religious exemptions to a dress code rule?

i work at a costco in ontario, night shift stocking stuff. until now the rule has been that nobody cares if you wear hats / hoodies as long as you take it off when the store opens and customers come in.

recently, for zero reason at all besides “this is the new dress policy” (even though it is not mentioned in the employee handbook and we haven’t been issued new versions of a new handbook if there is one) one manager has started freaking out about night shift employees wearing hats, despite the fact 99/100 times she only ever comes in during the day shift. if she does come in during the night shift it’s for like one hour at the end. none of the other managers below her give a shit, but she’s serious spazzing out about it.

all the nightshift employees find this to be a load of bullshit, especially considering that the rule is completely arbitrary and no controversy involving a hat happened that inspired them to change the policy.

in any case a few people who oppose this change have decided to just wear turbans instead, because employers aren’t allowed to make you remove religious headwear. my question is this: do we need to be able to somehow prove that we are sikh to our employers? if someone simply arrives wearing a turban are they granted the legal protection?