Antonyms for compulsory

binding:

inessential, unstipulated, liberated, free, unnecessary, Liberalized, voluntary, optional.

noun:

ductile, contingent, responsible, meek, docile, chosen, unwanted, lowly, inconsequential, submissive, yielding, complaisant, constitutional, compliant, accountable, mild, unnecessary, humble, conditional, limited, dispensable, insignificant, unneeded, gentle, lenient, unimportant, nonessential.

n.:

discretional.

compulsory:

optional, discretionary, voluntary.