Biological Weapons Convention

The Biological Weapons Convention (BWC), or Biological and Toxin Weapons Convention (BTWC), is a disarmament treaty that effectively bans biological and toxin weapons by prohibiting their development, production, acquisition, transfer, stockpiling and use. The treaty's full name is the Convention on the Prohibition of the Development, Production and Stockpiling of Bacteriological (Biological) and Toxin Weapons and on their Destruction.

Having entered into force on 26 March 1975, the BWC was the first multilateral disarmament treaty to ban the production of an entire category of weapons of mass destruction. The convention is of unlimited duration. As of May 2025, 189 states have become party to the treaty. Four additional states have signed but not ratified the treaty, and another four states have neither signed nor acceded to the treaty.

The BWC is considered to have established a strong global norm against biological weapons. This norm is reflected in the treaty's preamble, which states that the use of biological weapons would be "repugnant to the conscience of mankind". It is also demonstrated by the fact that not a single state today declares to possess or seek biological weapons, or asserts that their use in war is legitimate. In light of the rapid advances in biotechnology, biodefense expert Daniel Gerstein has described the BWC as "the most important arms control treaty of the twenty-first century". However, the convention's effectiveness has been limited due to insufficient institutional support and the absence of any formal verification regime to monitor compliance. The treaty has seen notable violations in offensive biological weapons programs of the Soviet Union, and of Ba'athist Iraq. Its Article VI mechanism for complaint of a violation has been invoked once, by Russia in 2022, regarding the debunked Ukraine bioweapons conspiracy theory.

While the history of biological warfare goes back more than six centuries to the Siege of Caffa in 1346 CE, international restrictions on biological warfare began only with the 1925 Geneva Protocol, which prohibits the use but not the possession or development of chemical and biological weapons. Upon ratification of the Geneva Protocol, several countries made reservations regarding its applicability and use in retaliation. Due to these reservations, it was in practice a "no-first-use" agreement only. In particular, it did not prevent multiple states from starting and scaling offensive biological weapons programs, including the United States (active from 1943 to 1969) and the Soviet Union (active from the 1920s until at least 1992).

The American biowarfare system was terminated in 1969 by President Nixon when he issued his Statement on Chemical and Biological Defense Policies and Programs. The statement ended, unconditionally, all U.S. offensive biological weapons programs. When Nixon ended the program the budget was $300 million annually.

The BWC sought to supplement the Geneva Protocol and was negotiated in the Conference of the Committee on Disarmament in Geneva from 1969 to 1972, following the conclusion of the negotiation of the Treaty on the Non-Proliferation of Nuclear Weapons. Of significance was a 1968 British proposal to separate consideration of chemical and biological weapons and to first negotiate a convention on biological weapons. The negotiations gained further momentum when the United States decided to unilaterally end its offensive biological weapons program in 1969 and support the British proposal. In March 1971, the Soviet Union and its allies reversed their earlier opposition to the separation of chemical and biological weapons and tabled their own draft convention. The final negotiation stage was reached when the United States and the Soviet Union submitted identical but separate drafts of the BWC text on 5 August 1971. The BWC was opened for signature on 10 April 1972 with ceremonies in London, Moscow, and Washington, D.C., and it entered into force on 26 March 1975 after the ratification by 22 states, including its three depositary governments (the Soviet Union, the United Kingdom, and the United States).

There have been some concerned scientists who have called for the modernization of the BWC at the periodic Review Conferences. For example, Filippa Lentzos and Gregory Koblentz pointed out in 2016 that "crucial contemporary debates about new developments" for the BWC Review Conferences included "gain-of-function experiments, potential pandemic pathogens, CRISPR and other genome editing technologies, gene drives, and synthetic biology".

With only 15 articles, the BWC is relatively short. Over time, the treaty has been interpreted and supplemented by additional politically binding agreements and understandings reached by its States Parties at eight subsequent Review Conferences.