Legal and political myths of the Treaty on the Prohibition of Nuclear Weapons

The Treaty on the Prohibition of Nuclear Weapons (TPNW) is, by any measure, a major milestone in international law and nuclear security policy. It is the first treaty in history that categorically and permanently prohibits for all its parties the testing, possession, transfer, use, or threat of use of nuclear weapons, and that aims for universal participation. The treaty entered into force on January 22, 2021 and has already attracted 54 parties and an additional 32 signatories, although all the countries that possess nuclear weapons, along with their closest allies, have stayed away.

In this article, we take no position on the treaty’s substantive merits. The treaty’s proponents herald the agreement as a major accomplishment in the longstanding effort to eliminate all nuclear weapons and to keep the world free from this historic scourge. These humanitarian achievements would mark the eagerly-awaited fulfillment of the nuclear disarmament commitment contained in Article VI of the 1968 Nuclear Non-Proliferation Treaty (NPT). The TPNW could become a significant conceptual watershed, helping to stigmatize the continued possession of nuclear weapons and reenergizing the global effort to abolish them in a timely fashion.

On the other hand, the treaty’s critics observe that it has been joined—and for the foreseeable future likely will be joined—only by states that do not possess and have already legally foresworn nuclear weapons. The treaty will not, by itself, accomplish the destruction of even a single warhead.

Our attempt here is to place the Treaty on the Prohibition of Nuclear Weapons in its appropriate political and legal context, to identify a few of its signal accomplishments and shortcomings, and to address a series of sometimes-deliberate myths or mischaracterizations that have impeded careful analysis of the treaty’s place in the annals of disarmament efforts. We hope to sort out confusing or conflicting claims about the treaty without addressing questions regarding humanitarian issues, deterrence, and verification that have been discussed in detail elsewhere.

A network of treaties

The Treaty on the Prohibition of Nuclear Weapons is a remarkable, stand-alone instrument in a field already populated by a series of interrelated international agreements. The treaty’s parties are not required to join the Non-Proliferation Treaty, or to adhere to the 1996 Comprehensive Nuclear Test Ban Treaty, or to accept the Additional Protocol applicable to safeguards agreements with the International Atomic Energy Agency—all key multilateral bulwarks against the spread of nuclear weapons. In addition, many of the relevant states are also already parties to one of the regional nuclear-weapon-free-zone treaties that establish binding legal obligations that partially overlap those of the TPNW.

The original concept behind the Treaty on the Prohibition of Nuclear Weapons was that the negotiators would produce an integrated package of two legally-binding documents. The first would be a relatively brief instrument in which the world would declare that nuclear weapons are (or should be) illegal and that all existing nuclear weapons must be promptly eliminated. This would be followed by a second, much more detailed document, modeled after the 1993 Chemical Weapons Convention, that would establish procedures for the elimination of all such weapons, create an effective verification regime, define all relevant terms, and more. This approach would resemble many prior successful major arms control treaties.

What actually happened, however, was a short and efficient negotiating conference at the United Nations headquarters in New York in 2017 that melded these two documents into a single treaty. The negotiators established a firm, comprehensive, legal prohibition on nuclear weapons but deferred crucial technical details for later work by whoever eventually turned out to be the treaty’s parties. They appeared to assume that all or many of the states with nuclear weapons would join the deliberations. However, this was not to be. The result has been that all of the states with the most nuclear expertise—in particular, the United States and Russia with their decades of Strategic Arms Limitation Talks/Intermediate-range Nuclear Forces Treaty/Strategic Arms Reduction Treaty/New Strategic Arms Reduction Treaty experience—were unavailable to help design the crucial details of implementation. Those states, in fact, opposed the entire enterprise and have denounced the TPNW in its current form.

Aspirational or legally binding

Coming to grips with this situation, some advocates of the Treaty on the Prohibition of Nuclear Weapons have recognized that the document cannot accomplish its object and purpose without a dramatic change of heart by the five permanent members of the Security Council and the other nuclear weapons possessors. Accordingly, some proponents now say that the treaty is, in part, an “aspirational” document whose primary, immediate purpose is to shift the terms of the international debate about nuclear weapons from a dialogue about deterrence toward greater sensitivity to the humanitarian consequences of nuclear activities. As part of this process, the treaty aspires to pressure the nuclear weapons states to see the light. To borrow a phrase, it is to be taken seriously, but not literally.

