SEOUL, South Korea — Amid chaotic scenes, South Korea veered into uncharted legal and constitutional territory early Friday morning, as a group of investigators, backed by thousands of police, sought to arrest impeached President Yoon Suk Yeol.

No sitting South Korean president has ever been detained since the Republic of Korea was established in 1948.

Scuffles appeared to be underway inside the presidential residence between police and Presidential Security Personnel, confused and unclear reports from local media on the ground stated.

The Presidential Security Service – roughly equivalent to the U.S. Secret Service - have resisted previous attempts by police to enter presidential grounds to gather evidence.

Troops, possibly from the army’s Capital Defense Command, were also on site, apparently defending the residence against the investigators, who were backed by police.

Issues are being raised over who is in charge.

The president is the commander in chief of the armed forces, but Mr. Yoon has been impeached and his powers suspended. Acting President Choi Sang-mok, formerly Mr. Yoon’s finance minister, has made no apparent move.

Mr. Yoon is awaiting trial at the Constitutional Court, which is set to hold its second hearing into his case later Friday. The court has two prior presidential impeachments to draw upon as precedents.

The first-of-its-kind action underway at the presidential residence is being led by the relatively new Corruption Investigation Office for High-ranking Officials, The CIO has three times summoned Mr. Yoon for questioning, but he refused to comply with those summonses.

On Tuesday, the CIO was granted a court warrant to detain Mr. Yoon for up to 48 hours for questioning on charges of treason.

Treason is a crime for which a president cannot claim immunity. Mr. Yoon’s lawyers immediately took action to block the warrant.

“The execution of a warrant that is illegal and invalid is not lawful,” Yun Gap-geun, one of Mr. Yoon’s legal representatives, told media Friday, after news broke of this morning’s attempted seizure.

The court warrant expires Monday.

In expectation of investigators attempting an arrest, thousands of Mr. Yoon’s supporters had rallied nearby.

Mr. Yoon’s residence is in the swanky Seoul neighborhood of Hannam Dong, home to, among other well-to-do persons, members of supergroup BTS.

The number of pro-Yoon protesters, in freezing Thursday evening temperatures, was estimated at 10,000.

There has been widespread anticipation that investigative bodies, which include police and Ministry of Defense investigators as well as the CIO, would seek to fulfill their warrant before the weekend, when many more pro-Yoon protesters are expected to gather.

The CIO is a relatively new body that was established under the previous government of left-leaning President Moon Jae-in in 2021 amid a power struggle with Mr. Yoon.

Mr. Yoon had been made chief prosecutor in June 2019. In that position, he launched a corruption probe into Mr. Moon’s minister of justice. Mr. Moon also strongly resisted government demands for a reform of the state prosecution.

A prolonged political-judicial battle saw the resignation of two of Mr. Moon’s justice ministers.

With prosecution reform stalled, the entirely new CIO was proposed in December 2019 and established in January 2021.

Mr. Yoon stood down as head prosecutor in March 2021.

He was swiftly wooed by the right-wing party, who went on to choose him as its presidential candidate. In 2022, in a brand-new political career, Mr. Yoon won the presidential election by a margin of less than 1 percentage point.

Friday’s extraordinary events originate in Mr. Yoon’s stunning Dec. 3 declaration of martial law, prompted by obstructionism in the opposition-controlled parliament and by suspicions of electoral interference.

The botched attempted was voted down within three hours by lawmakers who made their way into the National Assembly through cordons of police and special forces troops. The decree was rescinded by Mr. Yoon six hours after his TV broadcast declaring it. Remarkably no injuries, let alone deaths, were reported in the coup fight.

Disgraced and disempowered, Mr. Yoon was impeached by the National Assembly vote on Dec. 14. His successor, Prime Minister Han Duck-soo, was subsequently impeached for refusing to sign off on the appointment of three judges to fill the Constitutional Court’s bench.

Mr. Han’s successor, Mr. Choi this week agreed on two of those judges, meaning the court now has eight of its nine seats filled.

At least six judges must vote to uphold impeachment of a president.

• Andrew Salmon can be reached at asalmon@washingtontimes.com.