Explained: Why South Korea's President Yoon faces impeachment over sudden martial law declaration

South Korean President Yoon Suk Yeol faced growing legislative and public pressure to resign or be removed from office on Wednesday, following the abrupt end of a brief martial law declaration. The controversial move had prompted troops to surround parliament, only for lawmakers to swiftly vote to revoke it.

In the aftermath, Yoon’s senior advisers and secretaries tendered their collective resignations, while Cabinet members, including Defense Minister Kim Yong Hyun, faced mounting calls to step down. The nation remained in turmoil, grappling with the fallout of what many perceived as a poorly conceived political maneuver.

In the capital, life appeared largely unaffected by the political turmoil. Tourists and residents strolled through the streets, traffic and construction noises filled the air, and, apart from clusters of shield-bearing police, it seemed like an ordinary sunny yet cold December morning.

The chaos stemmed from President Yoon Suk Yeol’s sudden imposition of emergency martial law on Tuesday night. Justifying the move as a crackdown on “anti-state” forces, Yoon acted after facing resistance to his agenda in the opposition-controlled parliament. However, the declaration lasted barely six hours, as the National Assembly swiftly voted to overrule him. The martial law was formally lifted during a Cabinet meeting at around 4:30 a.m.

On Wednesday, the opposition Democratic Party, which holds a majority in the 300-seat parliament, announced its decision to demand Yoon’s immediate resignation. They put forward a motion to impeach President Yoon over his botched attempt late on Tuesday to impose martial law. The motion will still need to be debated before going to a vote, possibly later this week.

“President Yoon Suk Yeol’s martial law declaration was a clear violation of the constitution. It didn’t abide by any requirements to declare it,” the Democratic Party said in a statement. “His martial law declaration was originally invalid and a grave violation of the constitution. It was a grave act of rebellion and provides perfect grounds for his impeachment.”

Constitutional Controversy: Impeachment Demands and Legal Challenges

Impeaching President Yoon Suk Yeol would require the support of two-thirds of the 300-member National Assembly—200 votes. The Democratic Party and smaller opposition groups collectively hold 192 seats. However, when parliament rejected Yoon’s martial law declaration in a 190-0 vote, 18 lawmakers from Yoon’s own People Power Party backed the rejection, according to National Assembly officials.

Han Dong-hun, leader of the People Power Party and a long-time ally of Yoon from their days as prosecutors, condemned the martial law declaration as “unconstitutional.” If impeachment proceedings succeed, Yoon would be stripped of his presidential powers pending a ruling by the Constitutional Court. During that time, Prime Minister Han Duck-soo, the second-highest-ranking official in South Korea’s government, would assume presidential duties.

Amid growing demands for the Cabinet to resign, Prime Minister Han urged calm in a public statement, calling on Cabinet members to “continue fulfilling your duties even in this challenging moment.”

President Yoon Suk Yeol’s martial law declaration—the first in more than 40 years—evoked memories of South Korea’s authoritarian past, when military-backed governments used such measures to deploy soldiers, tanks, and armored vehicles to suppress dissent. These scenes, absent since South Korea’s transition to democracy in the late 1980s, reappeared briefly on Tuesday night.

Following Yoon’s decree, troops in full battle gear, armed with assault rifles, were deployed to block protesters from the National Assembly as military helicopters hovered overhead and landed nearby. In one tense moment, a soldier reportedly pointed a rifle at a woman protesting outside the building, where demonstrators were calling for an immediate end to the martial law.

Despite the heavy military presence, it remains unclear how 190 lawmakers managed to enter the parliamentary hall to vote down the decree. Opposition leader Lee Jae-myung livestreamed himself climbing over a wall, while some lawmakers were blocked by troops and police. Others, however, were allowed to pass without significant resistance.

No major violence was reported, and after the parliamentary vote to overturn the martial law, troops and police were seen withdrawing from the National Assembly grounds. National Assembly Speaker Woo Won Shik commented on the day's events, saying, “Even with our unfortunate memories of military coups, our citizens witnessed today the maturity of our military.”

Han Dong-hun, leader of the ruling People Power Party, demanded that President Yoon Suk Yeol justify his decision to impose martial law and called for the dismissal of Defense Minister Kim Yong Hyun, whom he accused of advising Yoon to take the drastic measure. The Defense Ministry has yet to comment on the matter.

Under South Korea’s constitution, the president is permitted to declare martial law during “wartime, war-like situations, or comparable national emergencies” that necessitate military intervention to restrict freedoms such as press and assembly to maintain order. However, many observers question whether the current political climate qualifies as such a state. The constitution also mandates that the president must comply if the National Assembly votes by majority to lift martial law.

Domestic and International Reactions: Military Intervention and Global Concern

Experts have raised concerns that Yoon may have violated constitutional provisions in implementing martial law. While martial law permits "special measures" restricting freedoms and limiting agency and court authority, it does not allow interference with the functions of parliament. Yet, following Yoon’s order on Tuesday, South Korea’s military announced the suspension of parliamentary activities and stationed troops to block lawmakers from entering the National Assembly.

Democratic Party floor leader Park Chan-dae called for an immediate investigation into Yoon on charges of rebellion, citing his deployment of troops to obstruct parliament. Although South Korean presidents generally have immunity from prosecution while in office, this protection does not cover allegations of rebellion or treason.

In Washington, the White House expressed "serious concern" over the events in Seoul. A National Security Council spokesperson stated that the Biden administration was not notified in advance of Yoon’s martial law declaration and was in contact with the South Korean government. Meanwhile, Pentagon spokesman Maj. Gen. Pat Ryder confirmed there was no impact on the more than 27,000 US troops stationed in South Korea.

President Yoon Suk Yeol's administration and the ruling People Power Party have been locked in a political standoff with the Democratic Party over next year’s budget bill and the opposition’s push to impeach three senior prosecutors.

In his televised address announcing the martial law, Yoon referred to the opposition as “shameless pro-North Korean anti-state forces who are plundering the freedom and happiness of our citizens,” though he did not provide further details. North Korea has yet to comment on the situation.

Natalia Slavney, a research analyst at the Stimson Center’s 38 North, which focuses on Korean affairs, described President Yoon’s imposition of martial law as "a serious backslide of democracy" and part of a "worrying trend of abuse" since he took office in 2022.

Slavney emphasized that South Korea has a strong tradition of political pluralism and is no stranger to mass protests and swift impeachments. She pointed to the case of former President Park Geun-hye, who was removed from office and imprisoned in 2017 on charges of bribery and other crimes, though she was later pardoned.