It's all about the following, I know some producers and vendors are not going to sell after May 26th
Meaning of “psychoactive substance” etc
(1)In this Act “psychoactive substance” means any substance which—
(a)is capable of producing a psychoactive effect in a person who consumes it, and
(b)is not an exempted substance (see section 3).
(2)For the purposes of this Act a substance produces a psychoactive effect in a person if, by stimulating or depressing the person’s central nervous system, it affects the person’s mental functioning or emotional state; and references to a substance’s psychoactive effects are to be read accordingly.
(3)For the purposes of this Act a person consumes a substance if the person causes or allows the substance, or fumes given off by the substance, to enter the person’s body in any way.
I did get the following response from one vendor "CBD is not psychoactive and is a food supplement so we believe it will not come under the act"