Retailers are permitted to ask if a customer is exempt from the by-law but are not permitted to require proof that an exemption applies. If a customer refuses to wear a mask but does not claim an exemption, retailers should de- escalate the situation and complete the transaction, if necessary, in the interest of staff safety.
The CICC has published an updated list of mandatory mask requirements by region. Check here for updates. Or, consult your local public health authority for further information.