Arms control treaties often emphasize lofty aspirations, such as by placing reference to longer-term goals in a preamble. To be sure, the Treaty on the Prohibition of Nuclear Weapons does have an unusually expansive preamble engaging in that sort of rhetoric. However, a document with so many legally binding provisions is not merely aspirational; it is legally actionable. The treaty’s awkward problem is that it was primarily drafted to apply to states with nuclear weapons, but all of its current parties are states without such weapons. Some have since suggested that the nuclear weapon states should, in response, draft their own parallel treaty that incorporates the provisions they identify as necessary to a more effective engagement. The legal confusion this process could generate is obvious.

A series of myths

Six legal and political myths surround the status and effects of the Treaty on the Prohibition of Nuclear Weapons. Like all good myths, these contain certain elements of truth. However, their overall effect is misleading, sometimes deliberately so, in pursuit of political advantage. The first three myths have been propagated by the treaty’s supporters while the last three are attributable to its opponents.

Myth 1: The Treaty on the Prohibition of Nuclear Weapons constitutes international law. This myth exemplifies the category of “true but inaccurate.” That is, as an international agreement concluded between states in written form and governed by international law, the document certainly fits the definition of a “treaty” under the Vienna Convention on the Law of Treaties, Article 2.1(a). In that sense, it constitutes binding international law. But that characterization is woefully incomplete without the important caveat that, like any other treaty, the TPNW is law only for the states that voluntarily agreed to join. It has no authority over the United States, Russia, China, or the other countries that have elected to stay away.

Article 34 of the Vienna Convention on the Law of Treaties makes explicit the general rule that “A treaty does not create either obligations or rights for a third State without its consent.” This means that while 54 states have joined the TPNW and adopted its full slate of legal obligations, the vast majority of the world’s countries—representing an even vaster majority of the world’s population—are legally immune from it.

For comparison, it could be stated that any bilateral treaty—such as the 2010 New START between the United States and Russia—constitutes international law. For those two participants, that characterization is completely true. But adding “for those states” to this sentence would describe the legal situation more accurately. In like manner, multilateral treaties such as the NPT are binding international law, but their restrictions are legally irrelevant to those states that, in the exercise of their national sovereignty, have elected not to adhere. Implying otherwise is intellectually dishonest.

Myth 2: The contents of the Treaty on the Prohibition of Nuclear Weapons constitute (or will soon constitute) customary international law. Sometimes the contents of a treaty do pass into customary international law, thereby assuming a binding quality even for states that have opted out of the treaty. In particular, a multilateral law-making instrument that has been designed to attract widespread or even universal adherence and that does in fact win nearly that degree of support, can thereby generate or reflect new norms of customary international law.

In the realm of arms control, something of that sort probably happened with the 1967 Outer Space Treaty and the Chemical Weapons Convention. Much, if not all, of the substantive content of their respective ban provisions would now be regarded as applicable to all states, even beyond the significant numbers of states that have ratified or acceded to them. (It should be noted that the unwritten nature of customary international law inherently generates a degree of ambiguity about its applicability – there is often no authoritative mechanism for determining whether and when a particular rule becomes binding. Even with respect to these two treaties, it would be hard to prove that they reflect customary international law, though most informed observers would claim as much.)

The standard criteria defining customary international law focus on establishing and maintaining a longstanding, widespread pattern of concordant state behavior, undertaken out of a sense of legal obligation and accepted by the community of states. To be sure, there are plenty of indefinite terms in that definition, and there is often scope for debate, for example, about whether a pattern has been sufficiently “widespread” or “longstanding” to meet the test.

For the Treaty on the Prohibition of Nuclear Weapons, however, most would agree that the behavior of 54 states, together with a duration that started as recently as January 22, 2021, would be insufficient. This conclusion is especially inescapable since many of the nonparticipants have not been merely passively disengaged; they have been active in opposition, resisting the entire diplomatic initiative and rigidly declaring their objection to the treaty and its negotiation.

