-MM
The Society of Motion Picture and Television Engineers is investigating the registration of URN:UL for Universal Labels (as defined by ANSI / SMPTE 298M-1997).
While it is clear from RFC 3406 that two-letter NIDs that are Country Codes are reserved, "UL" is not a two-letter ISO 3166-1 Country Code.
So is URN:UL an allowable NID?