Is Nuclear Weapons Law Stopping the Nukes?

Editors’ Note: This post draws upon the book, The Law on Nuclear Weapons: An International Commentary edited by the authors and published in 2025 by Edward Elgar.

It is always difficult to know for sure why political leaders and senior members of the armed forces decide strategic issues in the way they do. They may give speeches or interviews, publish memoires and articles in newspapers, but the thought processes that directed their action (or inaction) tend to remain inaccessibly locked inside their minds. The tendency rather is to consider the events, delivered speeches, interviews and so on, and to draw conclusions.

In that sense, the relative absence of direct armed conflict between nuclear-armed States during the last 80 years is noted to coincide with their possession of nuclear weapons during that period, and some kind of causal relationship is assumed by those who favour nuclear deterrence policies. The reference to “relative” absence is, of course, deliberate given, for example, the long-standing and at times violent dispute between India and Pakistan over Kashmir, as exemplified most recently between 6 and 10 May 2025. Nuclear prohibitionists would, however, dispute such a causal relationship.

What is undeniable is that the law that regulates the resort to the use of force, the key elements of which are to be found in Articles 2(4) and 51 of the UN Charter, seem to have had a sobering effect on those with the unenviable potential responsibility of deciding whether events demand a nuclear response. While it is neither necessary nor appropriate in this brief post to “name names,” readers will have noted that nuclear weapons have gained a higher and rather uncomfortable profile due to relevant statements issued by and on behalf of certain political leaders.

Notwithstanding the statements and headlines, mercifully, the nukes have stayed in their silos. Was it the “madness of mutual assured destruction,” the fear that a post-nuclear-war world might not be worth living in, or the proposition agreed in the aftermath of the Second World War, prohibiting both the threat and the use of force, that persuaded the pivotal actors not to send the codes?

Connecting the Strategic with the Legal Logic Behind Deterrence

The authors of this short post recognise that the UN Charter prohibitions have by no means been adhered to universally. Conventional warfare has not been prevented and nuclear-armed States are among those that have breached those customary provisions fashioned in the aftermath of the most awful orgy of multinational bloodletting. Maybe those rules weigh more heavily on those in power than the rest of us perhaps imagine.

While the political leadership, particularly in democratic States, will always seek to better the lot of their own nations—if need be, at the expense of other States—they tend to hesitate to do so by engaging in manifest breaches of international law. Take former UK Prime Minister Tony Blair, who appeared observably keen to receive supportive legal advice from the Attorney-General at the time, Lord Goldsmith, before finally agreeing to join U.S. President George W. Bush in the 2003 invasion of Iraq. Legacy focuses the minds of the powerful, and a democratic leader is unlikely to seek a legacy that is tarnished by an unlawful act that consigns millions to an early grave.

The process that led to the publication of The Law on Nuclear Weapons: An International Commentary involved the participation of a panel of experts. This included experts from nuclear weapon States, those from nuclear umbrella States that rely in part for their security on their allies’ possession of nuclear weapons, and those from States that assert that such weapons are inherently unlawful. The legal authority of the resulting text stems from the fact that experts with such diverse perspectives were prepared to endorse its publication, focussing as the book does on the legal rules that must underpin nuclear command, control, and communications arrangements by nuclear weapon States.

Customary Framework and Points of Contention

The detonation of two atom bombs in Japan in 1945 clearly demonstrated the unique levels of killing and destruction that the use of a nuclear weapon would inflict. The blast wave, the heat, the fire, the nuclear contamination, the consequent illness and deaths, are all likely to be very extensive indeed. This immediately causes one to wonder how the potential use of nuclear weapons can possibly be consistent with the “cardinal and intransgressible” principle of distinction that lies at the very core of the law of armed conflict. Indeed, if the definition of indiscriminate attacks as set forth in Article 51(4) of Additional Protocol I is accepted as reflecting customary law, one is driven to the conclusion that any nuclear attack would inevitably be indiscriminate in nature and therefore breach international law.

The 73 States that are party to the Treaty on the Prohibition of Nuclear Weapons and the additional 21 States that have signed it clearly take that view, as do the States that are party to the treaties establishing Nuclear Weapon Free Zones in Latin America and the Caribbean, the South Pacific, South-East Asia, Africa and Central Asia. It should also be recalled that the stationing of such weapons in outer space and on the seabed is prohibited by specific provisions. There are likely to be other States which, though not necessarily party to such treaty arrangements, consider nuclear weapons to be fundamentally unlawful.

