Legal Question in Employment Law in California

There is no law which requires employers to provide bereavement leave. Such leaves are left to the discretion of the employer to decide if they wish to implement such a policy and, if so, how they are to be applied. Since you are a government employee, you would need to turn to your union to see whether bereavement leave is a bargained for benefit and, if so, does it apply to the death of non-relatives.

Bereavement is not sick leave. As Mr. Kirschbaum says, bereavement leave is a separate form of leave that may or may not be offered at all and is offered under various terms when it is offered. If the union contract or other government employment policy applicable to your job and pay grade do not provide for bereavement leave, or does not permit it for non-relatives, then your supervisor is correct that you have to choose between taking it as unpaid leave if that is allowed, or taking it as a charge against vacation time.