South Korea has banned 21 Americans convicted of sex crimes against children from entering the country.

South Korea’s Justice Ministry says it took the measure after U.S. authorities provided a list of convicted pedophiles who have a high probability of travel to Asia. A statement Thursday said it is the first time South Korea has imposed an entry ban on foreign pedophiles.

The ministry says the measure is aimed at protecting Korean youths from sexual violence involving foreigners. It said some American pedophiles have worked as English teachers in South Korea.

A suspected Canadian pedophile worked at South Korean schools for several years before being arrested in Thailand in October following a global manhunt.