In the early hours of August 9, 2018, South Korean police stormed the home of Kim Ho, a thin, bespectacled, 46-year-old tech entrepreneur, in front of his three young children. He was charged under the National Security Act with leaking military secrets to North Korea, allegations he denied and imputed to “the brutality of public-security prosecutors.”

In 2007, while working in Beijing, Kim had hired engineers in North Korea to develop facial-recognition software. Kim later relied on that software to bid for a South Korean defense contract, but neglected to disclose the location of his engineers and allegedly did business with North Korean agents.

Kim was arrested amid the growing momentum of bilateral summits between Seoul and Pyongyang. South Korea’s Defense Acquisition Program Administration said that Kim had shared only a rough outline of the final project with his North Korean partners, not bona fide military secrets. In this context, his arrest under the National Security Act seemed wildly anachronistic, reminiscent of when the South Korean military regimes of the 1970s and ’80s used the law to violently quash leftist activists and silence political dissent.

Kim sought help from Minbyun (Lawyers for a Democratic Society), the South Korean equivalent of the ACLU. His case caught the eye of a veteran attorney named Jang Kyung-wook, nicknamed “the framed spy-case lawyer” for his high-profile exonerations of accused Communists, including a North Korean defector in 2013.

As Jang saw it, Kim was a most unlikely spy. In 2011, agents with South Korea’s National Intelligence Service (NIS) had groomed Kim as an asset, convincing him to provide them with a variety of intel: rice prices in North Korea, his chat logs with North Korean counterparts, and even North Korean software. “Were they giving him a tacit go-ahead?” Jang wondered. And for an alleged spy, Kim’s activities were perplexingly conspicuous. For example, he had applied for authorization to meet his North Korean business partner in 2007 in accordance with South Korean law, and had not bothered with alternate identities. In 2013, the NIS had Kim sign a nondisclosure agreement about their relationship. “If the NIS, which is supposed to be in charge of managing and deterring any kind of cyberterror risk, knew about this transaction, how can you say that there was a threat?” Jang added.

Jang’s broad, boyish features obscure a firebrand who has engaged in public swearing matches with much-feared NIS agents. His adversaries have reported him for legal malpractice, and conservatives roundly denounce him as a traitor and North Korean sympathizer. He is a leading proponent of the abolition of the National Security Act, which he and many other human-rights advocates regard as undemocratic and unconstitutional.

To Jang, the law is a Cold War–era relic with a troubling history of broad and arbitrary application. “The law was bloodstained and political from its birth,” he said. “It’s the ultimate ideological law, designed to drive North Korea and South Korea apart and to strike fear into people.” The National Security Act has been used to prosecute critics of the 30,000 troop-strong American military presence in South Korea as well as pro-unification civic groups.

Kim’s case is a reminder of South Korea’s seemingly intractable, homegrown McCarthyism—and the obstacle it poses to inter-Korean peace. But while past efforts to abolish the National Security Act under liberal administrations have been unsuccessful, the party of the current liberal president, Moon Jae-in, has hinted that reform may finally be possible.

The National Security Act dates back to the division of the Korean peninsula just after World War II. Syngman Rhee, South Korea’s first head of state and an anti-Communist autocrat backed by the United States, issued the law shortly after assuming office in 1948. He used it to consolidate power, arresting dissidents and carrying out political purges. Later, the military dictators of the 1970s and ’80s followed suit: They deployed the law to frame political opponents as spies, crush political activism, and suppress free speech.

Jang saw much of this firsthand, as did many of his peers of the “386 generation”—a term for South Koreans who were born in the 1960s and took part in the democracy movements in the 1980s. “In college, many friends of mine were taken away on National Security Act charges, mostly for reading forbidden material or for taking part in unification protests,” he said. “I was investigated for North Korea–related reading materials myself.” As a student activist, Jang referred his friends to lawyers at Minbyun: “That’s when I resolved to join Minbyun.”

The last serious effort to reform the National Security Act was made in 2004 by then-President Roh Moo-hyun, a leftist and Minbyun founding attorney. Roh had vowed on national television to put “the National Security Act in its sheath and send it to a museum,” but he couldn’t prevail over the conservative opposition.

Out of the hundred or so National Security Act cases Jang has had over his 20-year career, he is best known for helping to exonerate Yu Woo-sung, a North Korean defector and former Seoul municipal civil servant who was arrested in 2013. Yu Woo-sung’s younger sister, Yu Ga-ryeo, testified against him, but Jang proved in court that she’d lied and that she agreed to help the prosecution only after South Korean intelligence agents held her captive. “For six months, they beat and tortured her psychologically as they interrogated her about her brother,” Jang told me.

