Adjective for "must not be present"

Is there an adjective that describes something that must be omitted/absent in a particular context?

For example, consider this software documentation that explains the relationship between two different variables:

• When contentType = 'application/json', schemaVersion is required (must be present).
• When contentType = 'x-vendor/manifest', schemaVersion is optional (may be present or absent).
• When contentType = 'image/jpeg', schemaVersion is _______ (must be absent).

What word can be used to fill in the blank?

Prohibited.
See the W3school definition of the use attribute in XML which is for exactly this characteristic :

use

[...] Specifies how the attribute is used.
Can be one of the following values:

optional - the attribute is optional (this is default).
prohibited - the attribute cannot be used.
required - the attribute is required.

Forbidden

forbidden, adj

1 : not permitted or allowed

source: Merriam-Webster online

If you don’t insist on a single word, not allowed works. There’s also disallowed.

Note also some useful in-between words:

• … schemaVersion is recommended (optional, but generally encouraged).
• … schemaVersion is deprecated (optional, but generally discouraged).