Thanks for the comment. Indeed, you're right; the Psychoactive Substances Act of 2016 doesn't mention possession of psychoactive substances per verbatim. However, the act prohibits psychoactive substances and creates a list of substances that are allowed to be psychoactive substances. And Kratom is not on the list of these substances... (That's the Psychoactive Substances Act 2016, c 3) Kratom, being a psychoactive substance, is de jure prohibited. Where the consumption or possession is not