9.3. After-the-Fact Registrations

Occasionally, the IETF becomes aware that an unassigned value from a namespace is in use on the Internet or that an assigned value is being used for a different purpose than it was registered for. The IETF does not condone such misuse; procedures of the type described in this document need to be applied to such cases, and it might not always be possible to formally assign the desired value. In the absence of specifications to the contrary, values may only be reassigned for a different purpose with the consent of the original assignee (when possible) and with due consideration of the impact of such a reassignment. In cases of likely controversy, consultation with the IESG is advised.

This is part of the reason for the advice in Section 3.1 about using placeholder values, such as "TBD1", during document development: problems are often caused by the open use of unregistered values after results from well-meant, early implementations, where the implementations retained the use of developmental code points that never proceeded to a final IANA assignment.