They’re not obligatory if you’re permitted to reject them.
"Mandates are optional" sounds like an oxymoron to me.
In your favour though, businesses could have a dress code which is essentially a mandate, and I'd agree it should be their option whether to have a dress code.
But what if the employer decided they are implementing a new dress code where you have to dress as the opposite gender, and the employer couldn't provide any good reason for it? Can they do this if it's not in your employment contract?
Businesses must operate in accordance to the law.
There are "wrongful dismissal" and "unfair dismissal" laws. If I signed a contract with my employer, and nowhere in that contract does it say I'll be required to take all these injections of genetic material which haven't been shown to stop the spread, and I can prove I'm not a Covid threat to them via negative testing and their vaccines giving them protection, this could be the basis for a wrongful/unfair dismissal case.
This document states: "All vaccines must be administered in accordance with the relevant legislation, best practice, and the guidelines and recommendations in this Handbook". The handbook states valid consent is required before administering vaccines, where one of the criteria is that it
"must be given voluntarily in the absence of undue pressure, coercion or manipulation". So clinics shouldn't really be upholding the mandates. When the patient has to give consent, they should mention their employer is pressuring them to have it and the nurse should then not administer the vaccine. The patient would then have a slam dunk wrongful dismissal case as they followed all their employers instructions. It would be like firing a courier driver for not delivering a package to an inaccessible location.
Nobody has been out in prison for refusing to take the vaccine.
People were arrested for protesting the mandates in Canada and Australia, and anyone who shows up to work after being fired for not being vaccinated would be arrested and jailed for trespassing. That also happened to a teacher who didn't use transgender pronouns.