The Chemical Weapons Convention (CWC), officially the Convention on the Prohibition of the Development, Production, Stockpiling and Use of Chemical Weapons and on their Destruction, is an arms control treaty administered by the Organisation for the Prohibition of Chemical Weapons (OPCW), an intergovernmental organization based in The Hague, Netherlands. The treaty entered into force on 29 April 1997. It prohibits the use of chemical weapons, and the large-scale development, production, stockpiling, or transfer of chemical weapons or their precursors, except for very limited purposes (research, medical, pharmaceutical or protective). The main obligation of member states under the convention is to effect this prohibition, as well as the destruction of all current chemical weapons. All destruction activities must take place under OPCW verification.
As of August 2022, 193 states have become parties to the CWC and accept its obligations. Israel has signed but not ratified the agreement, while three other UN member states (Egypt, North Korea and South Sudan) have neither signed nor acceded to the treaty. Most recently, the State of Palestine deposited its instrument of accession to the CWC on 17 May 2018. In September 2013, Syria acceded to the convention as part of an agreement for the destruction of Syria's chemical weapons.
Under the convention, the entirety of the chemical weapons stockpiles declared by the States Parties to the convention have been irreversibly destroyed, an achievement reached in July 2023. The convention has provisions for systematic evaluation of chemical production facilities, as well as for investigations of allegations of use and production of chemical weapons based on the intelligence of other state parties.
Some chemicals which have been used extensively in warfare but have numerous large-scale industrial uses (such as phosgene) are highly regulated; however, certain notable exceptions exist. Chlorine gas is highly toxic, but being a pure element and widely used for peaceful purposes, is not officially listed as a chemical weapon. Certain state powers (e.g. the former Assad regime of Syria) continued to regularly manufacture and implement such chemicals in combat munitions. Although these chemicals are not specifically listed as controlled by the CWC, the use of any toxic chemical as a weapon (when used to produce fatalities solely or mainly through its toxic action) is in and of itself forbidden by the treaty. Other chemicals, such as white phosphorus, are highly toxic but are legal under the CWC when they are used by military forces for reasons other than their toxicity.
The CWC augments the Geneva Protocol of 1925, which bans the use of chemical and biological weapons in international armed conflicts, but not their development or possession. The CWC also includes extensive verification measures such as on-site inspections, in stark contrast to the 1975 Biological Weapons Convention (BWC), which lacks a verification regime.
After several changes of name and composition, the ENDC evolved into the Conference on Disarmament (CD) in 1984. On 3 September 1992 the CD submitted to the U.N. General Assembly its annual report, which contained the text of the Chemical Weapons Convention. The General Assembly approved the convention on 30 November 1992, and the U.N. Secretary-General then opened the convention for signature in Paris on 13 January 1993. The CWC remained open for signature until its entry into force on 29 April 1997, 180 days after the deposit at the UN by Hungary of the 65th instrument of ratification.
Organisation for the Prohibition of Chemical Weapons (OPCW)
The convention is administered by the Organisation for the Prohibition of Chemical Weapons (OPCW), which acts as the legal platform for specification of the CWC provisions. The Conference of the States Parties is mandated to change the CWC and pass regulations on the implementation of CWC requirements. The Technical Secretariat of the organization conducts inspections to ensure compliance of member states. These inspections target destruction facilities (where constant monitoring takes place during destruction), chemical weapons production facilities which have been dismantled or converted for civil use, as well as inspections of the chemical industry. The Secretariat may furthermore conduct "investigations of alleged use" of chemical weapons and give assistance after use of chemical weapons.
The 2013 Nobel Peace Prize was awarded to the organization because it had, with the Chemical Weapons Convention, "defined the use of chemical weapons as a taboo under international law" according to Thorbjørn Jagland, Chairman of the Norwegian Nobel Committee.
Prohibition of production and use of chemical weapons
Destruction (or monitored conversion to other functions) of chemical weapons production facilities
Destruction of all chemical weapons (including chemical weapons abandoned outside the state parties territory)
Assistance between State Parties and the OPCW in the case of use of chemical weapons
An OPCW inspection regime for the production of chemicals which might be converted to chemical weapons
International cooperation in the peaceful use of chemistry in relevant areas
The convention distinguishes three classes of controlled substance, chemicals that can either be used as weapons themselves or used in the manufacture of weapons. The classification is based on the quantities of the substance produced commercially for legitimate purposes. Each class is split into Part A, which are chemicals that can be used directly as weapons, and Part B, which are chemicals useful in the manufacture of chemical weapons. Separate from the precursors, the convention defines toxic chemicals as "[a]ny chemical which through its chemical action on life processes can cause death, temporary incapacitation or permanent harm to humans or animals. This includes all such chemicals, regardless of their origin or of their method of production, and regardless of whether they are produced in facilities, in munitions or elsewhere."
Schedule 1 chemicals have few, or no uses outside chemical weapons. These may be produced or used for research, medical, pharmaceutical or chemical weapon defence testing purposes but production at sites producing more than 100 grams per year must be declared to the OPCW. A country is limited to possessing a maximum of 1 tonne of these materials. Examples are sulfur mustard and nerve agents, and substances which are solely used as precursor chemicals in their manufacture. A few of these chemicals have very small scale non-military applications, for example, milligram quantities of nitrogen mustard are used to treat certain cancers.
Schedule 2 chemicals have legitimate small-scale applications. Manufacture must be declared and there are restrictions on export to countries that are not CWC signatories. An example is thiodiglycol which can be used in the manufacture of mustard agents, but is also used as a solvent in inks.