SEOUL (Reuters) - South Korea on Monday banned the launching of propaganda leaflets into North Korea, drawing the criticism of rights activists and defiance from a prominent North Korean defector who said he would not stop sending messages to his homeland. Defectors and other campaigners in South Korea have for decades sent anti-North Korean leaflets over the tightly guarded border, usually by balloon or in bottles on border rivers. They also send food, medicine, money, mini radios and USB sticks containing South Korean news and dramas. Isolated North Korea has long denounced the practice and recently stepped up its condemnation of it, to the alarm of a South Korean government intent on improving ties on the divided peninsula. The South Korean parliament voted on Monday to amend the Development of Inter-Korean Relations Act to bar any scattering of printed materials, goods, money and other items of value across the heavily fortified frontier. It also restricts loudspeaker propaganda broadcasts, which the South’s military once championed as part of psychological warfare against the North until it withdrew the equipment following a 2018 summit between the two Koreas. The ban will take effect in three months and violators face up to three years in prison or 30 million won ($27,400) in fines. The change was approved despite efforts by opposition lawmakers to block the super-majority of the ruling party of President Moon Jae-in, who is keen to improve cross-border ties. FILE PHOTO: A balloon containing leaflets denouncing North Korean leader Kim Jong Un is seen near the demilitarized zone separating the two Koreas in Paju, South Korea, March 26, 2016. REUTERS/Kim Hong-Ji/File Photo CONSTITUTIONAL CHALLENGE The bill was introduced in June after Kim Yo Jong, the sister of North Korean leader Kim Jong Un, said South Korea should ban the leaflets or face the “worst phase” of relations. “They’re trying to put Kim Yo Jong’s order into law at her single word,” Tae Yong-ho, an opposition lawmaker and former North Korean diplomat, said in a 10-hour filibuster speech, adding the bill would only help Kim’s government continue “enslaving” its people. Park Sang-hak, a defector who has already been stripped of a license for his leaflet-launching group and faces a prosecution investigation, said he would not give up his 15-year campaign. “I’ll keep sending leaflets to tell the truth because North Koreans have the right to know,” he told Reuters. “I’m not afraid of being jailed”. Park and some other 20 rights groups in South Korea vowed to challenge the law’s constitutionality, while Human Rights Watch called the ban a “misguided strategy” by South Korea to win Kim’s favour. “It criminalises sending remittances to families in North Korea and denies their rights to outside information,” said Shin Hee-seok of the Transitional Justice Working Group. “Such appeasement efforts only risk inviting further North Korean provocations and demands.” Chris Smith, a U.S. Republican congressman co-chairing a bipartisan human rights commission, issued a statement criticising the amendment as “ill-conceived, frightening” for facilitating the imprisonment of people for simply sharing information. When asked about Smith’s statement, South Korean’s Unification Ministry, which handles ties with North Korea, said the bill was a “minimal effort to protect the lives and safety of residents in border regions”.