Despite the heated debate over the impact on disarmament of the Treaty on the Prohibition of Nuclear Weapons (TPNW), informally known as the ban treaty, there has been sparse research to support asserted speculations. Analysis of past prohibitions on biological and chemical weapons, landmines, and cluster munitions could help to fill this void. While no other weapon prohibition is a perfect fit, using analogous data on previous bans to provide insight on possible futures could be more productive than making unsubstantiated projections. If the nuclear ban treaty does follow the historical trajectories of the two models studied below, it could strengthen the norm against nuclear weapons use and possession and even decrease production of nuclear weapons. However, these models show that strengthening norms is not the conclusive step toward a weapons-free world, and additional, difficult work likely lies ahead. The Models 1925 Geneva Protocol The Protocol for the Prohibition of the Use in War of Asphyxiating, Poisonous or Other Gases, and of Bacteriological Methods of Warfare, also known as the 1925 Geneva Protocol, closely fits the intent of the nuclear prohibition treaty. The protocol was conceived as an interim measure to precede comprehensive elimination conventions. It didn’t by itself eliminate any weapons; like the TPNW, the Geneva Protocol sought instead to shape the norm around the banned weapon. However, the Geneva Protocol is much more limited in scope than the TPNW: it only banned the weapons’ use and had far fewer negotiators and signatories than the TPNW. Several decades after the Geneva Protocol, two comprehensive elimination treaties on biological and chemical weapons were adopted. The Biological Weapons Convention (BWC) entered into force in 1975 and the Chemical Weapons Convention (CWC) in 1993. Both follow-on treaties had the support of major weapons possessors, unlike the Geneva Protocol. Landmine Ban Treaty and Cluster Munitions Convention The structure and negotiating process of the nuclear ban closely fits the 1997 Convention on the Prohibition of the Use, Stockpiling, Production and Transfer of Anti-Personnel Mines and On Their Destruction, or Mine Ban Treaty, and the 2008 Cluster Munitions Convention. All three “humanitarian disarmament” treaties were negotiated outside the Conference on Disarmament and in a series of conferences – the Ottawa Process in the case of the Landmine Ban Treaty and the Oslo Process in the case of the Cluster Munitions Convention. Neither treaty had support of all major weapon possessors. Instead, a core group of nations and civil society organizations pushed for their adoption and stayed involved afterwards, publishing annual reports on treaty implementation and impact. Yet, while the landmine and cluster munitions bans were intended to be definitive elimination treaties, the TPNW was intended as a first step toward a comprehensive nuclear elimination convention. Prohibition Impact The Geneva Protocol, as previously mentioned, did not result in the destruction of biological and chemical weapons. Its follow-on conventions, the Biological Weapons Convention and Chemical Weapons Convention, have led countries to destroy the banned weapons and reduce their use, but there been exceptions. Both the mine ban and the Cluster Munitions Convention led to increased destruction of the prohibited weapon by states-parties and decreased production by non-states-parties. Most countries do not use either weapon, although some use persists in a handful of outlier states. As a caveat, both of these treaties were adopted relatively recently, so only the short-term implications can be assessed. Destruction To date, 96 percent of all declared chemical weapons stockpiles have been destroyed. The landmine ban’s 164 states-parties (including Palestine) have destroyed more than 53 million landmines, but another 50 million landmines may remain stockpiled by non-states-parties. As for cluster munitions, 98 percent of states-parties’ cluster submunitions, and 97 percent of states-parties’ cluster munitions stockpiles, have been destroyed. Yet, 47 cluster-bomb-possessing-states have not signed the ban. Production Forty-one out of the more than 50 countries that at one time produced landmines and eighteen of the 34 states that once produced cluster munitions have stopped production. The impact on production is not limited to states-parties. Textron, the last U.S. company still producing cluster munitions, announced that it would stop producing its sensor-fuzed weapon in 2016, even though the United States is not party to the treaty. Argentina, another non-signatory, also stopped producing cluster munitions. Use Biological weapons were used in lab experiments in World War II, but since the 1925 Geneva Protocol, they have not been used in combat. Casualties from chemical weapons