The Treaty on the Prohibition of Nuclear Weapons (TPNW), or the Nuclear Weapon Ban Treaty, is the first legally binding international agreement to comprehensively prohibit nuclear weapons, with the goal of leading towards their total elimination. It was passed on 7 July 2017.   In order to come into effect, signature and ratification by at least 50 countries is required. For those nations that are party to it, the treaty prohibits the development, testing, production, stockpiling, stationing, transfer, use and threat of use of nuclear weapons, as well as assistance and encouragement to the prohibited activities. For nuclear armed states joining the treaty, it provides for a time-bound framework for negotiations leading to the verified and irreversible elimination of its nuclear weapons programme.
According to a mandate adopted by the United Nations General Assembly in December 2016,  negotiations on the treaty began in the United Nations in March 2017 and continued from 15 June to 7 July 2017. In the vote on the treaty text, 122 were in favour, 1 voted against (Netherlands), and 1 abstained (Singapore). 69 nations did not vote, among them all of the nuclear weapon states and all NATO members except the Netherlands.
The nuclear-weapon-ban treaty, according to its proponents, will constitute an "unambiguous political commitment" to achieve and maintain a nuclear-weapon-free world.
Proponents of the ban treaty believe that it will help "stigmatize" nuclear weapons, and serve as a "catalyst" for elimination.
Nuclear weapons – unlike chemical weapons, biological weapons, anti-personnel landmines and cluster munitions – are not prohibited in a comprehensive and universal manner.  The Non-Proliferation Treaty (NPT) of 1968 contains only partial prohibitions, and nuclear-weapon-free zone treaties prohibit nuclear weapons only within certain geographical regions.
Overview of provisions
The preamble of the treaty  explains the motivation by the "catastrophic consequences" of a use of nuclear weapons, by the risk of their sheer existence, by the suffering of the hibakusha (the surviving victims of the 1945 atomic bombings of Hiroshima and Nagasaki) and the victims of nuclear tests, by "the slow pace of nuclear disarmament" and by "the continued reliance on nuclear weapons in military and security concepts" like deterrence. It recognizes "the disproportionate impact of nuclear-weapon activities on indigenous peoples". It expresses compliance with existing law: the UN charter, international humanitarian law, international human rights law, the very first UN resolution adopted on 24 January 1946, the NPT, the Comprehensive Nuclear-Test-Ban Treaty and its verification regime, as well as nuclear-weapon-free zones. Furthermore, the "inalienable right" of a peaceful use of nuclear energy is emphasized. Finally, social factors for peace and disarmament are recognized: participation of both women and men, education, public conscience, "international and regional organizations, non-governmental organizations, religious leaders, parliamentarians, academics and the hibakusha".
Article 1 contains prohibitions against the development, testing, production, stockpiling, stationing, transfer, use and threat of use of nuclear weapons, as well as against assistance and encouragement to the prohibited activities. Finally, any direct or indirect "control over nuclear weapons or other nuclear explosive devices" is forbidden.
Article 2 requires each party to declare whether it had nuclear weapons of their own or deployed on its territory, including the elimination or conversion of related facilities.
Article 3 requires parties that do not possess nuclear weapons to maintain their existing IAEA safeguards and, if they have not already done so, to accept safeguards based on the model for non-nuclear-weapon states under the NPT.
Article 4 sets out general procedures for negotiations with an individual nuclear armed state becoming party to the treaty, including time limits and responsibilities.
Article 5 is about national implementation.
According to Articles 13–15, the treaty was open for signature from 20 September 2017 at the UN headquarters in New York.
History, intentions and impact
Proposals for a nuclear-weapon-ban treaty first emerged following a review conference of the NPT in 2010, at which the five officially recognized nuclear-armed state parties – the United States, Russia, Britain, France and China – rejected calls for the start of negotiations on a comprehensive Nuclear weapons convention. Disarmament advocates first considered starting this process without the opposed states as a "path forward".  Subsequently, a less technical treaty concentrated on the ban of nuclear weapons appeared to be a more realistic goal. 
Three major intergovernmental conferences in 2013 and 2014 on the "humanitarian impact of nuclear weapons", in Norway, Mexico and Austria, strengthened the international resolve to outlaw nuclear weapons.
In 2014, a group of non-nuclear-armed nations known as the New Agenda Coalition (NAC) presented the idea of a nuclear-weapon-ban treaty to NPT states parties as a possible "effective measure" to implement Article VI of the NPT, which requires all states parties to pursue negotiations in good faith for nuclear disarmament. The NAC argued that a ban treaty would operate "alongside" and "in support of" the NPT. 
In 2015, the UN General Assembly established a working group with a mandate to address "concrete effective legal measures, legal provisions and norms" for attaining and maintaining a nuclear-weapon-free world.  In August 2016, it adopted a report recommending negotiations in 2017 on a "legally binding instrument to prohibit nuclear weapons, leading towards their total elimination". 
In October 2016, the First Committee of the UN General Assembly acted upon this recommendation by adopting a resolution that establishes a mandate for nuclear-weapon-ban treaty negotiations in 2017 (with 123 states voting in favour and 38 against, and 16 abstaining).  North Korea was the only country possessing nuclear weapons that voted for this resolution, though it did not take part in negotiations.  
