATY&mtdsg_no=XXVI-5&chapter=26&clang=_en.
