Stores can't force you to wear a mask, they can't deny you entering the stores but they can be fined however for not displaying a sign that says to wear a mask.

Or so I've read and lost the link...sorry

edit Stores are required to post a sign about the bylaw and are not required or have the right to enforce the bylaw.

https://calgaryherald.com/news/local-news/city-council-looks-at-broader-mask-mandate-for-all-indoor-public-spaces