Mark a taxonomy term as "deprecated" I have a taxonomy vocabulary "categories", and decide that one of the terms should no longer be used (because I introduced another field which covers this information).

I could delete the term, but then some existing content would no longer have a category.

What I would like is to "deprecate" the term, such that


existing content can continue to reference the term.
the term is still visible in things like search facets.
the term can no longer be assigned in a term reference field.
(optional) editing an existing node which references the old term will fail form validation on save, and force to change the term.
Termsatus module can help you.

This add a status "publis" or "unpublish" on terms like nodes, and is handled by permission (that can solve first three points), views, etc.

I think the optional point need a custom code using hook_node_validate check the status of term an send the custom error message attached to the field.