The Biological and Toxin Weapons Convention (BTWC) bans the acquisition, possession and transfer of biological weapons. The core prohibitions of the BTWC reside in Articles I, II and III. 

The basic prohibition concerns the development, production, stockpiling, other acquisition or retention of microbial or other biological agents or toxins that are harmful to humans, animals or plants, of types and in quantities that have no justification for prophylactic, protective or other peaceful purposes. It also prohibits the weapons, equipment or means of delivery designed to use such agents or toxins in armed conflict or for other hostile purposes. It is the common understanding of all States Parties to the BTWC that the Convention also prohibits any use of biological weapons.

In addition, the transfer to any recipient whatsoever, directly or indirectly, of any of the agents, toxins, weapons, equipment or means of delivery specified in Article I of the BTWC is prohibited. It is the understanding of all States Parties that ‘any recipient whatsoever’ covers any State or non-State actor at the international, national and sub-national levels.

Finally, it is prohibited to in any way to assist, encourage, or induce any State, group of States or international organisations to manufacture or otherwise acquire any of the agents, toxins, weapons, equipment or means of delivery specified in Article I of the BTWC.

These prohibitions apply to the States party to the Convention. Through their constitutional and legislative means, these prohibitions are also applied to natural and legal persons within the jurisdiction of the States Parties. Primary legislation is required in some constitutional systems to translate these provisions into domestic law. This can be done either in a single dedicated Act, or by incorporating these requirements into either existing legislation, or by enacting broadly-framed legislation that might also deal with biosafety, for example. The route is for each State Party to choose. In some (monist) legal systems mere ratification of a treaty translates its contents into domestic law. However, often there are no accompanying penal provisions, which means that even in such a legal system some additional legislation will be needed.

Implementing and penal legislation should include the following core elements:

• Prohibitions criminalising the development, production, stockpiling, acquisition, retention and transfer of microbial or other biological agents, or toxins whatever their origin or method of production, of types and in quantities that have no justification or prophylactic, protective or other peaceful purposes; and weapons, equipment or means of delivery designed to use such agents or toxins for hostile purposes or in armed conflict.
• Extraterritorial application of these prohibitions if undertaken outside the territory of the State Party, but only if breaches are committed by subjects of the State Party.
• Specifying penalties on conviction for contraventions of the core prohibitions.
  
• Provision for offences by legal persons as well as individuals.
• Corresponding changes, if applicable, in military law to reflect the introduction of these prohibitions and to govern the conduct of the armed forces.
  
•  If not already provided for elsewhere, provisions to enforce these laws, including powers of search and for obtaining evidence in cases of suspected breaches of the legislation.
  
• Prohibition of assisting others, whether within the territory of the State Party or overseas, to breach any of the Convention’s prohibitions.