Also there should exist somewhere a registry of known flag codes. There are wellknown vexillologic sites that list large collections of flags, but for now they still did not develop a standard (ASCII-based) codification.
In my opinion, this codication should just need BASIC LATIN CAPITAL LETTERs, Arabo-European digits, the ASCII HYPHEN as a separator for country/region subcodes, and the colon and dot for versioning/dating, and it should be based on ISO 3166-1 (using extension/private codes for historic countries or regions that are not encoded in ISO 3166) Such registry should contain a search form for codes, showing the designs, the preferred aspect ratio metric, the color mappings, and if the flag itself is protected by some copyright restrictions (this won't limit the usage of fallback glyphs (showing letters in an enclosing blank flag) showing just the code in free fonts that do not want to violate these copyright restrictions, when they will still define some ligatures for flag designs that are free from those restrictions. But this registry does not have to be defined and maintained by the Unicode Consortium or by ISO, unless they have the desire to develop it. In any case, it is not necessary to make it part of the Unicode and ISO/IEC 10646 standards themselves (but there could be an informative reference to the registry, to help font developers.