use have declined since the CWC’s adoption. However, it has been unsuccessful in preventing them altogether. Chemical weapons have been used in World War II, the Vietnam War, the Iraq-Iran war, and most recently in the Syrian civil war. Use of anti-personnel factory-made mines by states has decreased since prohibition, although there has been a rise in the use of improvised mines by non-state actors in recent years. Myanmar and North Korea were the only states to use landmines in the past year. Likewise, cluster bomb use was only reported in two countries in 2017, neither of which have signed the ban: Yemen and Syria. A total of 21 states have used cluster bombs in the past, including France, Russia, and the United States. The landmine ban also impacted use policies for non-states-parties — the United States outlawed the use of landmines everywhere except for the Korean peninsula in 2014. Looking forward Do weapons prohibitions work? When looking at the impact of past weapons prohibitions, it seems clear that the very existence of the prohibition did not impede disarmament, as the United States, among others, has claimed the TPNW will do. Clearly, bans that include weapons possessors, like the Biological Weapons Convention, Chemical Weapons Convention, Landmine Ban Treaty and Convention on Cluster Munitions, led those weapons possessors to destroy their arsenals because they were obligated to do so under the treaty. Even a ban that did not include any weapons possessors, the 1925 Geneva Protocol, set the stage for prohibition treaties that did cause actual weapon elimination. While it is difficult to prove a causal link between prohibition and bolstering the norm against non-use and non-possession, some argue that the change in weapons policies of non-states-parties that closely followed the adoption of a ban on the weapon, such as the change in U.S. policy on landmines, is an indication of the normative impact of the prohibition. Although the United States has publicly stated that the nuclear prohibition treaty will have no impact on it or other non-signatories, it has privately indicated otherwise. A leaked October 2016 U.S. government memo to NATO allies expresses concern about the “wide-ranging” effects of a nuclear prohibition on its “security relationships,” despite the fact that neither the United States or a single NATO member signed, or even participated in the negotiation of, the ban treaty. It is fair to say that ban treaties have not harmed disarmament, and they have arguably had a record of success in pushing it forward by strengthening the norm against that weapon, even for those who have not joined the treaty. However, the more important question for those concerned about the threat that the use of these weapons pose, is really not whether prohibitions have worked, but instead how the international community can take forward disarmament after a weapon has been banned, a question that has become increasingly prominent in the light of recent chemical weapons use in Syria. Just as the international community continues to pursue new initiatives to counter the use of chemical weapons in Syria even after the chemical weapons ban, including through a new French project, the International Partnership Against the Impunity For the Use of Chemical Weapons, those who support nuclear disarmament must continue to seek out additional efforts to bolster the nuclear disarmament regime after the nuclear ban. That’s why states opposing and supporting the ban treaty must work together to continue to strengthen the norm against nuclear weapons use and possession, including by: Supporting restarting U.S./Russian arms control dialogues; Advocating for the entry into force of the Comprehensive Test Ban Treaty; Negotiating a Fissile Material Cutoff Treaty; Engaging constructively in the 2020 Nuclear Nonproliferation Treaty (NPT) Review Conference cycle; Pursuing innovative projects, like the International Partnership for Nuclear Disarmament Verification. Progress on these steps, which are loosely based on proposals agreed to by all states in the 2000 NPT Review Conference final document, has been admittedly slow or stagnant in recent years. And yet, abandoning them would undermine existing legal (under Article VI of the NPT) and moral (according to Pope Francis, at least) disarmament obligations. In brief, historical models indicate the TPNW does not threaten disarmament, but that it’s also not the final step to a nuclear-free-world. Just as the international community has pushed for additional measures to prevent the use and stockpiling of other banned weapons, so too must all those who are working toward a nuclear-free-world continue to actively pursue old and new steps to get there. *Views represented here are those of the author and do not necessarily represent those of the Arms Control Association.