UTR#51 actually uses Unicode CLDR region codes for legal/required pairs of Regional Indicator Symbol Letters U+1F1E6–FF, but they are virtually identical to current ISO 3166-1 alpha-2 code elements. Some codes, however, had once been part of ISO 3166 but have since been deleted (and either exceptionally or transitionally reserved) or are indeterminately reserved for compatibility with other international standards. Some exceptional reservations are part of CLDR. Most transitional reservations now have ISO 3166-3 alpha-4 codes, which Unicode does not intend to support. Indeterminate reservations have been very rarely assigned to new countries and this probably won’t happen again.
Anyhow, many of the currently reserved codes would be represented by flag emojis that are frequently requested and are not covered by the recent amendment to UTR#51 to encode ISO 3166-2 subregions with Emoji Tag Sequences (based on and falling back to a flag emoji, 🏳). It would therefore be relatively safe and quite welcome to support these codes.
| Code | Region | Related region | Status |
|---|---|---|---|
| 🇦🇨 | Ascension Island | 🇬🇧 | in CLDR and Emoji ≤3.0 |
| 🇦🇮 | French Afar and Issas = Djibouti | 🇩🇯 | AIDJ, → Anguilla |
| 🇦🇳 | Netherlands Antilles | 🇧🇶 🇨🇼 🇸🇽 | ANHH |
| 🇦🇵 | African Regional Industrial Property Organization | … | WIPO ST.3 |
| 🇧🇶 | British Antarctic Territory | 🇦🇶 | BQAQ, → Bonaire, Sint Eustatius and Saba |
| 🇧🇺 | Burma = Myanmar | 🇲🇲 | BUMM |
| 🇧🇽 | Benelux Trademarks and Design Offices | 🇧🇪 🇳🇱 🇱🇺 | WIPO ST.3 |
| 🇨🇵 | Clipperton Island | 🇫🇷 | in CLDR and Emoji ≤3.0 |
| 🇨🇸 | Czechoslovakia | 🇨🇿 🇸🇰 | CSXX, → Serbia and Montenegro |
| 🇨🇸 | Serbia and Montenegro | 🇲🇪 🇷🇸 | CSHH |
| 🇨🇹 | Canton and Enderbury Islands = Kiribati | 🇰🇮 | CTKI |
| 🇩🇩 | German Democratic Republic | 🇩🇪 | DDDE |
| 🇩🇬 | Diego Garcia | 🇬🇧 | in CLDR and Emoji ≤3.0 |
| 🇩🇾 | Dahomey = Benin | 🇧🇯 | DYBJ |
| 🇪🇦 | Ceuta, Melilla | 🇪🇸 | in CLDR and Emoji ≤3.0 |
| 🇪🇫 | Union of Countries under the European Community Patent Convention | 🇪🇺 | WIPO ST.3 |
| 🇪🇲 | European Trademark Office | 🇪🇺… | WIPO ST.3 |
| 🇪🇵 | European Patent Organization | 🇪🇺… | WIPO ST.3 |
| 🇪🇺 | European Union | … | in CLDR and Emoji 3.0 |
| 🇪🇻 | Eurasian Patent Organization | 🇷🇺… | WIPO ST.3 |
| 🇪🇼 | Estonia | 🇪🇪 | EE |
