Adjective or locution showing that the absence of something is required?

A general term, a past participle of a phasal verb, is "ruled out".

• These components are ruled out.

Another possibility is the participial adjective "excluded".

• These components are excluded.

Since the context is formally logical, it is strictly necessary to differentiate between 'Must be absent in the syntactic context', or 'Must be absent in this instance'.

To define the absolute case benefits from strict words like forbidden and invalid.

Therefore to denote a local context requires a word with a more relational quality, such as Contraindicated, Conflicting, or Unsuitable.

You might also consider proscribed

Defined by Longman

to officially say that something is not allowed to exist or be done

Synonyms: forbid, prohibit, disallow