It is also generally accepted that in the articulation of a pattern of state behavior regarding customary international law, there is no principle of “one state, one vote.” That is, states that are especially active in the particular field, or that are specially affected by the putative rule, carry more weight. With nuclear weapons, all states are potentially affected in vital ways. However, the attitudes and actions of the five permanent members of the UN Security Council and the other countries that possess nuclear weapons cannot be ignored. All of those states have overtly opposed the treaty.

Finally, it should also be noted that any state may exempt itself from a rule of customary international law by positioning itself as a “persistent objector” (or “consistent dissenter”) from the norm. This opposition must be public and must be sustained from the outset. In the case of the Treaty on the Prohibition of Nuclear Weapons, the consistent, vigorous opposition from the United States and several others would surely qualify. Thus, even if the treaty were somehow deemed to have risen to the status of customary international law, many important states would have effectively exempted themselves from it.

Myth 3: The Treaty on the Prohibition of Nuclear Weapons constitutes an international norm that states should respect. Here, treaty advocates who realistically concede the first two points—that the TPNW has no legally binding force upon non-parties and that it does not constitute, and probably never will constitute, customary international law—retreat to a less strident form of argumentation. In this instance, they use a mélange of carefully chosen terms to suggest an importance that runs well beyond their real meaning.

The term “norm,” for example, is marvelously vague. Sometimes, it is used as a synonym for “rule” or “law.” Other times, it conveys a softer meaning, such as “principle” or “tradition.” Often it refers to a practice that has been hallowed by widespread respect, but whose violation results in social or political, rather than legal, stigma. In that latter sense, the Treaty on the Prohibition of Nuclear Weapons could be a candidate for a “norm” because the treaty entrepreneurs earnestly want additional states to behave in conformity with it and activists will attempt to persuade, cajole, entice, or pressure wavering states to join. But there is no international legal content to enforce that behavior.

Likewise, this myth expresses what states “should” do regarding the treaty, rather than relying upon the legally operative verb “shall.” And those who promote this myth call upon states to “respect” the treaty, rather than the tougher mandate to “obey” or “carry out” its terms. They sometimes denigrate the states that oppose the treaty as “outlaws” for acting in defiance of international standards of behavior.

All of this extravagant rhetoric is designed, like many other myths, to convey a seemingly stronger message than the underlying truth supports. States that have not joined the treaty have no obligation to uphold it. Advocates can call upon them to join or, short of joining, exhort them to respect and support it more abstractly. While these actions are a completely fair sort of political gamesmanship, there is no legal authority behind that ploy, and it is misleading to imply the existence of some quasi-lawful mandate. The Treaty on the Prohibition of Nuclear Weapons may help shift global consciousness by stigmatizing nuclear weapons with the kind of fervor previously attached to anti-personnel land mines or blinding lasers. The historical trend line may even point in that direction. However, that transformation has not yet occurred.

Myth 4: The Treaty on the Prohibition of Nuclear Weapons will undermine the NPT. Treaty opponents are just as prone to hyperbolic rhetoric as are the supporters. Here, as above, there is valid cause for legal attention. Article 30 of the Vienna Convention on the Law of Treaties addresses successive treaties relating to the same subject matter. In a nutshell, if states A, B, and C join treaty One, and then later, A and B (but not C) also join treaty Two addressing the same topic, the legal relationships among them can become complex. Between A and B, treaty Two will prevail. Between A and C, or between B and C, however, C still retains the right to insist upon the original agreement; C’s rights and obligations pursuant to treaty One are not affected by whatever new legal relationships may arise between A and B.

But this legal structure shows its teeth only when the two treaties are substantively inconsistent, when it would be difficult or impossible for the affected states to implement simultaneously all the overlapping provisions in good faith. In comparing the TPNW and the NPT, no such incompatibility is apparent. It would certainly be possible for a state to comply fully with both sets of obligations – in fact, the overall goals and the nitty-gritty obligations of the two instruments are quite harmonious. A state that joined both treaties would be required to continue to carry out its NPT obligations in full and, in addition, to undertake the further measures in pursuit of the Treaty on the Prohibition of Nuclear Weapons; it could readily comply with both sets of terms.