| 🇪🇿 | Eurozone | 🇪🇺 | — |
| 🇫🇱 | (Fürstentum) Liechtenstein | 🇱🇮 | LI |
| 🇫🇶 | French Southern and Antarctic Territories | 🇹🇫 | FQHH |
| 🇫🇽 | Metropolitan France | 🇫🇷 | FXFR |
| 🇬🇨 | Patent Office of the Cooperation Council for the Arab States of the Gulf (GCC) | 🇸🇦… | WIPO ST.3 |
| 🇬🇪 | Gilbert and Ellice Islands | 🇰🇮 🇹🇻 | GEHH, → Georgia |
| 🇭🇻 | Upper Volta = Burkina Faso | 🇧🇫 | HVBF |
| 🇮🇧 | International Bureau of WIPO | 🇺🇳 | WIPO ST.3 |
| 🇮🇨 | Canary Islands | 🇪🇸 | in CLDR and Emoji ≤3.0 |
| 🇯🇦 | Jamaica | 🇯🇲 | JM |
| 🇯🇹 | Johnston Island | 🇺🇲 | JTUM |
| 🇱🇫 | Libya Fezzan | 🇱🇾 | LY |
| 🇱🇹 | Libya Tripoli | 🇱🇾 | → Lithuania |
| 🇲🇪 | Western Sahara | 🇪🇭 | → Montenegro |
| 🇲🇮 | Midway Islands | 🇺🇲 | MIUM |
| 🇳🇭 | New Hebrides = Vanuatu | 🇻🇺 | NHVU |
| 🇳🇶 | Dronning Maud Land | 🇦🇶 🇳🇴 | NQAQ |
| 🇳🇹 | Neutral Zone | 🇮🇶 🇸🇦 | NTHH |
| 🇴🇦 | African Intellectual Property Organization | … | WIPO ST.3 |
| 🇵🇨 | Pacific Islands, Trust Territory of the | 🇫🇲 🇲🇭 🇵🇼 🇲🇵 | PCHH |
| 🇵🇮 | Philippines | 🇵🇭 | PH |
| 🇵🇺 | US Miscellaneous Pacific Islands | 🇺🇲 | PUUM |
| 🇵🇿 | Panama Canal Zone | 🇵🇦 | PZPA |
| 🇷🇦 | Argentina | 🇦🇷 | AR |
| 🇷🇧 | Bolivia | 🇧🇴 | BO |
| 🇷🇧 | Botswana | 🇧🇼 | BW |
| 🇷🇨 | (Republic of) China = Taiwan | 🇹🇼 | TW |
| 🇷🇭 | (Southern) Rhodesia | 🇿🇼 | RHZW |
| 🇷🇭 | Haiti | 🇭🇹 | HT |
| 🇷🇮 | Indonesia | 🇮🇩 | ID |
| 🇷🇱 | Lebanon | 🇱🇧 | LB |
| 🇷🇲 | Madagascar | 🇲🇬 | MG |
| 🇷🇳 | Niger | 🇳🇪 | NE |
| 🇷🇵 | Philippines | 🇵🇭 | PH |
| 🇷🇺 | Burundi | 🇧🇮 | → Russian Federation |
| 🇸🇫 | Finland = Suomi | 🇫🇮 | FI |
| 🇸🇰 | Sikkim | 🇮🇳 | SKIN, → Slovakia |
| 🇸🇺 | Soviet Union | 🇷🇺🇦🇲🇦🇿🇧🇾🇪🇪🇬🇪🇰🇿🇰🇬🇱🇻🇱🇹🇲🇩🇹🇯🇹🇲🇺🇦🇺🇿 | SUHH, still a ccTLD |
| 🇹🇦 | Tristan da Cunha | 🇬🇧 | in CLDR and Emoji ≤3.0 |
| 🇹🇵 | East Timor = Timor-Leste | 🇹🇱 | TPTL |
| 🇺🇰 | United Kingdom | 🇬🇧 | ccTLD (ISO/CLDR use GB instead) |
| 🇺🇳 | United Nations | … | in CLDR and Emoji 4.0 |
| 🇻🇩 | Democratic Republic of (North) Viet-Nam | 🇻🇳 | VDVN |
| 🇼🇬 | Grenada | 🇬🇩 | GD |
| 🇼🇰 | Wake Island | 🇺🇲 | WKUM |
| 🇼🇱 | Saint Lucia | 🇱🇨 | LC |
| 🇼🇴 | World Intellectual Property Organization | 🇺🇳 | WIPO ST.3 |
| 🇼🇻 | Saint Vincent | 🇻🇨 | VC |
| 🇾🇩 | Democratic (South) Yemen | 🇾🇪 | YDYE |
| 🇾🇺 | Yugoslavia | 🇲🇪 🇷🇸 🇧🇦 🇭🇷 🇸🇮 🇲🇰 🇽🇰 | YUCS, still a ccTLD |
| 🇾🇻 | Venezuela | 🇻🇪 | VE |
| 🇿🇷 | Zaire = Congo | 🇨🇩 | ZRCD |