Biological and chemical warfare overlap to some extent, as the use of toxins produced by certain living organisms is taken into account in both the provisions of the BTWC and the Chemical Weapons Convention. Toxins and psychochemical weapons are often referred to as medium-spectrum agents. Unlike biological weapons, these medium-spectrum agents do not multiply in their host and are usually characterized by shorter incubation times.  The BTWC has no enforcement mechanism against parties seeking to develop, produce or store germ warfare agents. For many years, diplomats in Geneva negotiated to arrive at legally binding mechanisms to enforce the law. The Fifth Review Conference was held in November/December 2001, at a time when concerns about international terrorism following the attacks of 11 December 2001 had been raised. September and the anthrax attacks of 2001. However, the United States Government has decided to withdraw from discussions on strengthening the Convention by adding a legally binding implementation mechanism. This has indeed derailed talks on this issue and stunned negotiators from other countries. Many analysts, including Matthew Meselson, a Harvard University biologist who helped draft a treaty banning biological weapons, and Amy Smithson, a biological and chemical weapons specialist at the Washington-based Stimson Center, criticized the U.S.
decision as undermining international efforts against nonproliferation and as a contradiction to the U.S. government`s rhetoric regarding the alleged threat of biological weapons by Iraq and other enemies of the United States.  The conference was suspended for one year. When the Fifth Review Conference was reconvened in November 2002, it decided to hold annual meetings of the States parties during the transition period leading up to the 2006 Review Conference in order to consider and promote common understanding and effective action on a number of other issues.  The Eighth REVIEW CONFERENCE of the BTWC, held in Geneva in November 2016, had only minimal success, according to Arms Control Today, and adopted an outcome document that reflected the outcome document of the Seventh Review Conference. While Western countries wanted to look for ways to counter rapidly advancing technological changes, most participating countries, including Iran and some Non-Aligned Movement States, saw the results as a missed opportunity to advance measures to strengthen the legally binding agreement banning the development of biological agents. and hoped that the negotiations would continue their efforts to resume the adoption of the BTWC Protocol.  In 2004, the UN Security Council adopted Resolution 1540, which obliges all UN Member States to develop and implement appropriate legal and regulatory measures against the proliferation of chemical, biological, radiological and nuclear weapons and their means of delivery, in particular to prevent the proliferation of weapons of mass destruction to non-state actors.  While these SynBio applications are not inherently illegal or subject to the applicable contractual prohibition, they could be used in some way. In this context, the principles of the right of purpose – distinction, proportionality, military necessity and feasible precautions in the event of an attack – will always determine how weapons are used. The technology can produce weapons that offer even greater differentiation because they can be designed to target specific fighters or groups of fighters based on specific characteristics or prescribed attributes, such as crew or even previous exposure to vaccines. Such weapons would not be illegal per se during armed conflicts.
However, their use would be subject to the rules governing the conduct of hostilities and would be judged on a case-by-case basis. In short, SynBio and its convergence with new technologies can create weapons that are not currently prohibited by universal disarmament commitments or customary international law, and this legal vacuum increases the prospect of arming non-biological threat agents adapted to the targeted effects. These tactical biotechnological capabilities could potentially have strategic consequences and still lie outside the existing regime.