By law, a Korean-born U.S. citizen’s South Korean passport is automatically void once the citizenship has been obtained.
According to the Korean consulate office in L.A., at least one U.S. citizen is caught using a South Korean passport in Korea. Such violation warrants a fine of roughly about $2,000.
The South Korean law stipulates that all of its citizens who have naturalized in another country are no longer eligible to use their South Korean passport. Also, anyone who forfeits South Korean citizenship is no longer allowed to travel with a passport issued by the Korean government.
In addition, South Korean citizens who later change their nationality are encouraged to report to the Korean government about their status, but the participation rate so far has not been high.
“A U.S. citizen who boards an airplane with a South Korean passport could easily be found by a quick background search at the airport,” said the Korean consulate office in L.A.