The BTS members were appointed as Future Culture Special Envoys by former South Korean president, Moon Jae In. In addition to their letters of appointment and commemorative fountain pens, each member received a diplomatic passport.
BTS and President Moon | @charts_k/Twitter
Diplomatic passports give their holders benefits that people with regular passports don’t have. As such, only certain people have diplomatic passports in South Korea, including the President, Prime Minister, Speaker of the National Assembly, Chief Justice of the Supreme Court, Foreign Minister, former presidents and their families, former prime ministers and their families, and civil servants appointed by the Foreign Minister. Special envoys, like BTS, can also receive diplomatic passports in accordance with the Enforcement Decree of the Passport Act.
With their diplomatic passports, BTS receives visa exemption from 199 countries, which means the members will be able to enter those countries without visas. They also have diplomatic immunity as special envoys and holders of diplomatic passports. Diplomatic immunity means they cannot be prosecuted for crimes while travelling on official business, allowing them to properly represent their country.
Since people with diplomatic passports must use their regular passports for personal travel, BTS can only use their new passports when entering and leaving South Korea for special diplomatic activities. The members much use their personal passports for vacations, tours, and other non-diplomatic events, like overseas award shows.
Should they be travelling using their diplomatic passport, other benefits extended include tax-free and duty-free purchases while in another country. They would also be exempt from any sort of search that local authorities would want to attempt in order to focus on their responsibilities as a diplomat.