Unlawful, unapproved, illicit.

That may or should be disallowed (in various senses of disallow, v.); that is not to be allowed, permitted, or approved; impermissible.

Not allowable; inadmissible, impermissible.

Scottish. Not freed or let go.

Not permitted; forbidden.

Not authorized or allowed; improper, irregular; esp. not sanctioned by law, rule, or custom; unlawful, forbidden.

(un-, prefix1 affix 2a affix 2c.)

figurative. Forbidden, illegitimate, unauthorized.

= illicit, adj.

Not admissible; inadmissible.

Not permissible; unallowable, disallowed. Cf. impermissible, adj.

Not admissible; not to be admitted, entertained, or allowed.

That cannot or should not be permitted; unallowable.