Explainer-What you need to know about the arrest of South Korea's Yoon

By Hyonhee Shin

SEOUL (Reuters) - South Korean investigators arrested impeached President Yoon Suk Yeol on Wednesday for alleged insurrection over his bid to impose martial law, after weeks of defiance and claims by Yoon and his lawyers that the arrest warrant was invalid.

Here is what we know about his arrest so far:

WHY WAS YOON ARRESTED?

Yoon's arrest stems from his brief imposition of martial law on Dec. 3, which stunned South Koreans as he declared on national television his aim to root out "anti-state forces" and to overcome political deadlock.

But after about six hours, he abandoned the plan after staffers at parliament used barricades and fire extinguishers to ward off soldiers trying to prevent lawmakers from voting to reject Yoon's declaration.

Parliament voted to impeach Yoon on Dec. 14 and a trial at the Constitutional Court is underway to decide his political future, but investigators also launched a criminal probe into allegations of insurrection.

This is one of the few criminal charges from which a South Korean president does not have immunity and when Yoon ignored summons for questioning, a court approved an arrest warrant on Dec. 31, which was later extended.

A first attempt to arrest him was blocked by presidential guards at his hillside villa before he was taken into custody on Wednesday.

WHO ARE THE INVESTIGATORS?

The Corruption Investigation Office for High-Ranking Officials (CIO) is leading the joint investigation team involving police and the defence ministry, while prosecutors also carry out their own probe.

The CIO was launched in 2021 as an independent anti-graft agency to investigate high-ranking officials, including the president, and their family members.

But its investigating and prosecuting rights are limited. It does not have the authority to prosecute the president and is required to refer the case to the prosecutors' office to take any action, including indictment, once questioning is over.

The investigators now have 48 hours to question Yoon, before seeking a warrant to detain him for up to 20 days or to release him.

WHAT IS YOON'S ARGUMENT?

Yoon said on Wednesday that he submitted himself for questioning to avoid any bloodshed despite what he called the illegality of the investigation and arrest.

Yoon's lawyers have said that unlike prosecutors, the CIO does not have the authority to handle his case as the law stipulates a wide-ranging list of high-ranking officials and violations it can investigate, but has no mention of insurrection.

The lawyers also said that the arrest warrant was unconstitutional because it was granted by a court in the wrong jurisdiction.

They said any criminal investigation should be conducted after the Constitutional Court holds a trial on Yoon's impeachment and decides whether to remove him from office permanently.

Yoon's team has filed a complaint and an injunction with the Constitutional Court to review the warrant's legitimacy.

WHAT IS THE POSITION OF THE CIO, POLICE?

The CIO has said it has secured the rights to take on Yoon's case by obtaining the arrest warrant, but apologised for previously failing to arrest Yoon and requested police to take over execution of the warrant.

Ahead of Yoon's arrest, police acknowledged that there was a legal dispute over the case but held multiple meetings with the CIO to discuss how to execute the warrant after securing a re-issued arrest warrant on Jan. 7.

Seok Dong-hyeon, Yoon's legal advisor, has said the bid to transfer execution of the warrant to the police was effectively an admission by the CIO that its probe and the warrant were "illegal".

WHAT DO COURTS SAY?

The Constitutional Court said on Monday it is reviewing the complaint and injunction filed by Yoon's lawyers.

The Seoul Western District Court, dismissing a similar complaint previously, said that it was not illegal for the CIO to handle Yoon's case as allegations of insurrection are included in abuse of power charges covered by the agency.

Yoon's lawyers criticised the court's statement as "sophistry" and said they will consider appealing the decision to a higher court.

(Reporting by Hyonhee Shin; Editing by Ed Davies, Michael Perry and Raju Gopalakrishnan)