General Purpose Criterion

The general-purpose criterion Is an important concept in international law which broadly governs international agreements with respect to chemical weapons (CW). Although the term is not found within such agreements, it is "regularly used" to describe the comprehensive nature of prohibitions regarding all CW.

The scope of this criterion broadly governs the purpose of chemical agents opposed to specific objects. Therefore the prohibitions are not limited to a specific list, but encompass all CW to include future incarnations.

...
Wikipedia