A second, confirmatory vote then took place in a plenary session of the General Assembly in December 2016.
From 27 to 31 March 2017, convened as the United Nations Conference to Negotiate a Legally Binding Instrument to Prohibit Nuclear Weapons, Leading Towards their Total Elimination, a first round of negotiations was held at UN headquarters in New York, with the participation of 132 nations.
Summarizing the discussions, a first ban treaty draft  was presented on 22 May by Elayne Whyte Gómez.
Article 1, 1c (in extension of Article 1, 2a) prohibits direct or indirect control of nuclear weapons.
A second conference started at 15 June and was scheduled to conclude on 7 July 2017. 121 out of 193 UN members participated in the negotiations.
During the discussions about Article 1, several states pleaded for an explicit prohibition of nuclear military planning, others of financial assistance to development and production of nuclear weapons.
On 27 June, a second draft was published.
A third draft was presented on 3 July 2017.
The vote on the final draft  took place on 7 July 2017, with 122 countries in favour, 1 opposed (Netherlands), and 1 abstention (Singapore).
Among the countries voting for the treaty's adoption were South Africa and Kazakhstan,  both of which formerly possessed nuclear weapons and gave them up voluntarily. Iran and Saudi Arabia also voted in favour of the agreement. There are indications that Saudi Arabia has financially contributed to Pakistan's atomic bomb projects and in return has the option to buy a small nuclear arsenal,  an option that would be realized in the event that Iran obtains nuclear warheads. 
According to the International Campaign to Abolish Nuclear Weapons (ICAN), a coalition of non-governmental organizations, leading proponents of a nuclear-weapon-ban treaty include Ireland, Austria, Brazil, Indonesia, Mexico, Nigeria, South Africa and Thailand.  All 54 nations of Africa (all but one of which have either signed or ratified the 1996 Treaty of Pelindaba establishing a nuclear-weapon-free-zone in the continent)  and all 33 nations of Latin America and the Caribbean (already in a nuclear-weapon-free-zone under the 1967 Treaty of Tlatelolco)  had subscribed to common regional positions supporting a ban treaty. The 10 nations of the Association of Southeast Asian Nations (ASEAN), which concluded the Southeast Asian Nuclear-Weapon-Free Zone Treaty, participated in the negotiations, but Singapore abstained from the vote. Many Pacific island nations are also supportive. 
No nuclear-armed nation has expressed support for a ban treaty; indeed, a number of them, including the United States,  and Russia,  has expressed explicit opposition. North Korea was the only nuclear state to vote for initiating ban negotiations.  
Many of the non-nuclear-armed members of the North Atlantic Treaty Organization (NATO), along with Australia  and Japan,  are also resistant to a ban treaty, as they believe that US nuclear weapons enhance their security.  A statement was put forward by several NATO members (not including France, the United States, nor the United Kingdom, the nuclear weapon states within NATO), claiming that the treaty will be 'ineffective in eliminating nuclear weapons' and instead calling for advanced implementation of Article VI of the Non-Proliferation Treaty. 
Following the treaty's adoption, the permanent missions of the United States, the United Kingdom and France issued a joint statement indicating that they did not intend "to sign, ratify or ever become party to it".
Contrary to government position in a number of nations, several recent opinion polls – including Australia,  and Norway  – have shown strong public support for negotiating an international ban on nuclear weapons. The Netherlands voted against adoption of the treaty, while Germany did not participate, despite opinion polls against presence of nuclear weapons in both countries.  An example of consensus between government and majority opinion is Sweden. 
The ICAN has been the main civil society actor working alongside governments to achieve a strong and effective ban treaty.
In a July 2017 public statement endorsed by over 40 Buddhist, Christian, Jewish and Muslim leaders and groups, "Faith Communities Concerned about Nuclear Weapons" called for universal adoption of the treaty.
Xanthe Hall (IPPNW and ICAN) said she regretted the boycott of the treaty by all nuclear powers and their allies, but hints at history: also the Mine Ban Treaty or the Convention on Cluster Munitions have been concluded against the states possessing such weapons, but finally were signed by most states. The request of a nuclear ban could only weaken the Non-Proliferation Treaty (NPT), regarding that the nuclear forces were blocking multi-lateral disarmament negotiations since 1995, instead were planning modernization and rearmament. Therefore, they would abdicate from their responsibility of disarmament according to the NPT, Article VI. Then the danger would grow that in reaction other nations felt less stronger bound to non-proliferation. By contrast, the nuclear weapon ban treaty would aim at a new disarmament dynamics, hence would much more recover than weaken the NPT. 
In NATO Review , Rühle indicated that according to proponents, it was intended to strengthen Article VI of the Non-Proliferation Treaty (NPT), which requires good faith efforts to negotiate effective measures on nuclear disarmament. Sceptics have argued that the Ban Treaty would harm the NPT. 
Political parties supporting the government in NATO member states often share the rejection of the nuclear ban negotiations and treaty by their governments.
In response to an appeal made by ICAN, over eight hundred parliamentarians around the world pledged their support for a ban treaty, calling upon "all national governments to negotiate a treaty banning nuclear weapons and leading to their complete eradication" and describing it as "necessary, feasible and increasingly urgent".
As of September 2018, 69 states have signed the Treaty and 19 have ratified it.