
President Yoon Suk Yeol is taken to the Seoul Detention Center after being grilled over his declaration of martial law at the Corruption Investigation Office for High-ranking Officials in Gwacheon, Gyeonggi Province, Wednesday. Newsis
President Yoon Suk Yeol refused to be questioned by the Corruption Investigation Office for High-ranking Officials (CIO), Thursday, over his martial law declaration, with his lawyers saying that he will not cooperate with any investigation by the agency, as they believe it lacks the legal authority to conduct such an inquiry.
According to Seok Dong-hyun, a member of the president's defense team, Yoon had nothing more to add after a 10-hour interrogation conducted by CIO investigators the previous day and would not respond to any further requests for questioning.
"There is no reason or necessity to cooperate with the CIO's illegal investigation," Seok said.
Yoon was detained on Wednesday morning at his residence in Seoul by investigators from the CIO and the police and underwent two questioning sessions at the agency's headquarters. Afterward, he was placed in the Seoul Detention Center.
Earlier on Thursday, Yoon was scheduled to be questioned in the morning, but the session was postponed to 2 p.m. after his lawyers cited health reasons. Ultimately, he did not appear for the afternoon interrogation.
Before Yoon was brought to its headquarters in Gwacheon, Gyeonggi Province, the CIO had over 200 pages of inquiries prepared. He is accused of two main criminal offenses ― abuse of power and insurrection ― stemming from his actions in authorizing and implementing the martial law decree.
Yet Yoon has mostly remained silent, refusing to give any meaningful responses, according to the CIO. At the end of the first day of interrogation, he even declined to sign the document required to confirm the due process of the questioning.
His lawyers contend that the CIO lacks the legal authority to investigate accusations of insurrection. They cite a law explicitly designating the police as the sole authority to handle such matters. However, the CIO maintains its investigative jurisdiction, arguing that insurrection constitutes a related crime within the scope of its authority.
For that reason, Yoon's legal team argues that the warrant issued to detain him by what they describe as a "left-leaning" judge, Lee Soon-hyung, at the Seoul Western District Court, was flawed from the outset.
The legal team brought the issue before the Seoul Central District Court, where Judge So Joon-sub began a hearing at about 5:08 p.m. to determine whether the legal procedure for issuing the detention warrant was lawful.

Supporters of President Yoon Suk Yeol hold a rally near the Seoul Detention Center in Uiwang, Gyeonggi Province, Thursday. Newsis
After detaining Yoon, the CIO had 48 hours to decide whether to apply for a separate warrant to formally arrest him. Typically, investigators seek arrest warrants for suspects of serious crimes after taking them into custody first.
However, with the legitimacy of its initial detention warrant under scrutiny, the CIO suggested it may delay its decision until the court rules on the matter. This means the agency could apply for an arrest warrant after 10:33 a.m. Friday, which is exactly 48 hours after Yoon's detention. However, the president can be held a bit longer, as the time spent on the court's review of the detention warrant will not be counted, according to the CIO.
If an arrest warrant is issued for Yoon, the CIO has 20 days before an indictment. Since the prosecution holds the right to indict a president, the two institutions have agreed that the CIO investigation will be concluded within the first 10 days and the case will then be handed over to prosecutors.
One of the key objectives of the investigators is to find out whether he had a clear intention to incite violence with the goal of "excluding national power from all or part of the territory" of the country, or of "subverting the Constitution" ― the definition of insurrection, a charge punishable by death. Critics say a violent attempt to paralyze the operation of the National Assembly could qualify as such, accusing Yoon of having told martial law troops to remove lawmakers from the Assembly to prevent them from voting to lift the decree.