impermissible

Something impermissible isn't allowed. It's impermissible in every part of the U.S. to drive 100 miles an hour on the highway.

Things that are permissible are legal, authorized, or welcome — you are permitted to do them. The opposite of permissible is impermissible, which adds the "opposite" prefix im- to permissible, from the Latin permittere, "let, allow, grant, or permit." It's impermissible to bully other kids at school, or against the rules, and it's impermissible to steal a car, or against the law.

Definitions of impermissible
1

adj not permitted

impermissible behavior”
Synonyms:
forbidden, out, prohibited, proscribed, taboo, tabu, verboten
excluded from use or mention
unmentionable
unsuitable or forbidden as a topic of conversation
untouchable
forbidden to the touch
intolerable, unbearable, unendurable
incapable of being put up with
Antonyms:
allowable, permissible
that may be permitted especially as according to rule
tolerable
capable of being borne or endured
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adj not allowable

Synonyms:
inadmissible
not deserving to be admitted