Police officers guard the main entrance of the Constitutional Court in Jongno District, Seoul, Friday. Yonhap

The nation's two main political parties are clashing over the opposition bloc's decision to exclude insurrection charges as grounds for President Yoon Suk Yeol's impeachment at the Constitutional Court, lawmakers and political watchers said on Sunday.

The main opposition Democratic Party of Korea (DPK) argued that the revision was necessary to expedite court proceedings while the ruling People Power Party (PPP) criticized the change, claiming it highlights the legal flaws in the impeachment motion and thus the motion should be nullified.

At the second preparatory hearing at the Constitutional Court on Friday, legal representatives of the National Assembly's impeachment investigation committee, which acts as the prosecution in the trial, announced they would withdraw the insurrection charges as a key factor in Yoon's impeachment. Instead, the committee decided to focus on whether Yoon's declaration of martial law violated the Constitution.

Yoon's legal team objected, insisting that "evidence regarding the treason charge must be thoroughly examined, as it is the focal point of public attention."

The court is expected to discuss whether insurrection will remain part of the impeachment trial during a meeting on Monday. It will mark the first gathering of all eight justices after two new members — Jeong Gye-seon and Cho Han-chang — took office on Thursday.

The first formal hearing for Yoon's trial is set for Jan. 14, with additional sessions scheduled for Jan. 16, 21, 23 and Feb. 4. Yoon is required to attend the hearings.

Yoon's lawyer Yun Gap-geun said Sunday that the president "will attend a hearing at an appropriate time and express his views," without specifying when.

Rep. Jung Chung-rae of the main opposition Democratic Party of Korea, left, along with legal representatives of the National Assembly's impeachment investigation committee, attend the second preparatory hearing at the Constitutional Court in Seoul, Friday. Joint Press Corps

The president is on trial after the National Assembly impeached him on Dec. 14 for his brief imposition of martial law on Dec. 3.

The impeachment motion, filed by the opposition bloc, accused Yoon of "committing insurrection that jeopardized national peace by staging a riot." It also argued that his deployment of the military and police forces during the martial law incident threatened the Assembly and the public's safety, and that the declaration of emergency military rule itself violated the Constitution.

PPP floor leader Kweon Seong-dong criticized the opposition's decision to remove the insurrection charges, saying, "The court should dismiss this hastily prepared impeachment motion and require the Assembly to reconvene and vote on a properly drafted one."

"The word 'insurrection' appears 38 times in the impeachment motion, and the first listed reason is insurrection-related criminal acts," Kweon said on Saturday. "Insurrection allegations were the alpha and omega of the impeachment motion. Without it, the motion is meaningless."

The DPK refuted Kweon's claim, calling it "delusional."

"The PPP is clearly mixing up reality with a fantasy," DPK spokesperson Rep. Han Min-soo said on Sunday. "The grounds for impeachment had to be adjusted so that the court can focus on constitutional violations, rather than criminal charges, in the impeachment trial."

Han also noted that Kweon, who led the Assembly's impeachment committee during former President Park Geun-hye's impeachment trial in 2017, had made similar revisions by excluding bribery and coercion charges in reasons for her removal to simplify the court proceedings.

Rep. Kweon Seong-dong, floor leader of the ruling People Power Party, speaks during a party meeting at the National Assembly in Seoul, Saturday. Yonhap

Park Chan-un, a law professor at Hanyang University, argued that the impeachment trial is fundamentally a "disciplinary trial" focused on whether Yoon violated the Constitution, and thus withdrawing the insurrection allegations is a logical move.

"The Constitutional Court is not a criminal court; it decides whether to remove Yoon from office. Technically, a ruling to oust him can be made even if the treason charges are not proven. The court will focus on whether he made Constitutional violations in regard to his martial law declaration, and decide whether his actions were serious enough to justify his removal," the professor wrote on Facebook.

Park added that the PPP's objections likely stem from concerns that the proceedings will move forward swiftly if criminal allegations are exempted from review.

Yoon's legal defense team has faced growing criticism for allegedly attempting to delay court proceedings. During the second preparatory hearing, the court pointed out that the defense had not yet submitted documents explaining the rationale behind Yoon's martial law declaration. The lawyers claimed that the case's broad scope was the reason for the delay in providing the necessary documents.