
It is the right of all countries to protect its national interest. Entry inspection of foreigners is one such carnation of the right, which is incidentally one of the key functions of the immigration administration.
Its main purpose is to prevent entry by foreigners who are banned or trying to enter through illegal means.
Hence foreigners trying to use forged or altered passports, deemed as having questionable purpose of entry or inviting parties, or otherwise are using illegal means to gain entry may be denied entry into Korea at any time.