I'm trying to understand why some territories have flag emojis and others don't.

Wikipedia ( https://en.wikipedia.org/wiki/Regional_indicator_symbol ) tells me it's based on Unicode region codes, which include:

"6 exceptional reservations (Ascension Island, Clipperton Island, Diego Garcia, Ceuta and Melilla, Canary Islands, and Tristan da Cunha)"

I can't seem to find any information on why these specific territories have been added, and it's very puzzling to me.

Regional indicator symbol - Wikipedia

@mhalila His book on emoji doesn't delve into detail about flag emojis but @shadychars might know something about it (or at least who to ask)
@tiikerikani @mhalila Hi both - Ireland and Germany produced a doc on which flags should be encoded back in 2009: https://www.unicode.org/L2/L2009/09318-n3680-countrycodes.pdf. That doc proposed using ISO 3166 as a source for countries/territories to be encoded in Unicode, and ISO 3166 in turn has those exceptions (Ascension Island, Diego Garcia etc.).
@tiikerikani @mhalila I haven't followed that first doc in detail to see whether it was adopted, but it does look like Unicode was content to use ISO 3166 as a guide.
@tiikerikani @mhalila ISO has a tool where you can look up country codes: https://www.iso.org/obp/ui/#iso:pub:PUB500001:en. If you take a look there, most of those "exceptionally reserved" places are there at the request of the Universal Postal Union or the International Telecommunication Union.
@shadychars @tiikerikani thank you so much! This is exactly what I was looking for.
@mhalila @tiikerikani No problem at all!