South Korea’s Supreme Court on Thursday upheld prison sentences for three individuals convicted of violating the country’s National Security Act, including by engaging in illegal contact with North Korean operatives and organizing a pro-Pyongyang group.

The case concerns three South Korean activists who prosecutors say met in person with operatives from a cultural exchange bureau of Pyongyang’s Workers’ Party of Korea in China in May 2017, and again in Cambodia in April 2018.

The three were each sentenced to 12 years in prison during the first trial, but during the appeal received reduced sentences of between two and three years.