Retired in ISO 639-3: Chumash is actually a family name, not a language name. Language family members already have code elements: Barbareño [boi], Cruzeño [crz], Ineseño [inz], Obispeño [obi], Purisimeño [puy], and Ventureño [veo]
Excerpt from change request document:
In the 13th edition of Ethnologue and in older linguistic literature on Native America "Chumash" was listed by itself as a single language. Since the middle of the 20th century, however, it has been recognized that Chumash was a family of six mutually unintelligible languages. In the 14th edition of Ethnologue, the six constituent languages were added, but the entry "Chumash" was not deleted, resulting in the retention of "Chumash" as a constituent of itself. All specialist literature on the languages of California list 6 languages as constituents of the Chumash language family.