"It might possibly be an idea to understand the law if a person enters your store with a valid medical exemption for not wearing a mask. Firstly, only an authorised medical officer can ask a person to divulge their medical status. It is against the law to insist that person show anyone in the store their exemption. Penalties apply for doing so. You can ask and nothing more. Secondly to deliberately broadcast to the store that there is a mask less person on the premises causing that person great embarrassment is a vindictive, ignorant action that will, should it happen again attract legal action. Learn the law."