Justices of the Constitutional Court stand inside the courtroom ahead of a verdict on the constitutionality of the anti-leaflet law at the court in Seoul, Tuesday. Yonhap

The Constitutional Court ruled on Tuesday that a law banning the sending of anti-Pyongyang leaflets across the inter-Korean border is unconstitutional, siding with human rights activists calling for its abolition on the grounds of freedom of speech.

The court said the law violates the constitutional right to freedom of expression, with seven of the nine justices ruling it unconstitutional, after nearly three years of deliberation on the case.

"Restricting the content of expression is allowed only when, in principle, doing so is inevitable for (protecting) the significant public interest," the court said. "Strict standards should be applied, especially when restricting political expressions based on certain position, ideology or perspective."

The law, under which violators could face up to three years in prison or a maximum fine of 30 million won ($23,000), demonstrates the state's excessive punishment powers as it would penalize even the attempt of such activities, the court added.

The court also said that the leaflet campaigners should not be burdened with the responsibility regarding the public's safety as it is the North Korean regime that is fully responsible for it.

Rep. Tae Yong-ho, a defector-turned lawmaker and one of the most vocal critics of the law, welcomed the ruling, saying in a statement that the main opposition Democratic Party of Korea (DPK) should take responsibility for creating the problematic law in the first place.

The ruling is a victory for rights advocates, who have campaigned against the injustice of the law. They said the law, enacted in 2020 during the previous administration, after Pyongyang threatened retaliation over the sending of such materials, deprived the basic right to the truth.

The verdict is aligned with the ruling of the Supreme Court. It overturned a lower court decision that justified the Unification Ministry's move to revoke a rights group's license over security concerns surrounding its campaign to send balloons filled with anti-regime leaflets to the North.

After two fruitless summits with the U.S., Kim Yo-jong, North Korea's propaganda operation chief and the sister of leader Kim Jong-un, threatened in June 2020 to revoke the peace accords with Seoul over the leaflet campaign. By the end of that year, lawmakers of the then-governing DPK unilaterally approved the bill in response to her demand at the National Assembly, where it held a majority, claiming that sending such leaflets into North Korea would pose a risk to the safety of the residents living near the border.

The legislative action immediately drew condemnation from rights experts at U.N. agencies and international NGOs. The law is a clear violation of multiple U.N. treaties that guarantee the rights to freedom of speech and association, they said.

The International Covenant on Civil and Political Rights, for example, says everyone has the right to freedom of expression, which includes the “freedom to seek, receive and impart information and ideas of all kinds, regardless of frontiers, either orally, in writing or in print, in the form of art, or through any other media of his choice.” As one of the ratifying states, South Korea's laws should comply with the provisions.

On the same day, the Constitutional Court also ruled that Article 7 of the National Security Act was constitutional. The law stipulates that a person who knowingly praises, incites or propagates the activities of an anti-government organization or an individual can be punished by up to seven years in prison.

Since its last amendment in 1991, the law has been reviewed and ruled constitutional by the court eight times including this time.