Biological and Toxic Weapons Convention (BWC)
The BWC opened for signature on April 10th, 1972, and entered into force on March 26, 1975. It bans the development, stockpiling, and production of biological agents and toxins "of types and in quantities that have no justification for prophylactic, protective, or other peaceful purposes" and weapons, equipment, and delivery vehicles "designed to use such agents or toxins for hostile purposes or in armed conflict." (find source)
"Article I
Each State Party to this Convention undertakes never in any circumstances to develop, produce, stockpile or otherwise acquire or retain:
(1) Microbial or other biological agents, or toxins whatever their origin or method of production, of types and in quantities that have no justification for prophylactic, protective or other peaceful purposes;
(2) Weapons, equipment or means of delivery designed to use such agents or toxins for hostile purposes or in armed conflict."
(Article 1, Biological and Toxic Weapons Convention (BWC)