The South Korean Parliament passed a bill Monday that prohibits the launching of propaganda leaflets across the border into North Korea.

For decades, South Korean defectors and campaigners sent anti-North Korean leaflets, as well as food, medicine, money, and USB sticks containing South Korean news and dramas, across the border to North Korea. They used balloons or bottles to transport the materials.

North Korea has long denounced the leafletting. Kim Yo Jong, the sister of North Korean leader Kim Jong Un, told South Korea to ban the leaflets or face the “worst phase of relations.” In June, a bill to ban the leafletting was introduced in parliament.

On Monday, the South Korean Parliament passed the bill in a 187-0 vote. The bill will amend the Development of Inter-Korean Relations Act, and it prohibits the distribution of printed materials, goods, money, and other items across the border. It also restricts loudspeaker propaganda broadcasts.

Violators can be punished with up to three years in prison or a maximum fine of 30 million won (USD $27,000).

This bill has drawn criticism from a variety of sources. On December 5, Human Rights Watch (HRW) called on South Korea to reject the bill, stating that the law would violate South Korean individuals’ rights to freedom of expression and would “make engaging in humanitarianism and human rights activism a criminal offense.”