Biosecurity presents several structural problems to states.
First, the Biological Weapons Convention (BWC) does not guarantee states will not develop biological weapons. The BWC guarantees that states say they will not develop biological weapons. Although the BWC offers many benefits, such as reinforcing an international norm against bio-weapons, we should be cautious not to overstate its effect. In explaining the causes of war, Michael Fearon posited the “commitment problem,” which basically states that even if states sincerely promise to follow through on something, they may change their policy later. The Federation of American Scientists argues that the US has even re-interpreted its obligations under the BWC and now accepts development of bio-weapons as long as they are not lethal. For example, North Korea was a signatory to the Nuclear Nonpoliferation Treaty (NPT), but then changed course and build some nuclear weapons. It is always possible other states will do the same with regards to the BWC.
Second and related to the first, bio-weapons programs are often very hidden from the public and other states. Unlike commitments to not move troops near borders, bio-weapons programs cannot be viewed from satellites and leave a smaller footprint than troop movements. Bio-weapons programs present a difficulty similar to nuclear weapons programs however nuclear weapons programs receive much more attention in the international arena.
Third, bio-defense requires more international coordination than other security problems. The interconnectedness of our modern world means that biological attacks somewhere in the world could spread across international lines.
Fourth, biological attacks are very likely to be asymmetrical and unconventional. A small and weak group or state can threaten the strongest states with biological attack.
These are several problems that biological weapons present unlike other security threats. International cooperation is a difficult challenge, but must be pursued vigorously. Agreements are great, but what they actually mean in practice is key.