Biological weapons

According to your readings, biological weapons can easily be dispersed through numerous methods to impact livestock, crops, and processed foods, which may effectively randomly infect all humans coming in contact with the contaminated food sources. Regardless of the reason for the use of such weapons, how can a terrorist organization or country at war with another country justify the use of such weapons? Should those organizations or countries be held liable for such actions? If so, what sanctions could be levied against other countries or international organizations?