The Yu Woo-sung scandal gave the South Korean public a glimpse of the violence committed in the name of national security, and made Jang realize how the NIS, empowered by the National Security Act, produced innocent victims. “I didn’t fully grasp this system of manufacturing fake spies until I worked the Yu Woo-sung case, and learned about what the Joint Interrogation Complex did,” Jang said.

A drab NIS complex hemmed in by concrete walls and barbed wire on the outskirts of Seoul, the Joint Interrogation Complex is where defectors are screened before being settled in South Korea. “Defectors are subjected to intensive interrogation under the assumption that they might be spies,” Jang said. “Thus many of the accused spies are defectors.”

Veiled in secrecy and subject to little government oversight, this was where NIS agents tortured Ga-ryeo, but Jang said he believes she is far from the only one. “It’s South Korea’s Guantánamo Bay, but nobody had ever really objected to it or confronted it before. I was the first lawyer to even visit,” Jang said. After a public uproar, the complex was renamed the North Korean Defector Protection Center, but Jang remains skeptical of what goes on behind its walls.

The accusations against defectors reveal a deeper problem: that the law is inextricably bound up with the history of division and ongoing war. (The Korean War of 1950 to 1953 ended in an armistice, not a peace treaty.) “I don’t think that the National Security Act can be overcome simply by Western-style ideals of freedom of thought,” said attorney and former progressive politician Lee Jung-hee. “I think that, given the current state of the peninsula, as long as the greater majority of people believe that the enemy is right before our eyes…the National Security Act system will never fall apart.”

Jang sees the case against Kim as evidence that South Korea’s immense “spy-manufacturing machine” continues to whir, even amid gestures toward inter-Korean reconciliation. “People ask why this is happening under the Moon administration,” Jang said, noting that Moon was Roh’s protégé. “But that is because they don’t realize how deeply ingrained the NSA system is. Even under liberal governments, there are people who aren’t spies who have been caught in the system.” Much of this can be attributed to a culture of anti–North Korean paranoia in the Supreme Prosecutor’s Office. Although the agency has been subject to reform by the Moon administration, top-down reforms  can only do so much after a decade of corrupt governance. “The NSA is essentially a belief system that has infected the psyche of an entire country,” Jang told me.

Prosecutors claim that the Kim trial “isn’t an NSA case of an ideological nature, but one where an individual neglected national security in the course of pursuing personal profit.” Kim has protested this characterization in court, saying, “This case has exposed the arbitrariness of the National Security Act to the entire world. These public-security prosecutors have, in the manner of medieval witch hunters, contrived a spy charge under the pretense of national security.”

Following Kim’s arrest, South Korean police identified Kim as a former “leftist student activist,” drawing a line between his decades-old political views and his alleged treason. “The implication of dredging up that detail from his personal history a long time ago has ideological implications,” Jang said. “That somehow the defendant’s business decisions were motivated by an intent to help North Korea.”

Grassroots activist groups, spurred both by Kim’s case and the rapprochement with North Korea, have ramped up protests. The progressive Justice Party has called it “a law that has long since lost its validity and is all but waiting for a death sentence,” and announced plans to submit a bill for abolition, while demanding Kim Ho’s release. The Moon administration, on the other hand, seems cautious. Though a former Minbyun lawyer himself, Moon has kept quiet, cognizant that a partisan clash over the law could make negotiations with the North more difficult. Fellow Democratic Party lawmaker Lee Hae-chan called for a reappraisal of the law, but emphasized that talks between the United States and North Korea would have to progress further first. As another member of Moon’s party told South Korean media: “it’s not something to pursue this instant…. we still have trauma from [the failed abolition attempt] in 2004.”

Roh’s dead end in 2004 appears to inform this strategy of prioritizing the “regime of peace” before dealing with the National Security Act. Jang also believes that merely abolishing the law on paper would be cosmetic. “The NSA is premised on the Cold War–era logic of defining North Korea as an enemy of the state,” he said. “We need to first establish a state of peace where the threat of North Korea is no longer even a premise.”

What Jang is chafing against is something much bigger than the National Security Act. He views the enduring paranoia between North and South Korea as “the disease of division,” in which imagined spy plots thrive because people have become hesitant to challenge authority. “People have been conditioned by the security apparatus, and the real victims of the law are every citizen who has become afraid to think or say certain things. But that’s not something North Korea is doing to us, it’s something that’s being done to ourselves by our own hand.”