There are, however, a number of States that are recognised internationally as possessing nuclear weapons. These States include the five permanent members of the UN Security Council (P5), India, Pakistan, Israel, and North Korea. Those States maintain nuclear deterrence policies based on their possession, ability, and implied willingness in extreme circumstances to employ such weapons, casting doubt on the existence of a general international practice accepted as law prohibiting nuclear weapons as such.

This inherent controversy between States that consider nuclear weapons to be inherently unlawful and those that point to an absence of such a general practice is one of the key divisions reflected in the book. While the International Court of Justice during the mid-1990s famously produced a non liquet advisory opinion that was heavily criticised, there can be no certainty that, were the legality of nuclear weapons to be considered again by the Court, a different outcome would be achieved, not least because of the same international controversy.

Disarmament or Non-Proliferation: Treaty-Based Controversy

So, if customary law is a matter of debate, the provisions of treaty law take on greater significance. Here again, however, there is controversy as to which of the key treaty regimes is of greatest value: the Non-Proliferation Treaty (NPT); or the Treaty on the Prohibition of Nuclear Weapons (TPNW). The focus of the former, as its name makes clear, is the prevention of proliferation. According to the regime set forth in Articles 1 and 2 of the treaty, nuclear-weapon States and non-nuclear-weapon States are prohibited from either transferring or receiving the transfer of nuclear weapons or other nuclear explosive devices.

The TPNW is an arms control treaty that prohibits the possession, stockpiling, transfer, use, etc. of nuclear weapons. Its prescriptive provisions are such that nuclear-weapon States seem unlikely to become party to the treaty. At the time of writing, no such State and no nuclear umbrella State has yet become party.

NATO and certain other States have issued statements formally rejecting the TPNW approach and expressing their preference for the non-proliferation regime set forth in the NPT. The argument is that the NPT has been successful in limiting the spread of nuclear weapons, the contention being that absent the NPT more States would have acquired the technology. The implied view is that preventing proliferation is the preferred approach given that the technology exists and cannot be uninvented. This argument, however, involves a certain degree of “cherry-picking,” when one considers the Article VI NPT obligation of States party to “negotiations in good faith on effective measures relating to cessation of the nuclear arms race at an early date and to nuclear disarmament, and on a treaty on general and complete disarmament under strict and effective international control.”

It is the observable failure of nuclear-weapon States to implement this obligation that seems to have led a number of non-nuclear-weapon States to negotiate and adopt the TPNW. In a sense, this controversy between States that prefer the TPNW ban and those that point to what they see as the relative success of the NPT is simply another manifestation of the same controversy as that noted earlier in the context of customary law. Both sources of law are riven by the same difference of view, and so long as no nuclear weapon States become party to the TPNW, it seems likely that the treaty that aims to rid the world of nuclear weapons will not see the peaceful destruction of a single weapon.

Concluding Thoughts

In January 2022, the P5 States issued a Joint Declaration in which they considered “the avoidance of war between Nuclear-Weapon States and the reduction of strategic risks as [their] foremost responsibilities.” They noted that “a nuclear war cannot be won and must never be fought,” and emphasised “the importance of preserving and complying with [their] bilateral and multilateral non-proliferation, disarmament, and arms control agreements and commitments.” Perhaps not all of the leaders who participated in the Declaration did so with an equal degree of sincerity.

Nevertheless, one might suggest that the making of the Declaration was, on balance, a good thing and that its text may reflect a deeper understanding that factually influences the actions of these influential individuals. It is, after all, one thing to “rattle the sabre” by making threats as to the use of nuclear weapons and quite another to use them.

The fundamental difference of perspective that has been discussed in this post is among the many issues underpinning the discussion of nuclear weapons law in The Law on Nuclear Weapons: An International Commentary. We, as joint editors, commend the willingness of the international panel of experts who reflected this diversity of views to agree to associate themselves with the book’s publication. We very much hope that it will be of use to those involved in nuclear command, control, and communications activities and to all of those who are otherwise involved in, or interested in, matters associated with nuclear weapons, whether from a legal, political, policy or other standpoint.

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Air Commodore William H. Boothby retired as Deputy Director of Royal Air Force Legal Services in July 2011. He is Honorary Professor at the Australian National University and also teaches at the University of Southern Denmark and at the Geneva Centre for Security Policy.

Wolff Heintschel von Heinegg holds the Chair of Public Law, in particular Public International law, European Law and Foreign Constitutional Law at the Europa-Universität Viadrina in Frankfurt (Oder), Germany.

The views expressed are those of the authors, 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: Airman 1st Class Jesse Lopez