Still, the Treaty on the Prohibition of Nuclear Weapons imposes obligations on its parties that are significantly stricter than those of the NPT. For example, the newer instrument prohibits the “stationing, installation, or deployment” of nuclear weapons on a party’s territory—activities that the NPT permits, even for countries that are not themselves allowed to possess nuclear weapons. But the NPT certainly does not require a country to host another state’s nuclear weapons. So, a state that was party to both treaties could readily comply with both, simply by not allowing the stationing, installation, or deployment of nuclear weapons.

The Treaty on the Prohibition of Nuclear Weapons acknowledges this potential overlap of legal obligations. Article 18 provides that “(t)he implementation of this Treaty shall not prejudice obligations undertaken by States Parties with regard to existing international agreements, to which they are party, where those obligations are consistent with the Treaty.”

Indeed, in a larger political sense, the Treaty on the Prohibition of Nuclear Weapons does not undermine the NPT, but actively reinforces it. In particular, it adds pressure on nuclear-weapons states to comply more fully with their obligations under Article VI to negotiate in good faith on effective measures related to nuclear disarmament. That increased torque is one of the reasons why the nuclear-weapon-possessing states are so resistant to the TPNW. They do not simply dismiss it as legally irrelevant to them; they vigorously attack it because they accurately perceive it as a mechanism for rallying global activism in support of honest fidelity to the NPT. The nuclear weapons possessors are right to be apprehensive about growing support for the Treaty on the Prohibition of Nuclear Weapons—it challenges their traditional control over the disarmament dialogue and makes more visible their failure to date to redeem the Article VI obligations.

The concern that overly zealous advocacy for the Treaty on the Prohibition of Nuclear Weapons could politically weaken support for the NPT may be valid if proponents suggest that the newer treaty could replace the older one, or assert that the NPT has irretrievably failed, and should be superseded. But the nonproliferation and disarmament goals of both instruments are compatible and they should be viewed as harmonious.

In contrast, the Treaty on the Prohibition of Nuclear Weapons may be inconsistent with some states’ obligations under other treaties. Pursuant to the NATO treaty, for example, several European parties have agreed to host and share control over US nuclear weapons—activities the TPNW would prohibit. This incompatibility no doubt helps explain why the United States and countries that nestle beneath its nuclear deterrence “umbrella” are so antagonistic to the TPNW. Similarly, some of the nuclear sharing arrangements through the International Atomic Energy Agency may be called into question—but so far, no such problems have emerged.

Myth 5: The countries possessing nuclear weapons and their closest allies will never join the Treaty on the Prohibition of Nuclear Weapons. At the moment, this assertion may seem like a reasonably safe bet, but the concept of “never” connotes a very long time indeed. Who knows what future domestic political gyrations may occur in European, Asian, or other capitals?

To date, the “umbrella” countries, including the NATO allies, have been steadfast in giving only a cold shoulder to the Treaty on the Prohibition of Nuclear Weapons. However, the domestic political constituencies in several of them may be much more receptive to immediate steps toward nuclear abolition, and the “nuclear allergy” in Japan and elsewhere is profound, too.

The Netherlands broke the NATO solidarity in 2017 and participated in negotiating the Treaty on the Prohibition of Nuclear Weapons, though ultimately voting against adoption of the treaty text. In 2018, the Dutch parliament called upon the government to reexamine the treaty and attempt to increase support for it among NATO members. Belgium’s parliament also adopted a similar measure. At the same time, public opinion in both the Netherlands and Belgium runs overwhelmingly in favor of joining the treaty.

In politics, nothing is as permanent as change, and NATO’s democracies are ultimately susceptible to the will of the people. Again, perhaps that long-term vulnerability helps explain the rigidity with which the treaty’s opponents now proclaim that their states will “never” adhere, as if wishing to ensure a political future they cannot, in truth, guarantee.

Myth 6: The Treaty on the Prohibition of Nuclear Weapons will not accomplish anything. TPNW opponents have attempted to dismiss the treaty as a dead letter, asserting that their resolute resistance will prevent it from having any appreciable effect on the longstanding international dialog about nuclear weapons and international security policy.

