The first parliamentary vote to impeach Yoon was held on December 7, but failed after the ruling party boycotted the vote.
On December 3, Yoon declared martial law, claiming that the opposition was sympathizing with North Korea and plotting subversion. The parliament defied the presidential declaration and voted to lift the martial law.
The office of the speaker of the parliament, Woo Won-shik, said that the president's declaration of martial law was invalid following the lawmakers' vote.
Shortly after, Yoon lifted martial law and apologized to the nation. He was banned from leaving the country pending the results of an investigation, while former Defense Minister Kim Yong-hyun was arrested on suspicion of treason.