The ruling People Power Party(PPP) has called for an immediate investigation into the head of the Corruption Investigation Office for High-ranking Officials(CIO), Oh Dong-woon, claiming that the agency’s probe into President Yoon Suk Yeol was unlawful.

PPP spokesperson Shin Dong-uk made the demand on Sunday, asserting that the CIO had no authority to investigate insurrection cases and had "shopped" for a court that would issue an arrest warrant for Yoon.

The spokesperson said that the public are now questioning whether the unprecedented illegal arrest and detention of a sitting president, driven by the CIO’s excessive investigation, constitutes a disruption of national order and an act of insurrection.

The call for an investigation came after Yoon was released on Saturday, following a local court's decision to revoke his detention after 52 days in custody.

The ruling party also pressed the Constitutional Court to adhere to due process while some lawmakers called on the court to dismiss Yoon’s impeachment in light of the ruling.

PPP floor leader Kweon Seong-dong said that if the Constitutional Court considers the court's decision and determines that there were shortcomings in the due process, it would be necessary to reopen arguments in Yoon’s impeachment trial.