EU (European Union) country codes, ISO 3166-1 alpha-2. (This Gist is from 2012. Please see comments for updates.)

eu_country_codes.rb

# Note: VAT identification numbers for Greece use "EL", not "GR".

COUNTRY_CODES_EU = %w[
  AT BE BG CY CZ DK EE FI FR DE GR HU IE IT
  LV LT LU MT NL PL PT RO SK SI ES SE GB
]

@bradydan is it official in UK already? I will have peek on the E.U governing sites. I am aware of the EL reference for Greece (I am Greek) however the vast majority of services feed GR when they are US based, might be worth adding EL in any sense. Wikipedia cannot be trusted nowadays, I will look on the gov counterparts and amend where necessary once I can confirm. Thanks for taking the time to leave your comment fam.

@bradydan The UK adopted GDPR into the law when they left the EU.

I think this is an up to date 2022 list? https://www.defensorum.com/gdpr-countries-list/

I asked and answered this stack overflow question to come up with this list which I believe is up to date for 2022: AT, BE, BG, HR, CY, CZ, DK, EE, FI, FR, DE, EL, HU, IE, IT, LV, LT, LU, MT, NL, PL, PT, RO, SK, SI, ES, SE, UK

What a helpful thread! The list posted by Dan is almost right - UK is no longer part of the EU.

According to the UK government atleast: https://www.gov.uk/eu-eea
According to the canadian governement from 2013 (so needs modification): https://www23.statcan.gc.ca/imdb/p3VD.pl?Function=getVD&TVD=141329
According to the actual EU: https://european-union.europa.eu/easy-read_en

The alpha 2 code for Greece is GR no EL - which AFIK is not a valid Alpha2 code.
The correct list (with Alpha2 codes) would then be:

AT BE BG HR CY CZ DK EE FI FR DE GR HU IE IT LV LT LU MT NL PL PT RO SK SI ES SE

Cheers!

This thread was originally about EU countries, them @mizterp changed the topic to GDPR countries and it (confusingly) became a mixture of both topics.