Draft and pass a law that forbids the use of government resources to negatively affect (deliberately) the health of U.S. citizens or residents.
This includes the use (or misuse) of chemical agents that have a negative impact on human health, particularly chemicals like pesticides that can double as biological weapons.
This also includes the use of biological pathogens that may or may not be considered lethal, and may already exist among the population. While it is possible for these pathogens to disseminate naturally among the population, use of government resources to accelerate or deliberately allow the infection new populations should be specifically prohibited as current laws may not expressly forbid these sorts of use of government resources.