Dear Peter,
As you seem to have doubts about the fact that "administrative use" defined in ISO 3166-1:2006 (or quasi-equivalently the list of languages defined in Part 3 of the "Technical reference Manual for the standardization of Geographical Names" edited in 2007 as document M87 of the UNGEGN) could have external use, I join to the present message an ICANN report (Final report IDN ccNSO Policy Development Process) dated 29 May 2013 by Bart Boswinkel.
Notably, see point "Distinguished Languages" as defined in point "D: A meaningful representation of the name of a territory must be in a Distinguished Language of the Territory" of the "2.1.2: Criteria for the selection  of an IDN ccTLD string" within "2.1: Policy Recommendations IDN ccTLD Strings Selection Criteria, Requirements and Process" of "2: Recommendations", pages 8-9.
Let me add that Bart is the substitute of Jaap Akkerhuis as ICANN's  representative in the ISO 3166 Maintenance Agency.
Bien cordialement.
Gérard Lang