impermissible
banned
barred
contraband
forbade
forbid
illegal
illicit
interdicted
nonpermissible
not permitted
off limits
out of bounds
outlawed
prescribed
prohibited
ruled out
taboo
tabooed
unallowed
unauthorized
under the ban
unlawful
unlicensed
unpermissible
unsanctioned
untouchable
verboten
vetoed
glidden
hidden
overridden
ridden