Since cannabis is a hallucinogen (although some dispute this), the Commentary speculates that mescaline, psilocybin, tetrahydrocannabinol, and LSD could have been considered sufficiently cannabis-like to be regulated under the Single Convention; however, it opines, "It appears that the fact that the potent hallucinogenics whose abuse has spread in recent years have not been brought under international narcotics control does not result from legal reasons, but rather from the view of Governments that a regime different from that offered by the Single Convention would be more adequate." That different regime was instituted by the 1971 Convention on Psychotropic Substances. The Convention on Psychotropic Drugs' scope can include any drug not already under international control if the World Health Organization finds that: