Black’s Law Dictionary :

MANDATE: Under Roman and Civil Law, a written command given by a principal to an agent, specifically a commission or a contract by which one PERSON requests someone to perform some service gratuitously the commission becoming effective when when the mandatary agrees.

Request: (not an order or law)
Gratuitously: (voluntarily)
Agree: (option to disagree)

If the Mandatary (the public) doesn’t agree the commission is not effective and the mandate is not carried out = made legal

Mandate is NOT law
However law can be agreed upon by acquiescence
If enough mandataries (the public) agree by their acts of gratuity (voluntary act) then it can later become law: hence COMPULSORY

A man-date is just 2 men out to dinner