However, even if the nuclear weapons-possessing states and their closest allies continue to abstain, the Treaty on the Prohibition of Nuclear Weapons can nonetheless exert a significant, prolonged effect on global affairs, and indeed it already has done so. The 1997 Ottawa Convention on anti-personnel land mines provides a vivid illustration of a multilateral agreement that has been consistently rejected by the United States and the other leading possessors of the weaponry, but that has irrevocably altered global attitudes toward, and practices with, the designated devices. Even without universal membership, the mine ban has fostered a new public rejection of the reviled weapons on humanitarian grounds, resulting in drastic reductions in the manufacturing, international transfer, and use of land mines, including by non-parties. The profound global stigmatization has shifted the debates about the acceptability of these weapons, strongly affecting public policy even in the holdout states.

There is, of course, no guarantee that the Treaty on the Prohibition of Nuclear Weapons can be similarly successful in inspiring a parallel public rejection of continued reliance upon nuclear weapons, but this experience provides a vivid reminder that we cannot measure the true impact of a new treaty solely by tabulating the number of its early ratifiers. The social and political consequences of the TPNW may turn out to be much more profound, in shifting the terms of the policy discussions toward humanitarian concerns and in instigating a popular groundswell toward abolition. Movement in that direction is already apparent, and the treaty could catalyze an even deeper, more lasting public commitment to that vital goal.

The Treaty on the Prohibition of Nuclear Weapons and the NPT

The relationship between the Treaty on the Prohibition of Nuclear Weapons and the NPT is of crucial importance, especially in view of the upcoming discussions at the 50^th anniversary NPT Review Conference, which was delayed twice by the pandemic and is now scheduled to convene in New York in August. The TPNW seems certain to be a major, controversial topic; it is important that the discussions of it be substantive and respectful. This exchange will be much more productive if all sides could agree in advance on the legal implications of the treaty and on the vocabulary that should be used to describe the current situation.

Unfortunately, some academics have publicly urged countries to withdraw from the NPT and join the Treaty on the Prohibition of Nuclear Weapons instead. We regard that posture as the height of irresponsible folly—the NPT remains a vital cornerstone of international security, and should not be jeopardized. A somewhat more moderate, but still specious, contention is that the TPNW will replace the NPT or render it redundant once enough countries join. This posture overlooks the broader writ of the NPT, including its contributions to nuclear safety and the sharing of the peaceful benefits of nuclear energy, all which have nothing to do with weapons capabilities.

No country needs to choose between the NPT and the Treaty on the Prohibition of Nuclear Weapons, as it is certainly feasible to adhere to both simultaneously. In our view, the states that possess nuclear weapons should not drag their feet in the pursuit of the abolition of nuclear weapons, and the states that have joined the TPNW should not abandon or denigrate the historical role of the NPT.

There are also other legal and political issues. One concerns the yet-to-be determined elimination and verification requirements. As the Treaty on the Prohibition of Nuclear Weapons is formulated, a country may not know what procedures it must carry out or what intrusive verification measures it must submit to until after agreeing to accept them. A “competent international authority” will determine these. It is unclear whether a country with nuclear weapons that joins the treaty will have a veto or even a vote in this body’s proceedings. Another possible legal problem arises from the fact that a state with nuclear weapons is encouraged to eliminate them unilaterally, with verification of these actions by an international body to be attempted only afterward. Something of this sort occurred with respect to weapons of mass destruction in Iraq, which degenerated into an unprovable morass resulting in catastrophe. Presumably, these issues will be addressed at the first meeting of the treaty’s parties that must convene within a year of its entry into force.

A look to the future

It seems clear that, when the world finally is able to agree to eliminate nuclear weapons, it will not do so directly under the auspices of the Treaty on the Prohibition of Nuclear Weapons. This abolition will take place as a result of an entirely new treaty or set of treaties negotiated by all states with nuclear weapons plus the overwhelming majority of other states. This would probably be accomplished via a careful step-by-step process focused on a steady reduction in numbers and accompanied by resolute tightening of verification and enforcement requirements. Those who negotiated and supported the TPNW may be appreciated as having played an important, catalytic role in this long process.

The legal and political debate about the Treaty on the Prohibition of Nuclear Weapons should be mutually respectful and accurate, while recognizing the divergent merits of the treaty’s pro and con arguments. Disingenuous overstatements and mischaracterizations of the treaty on either side do not help.