Retired in ISO 639-3: Duplicate of Yug [yug]
Excerpt from change request document:
I suggest retiring code [yuu] because [yug] is easier to remember, but if [yuu] is older it might be better to retain it instead. The fact that Ethnologue has an entry for [yuu] but not for [yug] might be reason to retain [yuu], though perhaps they could move their article to [yug].
In order to complete the change request, the form “Request for New Language Code Element in ISO 639-3” (file name “ISO639-3_NewCodeRequestForm.doc” or “ISO639- 3_NewCodeRequestForm.rtf”) must also be submitted for each new identifier that is to be created. That step can be deferred until this form has been processed by the ISO 639-3 registrar, provided that sufficient information on the rationale is given in (b) above.
In the case of a minority language that has been considered in some contexts to be a dialect of a major language, yet is divergent enough to be unintelligible to speakers of the standard variety of the major language, it may be more beneficial for the users of the ISO 639-3 and 639-2 code sets to create a new code element for the divergent language variety without splitting the existing code element of the major language. The ISO 639-3 Registration Authority may make this determination when considering a request involving a major language and a highly distinct “dialect.” If such a course is followed, the rationale for the decision will be published in a comment by the Registration Authority on approval of the requested addition for the divergent variety.