(1)  Subject to subsection (2) , in proceedings under this Act for an offence in relation to the sale or supply of a substance or plant, it is no defence that the defendant is only the agent or servant of the owner of, or person dealing in, that substance or plant but the agent or servant and the owner or person dealing in the substance or plant are both liable.

(2)  A servant is not liable if he proves that the offence was committed in a store, shop, stall, or other similar place in which business was, at the time of the commission of the offence, conducted under the personal superintendence of the owner of the business or some manager or other person representing him.