Unused ISO 3166-1 codes Almost all current ISO 3166-1 codes have been assigned and do exist in DNS. However, some of these are effectively unused. In particular, the ccTLDs for the Norwegian dependency
Bouvet Island (
bv) and the designation
Svalbard and Jan Mayen (
sj) do exist in DNS, but no subdomains have been assigned, and it is
Norid policy to not assign any at present. Two
French territories—
bl (
Saint Barthélemy) and
mf (
Saint Martin)— await local assignment by France's government. The code
eh, although eligible as ccTLD for
Western Sahara, has never been assigned and does not exist in
DNS. Only one subdomain is still registered in
gb (ISO 3166-1 for the
United Kingdom), and no new registrations are being accepted for it. Sites in the United Kingdom generally use
uk (see below). The former
.um ccTLD for the
U.S. Minor Outlying Islands was removed in April 2008. Under RFC 1591 rules,
.um is eligible as a ccTLD on request by the relevant governmental agency and local Internet user community.
ASCII ccTLDs not in ISO 3166-1 Several ASCII ccTLDs are in use that are not ISO 3166-1 two-letter codes. Some of these codes were specified in older versions of the ISO list. •
uk (
United Kingdom): The ISO 3166-1 code for the United Kingdom is GB. However, the
JANET network had already selected uk as a top-level identifier for its pre-existing
Name Registration Scheme, and this was incorporated into the DNS root.
gb was assigned with the intention of a transition, but this never occurred and the use of uk is now entrenched. •
su This obsolete ISO 3166 code for the
Soviet Union was assigned when the Soviet Union still existed; moreover, new su registrations are accepted. •
ac (
Ascension Island): This code is a vestige of
IANA's decision in 1996 to allow the use of codes reserved in the
ISO 3166-1 alpha-2 reserve list for use by the
Universal Postal Union. The decision was later reversed, with Ascension Island now the sole outlier. (Three other ccTLDs,
gg (
Guernsey),
im (
Isle of Man) and
je (
Jersey) also fell under this category from 1996 until they received corresponding ISO 3166 codes in March 2006.) •
eu (
European Union): On September 25, 2000,
ICANN decided to allow the use of any two-letter code in the
ISO 3166-1 reserve list that is reserved for all purposes. Only EU currently meets this criterion. Following a decision by the EU's Council of Telecommunications Ministers in March 2002, progress was slow, but a
registry (named
EURid) was chosen by the
European Commission, and criteria for allocation set:
ICANN approved
eu as a ccTLD, and it opened for registration on 7 December 2005 for the holders of prior rights. Since 7 April 2006, registration is open to all in the
European Economic Area.
Historical ccTLDs ccTLDs may be removed if that country ceases to exist. There are three ccTLDs that have been deleted after the corresponding 2-letter code was withdrawn from ISO 3166-1:
cs (for
Czechoslovakia),
zr (for
Zaire) and
tp (for
East Timor). There may be a significant delay between withdrawal from ISO 3166-1 and deletion from the DNS; for example, ZR ceased to be an ISO 3166-1 code in 1997, but the zr ccTLD was not deleted until 2001. Other ccTLDs corresponding to obsolete ISO 3166-1 codes have not yet been deleted. In some cases they may never be deleted due to the amount of disruption this would cause for a heavily used ccTLD. In particular, the Soviet Union's ccTLD
su remains in use more than twenty years after SU was removed from ISO 3166-1. The historical country codes
dd for the
German Democratic Republic and yd for
South Yemen were eligible for a ccTLD, but not allocated; see also
de and
ye. The temporary reassignment of country code cs (
Serbia and Montenegro) until its split into
rs and
me (
Serbia and
Montenegro, respectively) led to some controversies about the stability of ISO 3166-1 country codes, resulting in a second edition of ISO 3166-1 in 2007 with a guarantee that retired codes will not be reassigned for at least 50 years, and the replacement of RFC 3066 by RFC 4646 for country codes used in
language tags in 2006. The previous ISO 3166-1 code for
Yugoslavia, YU, was removed by ISO on 23 July 2003, but the
yu ccTLD remained in operation. Finally, after a two-year transition to Serbian
rs and Montenegrin
me, the .yu domain was phased out in March 2010. Australia was originally assigned the
oz country code, which was later changed to
au with the .oz domains moved to .oz.au. ==Internationalized ccTLDs==