illegal
impermissible
absurd
banned
barred
closed-out
contraband
contrary to reason
criminal
debarred
deported
ejected
excluded
exiled
expelled
forbade
forbid
forbidden
hopeless
illegitimate
illicit
impossible
inconceivable
left out
liquidated
logically impossible
nonpermissible
not in it
not included
not permitted
not possible
off limits
out of bounds
outlawed
oxymoronic
paradoxical
precluded
preposterous
purged
ridiculous
ruled out
ruled-out
self-contradictory
shut out
taboo
tabooed
unallowed
unauthorized
under the ban
exhibited