Separately, the Constitutional Court began deliberations on whether to formally dismiss Yun as president or reinstate him.
The impeached president largely refused to cooperate with criminal investigation over the declaration on military lighting.
Yoon is set to stand trial alongside his former defense minister and senior military commanders, who are accused of helping him plan and execute an attempt to seize total power.
In an unprecedented televised address on December 3, Yoon said he was invoking martial law to protect the country from “anti-state” forces sympathetic to North Korea.
At the time, the militant leader was embroiled in a budget bill that was beset by a corruption scandal, and several of his cabinet ministers were under investigation.
The military announced that all parliamentary activities were suspended and sought to impose control over the media.
The leader of the opposition Democratic Party, Lee Jae-myung, called on people to protest in the National Assembly and asked his fellow lawmakers to immediately vote to overturn the order.
Less than two hours after Yun’s declaration, the 190 lawmakers in attendance – including some from the president’s party – voted unanimously for him.
Soldiers equipped with rifles were seen entering the parliament building through broken windows as the dramatic confrontation erupted.
Thousands of civilians gathered in front of the meeting and tried to block the soldiers.
Yoon was impeached by parliament and removed from office on December 14.
The case sparked South Korea’s worst political crisis in decades and polarized the country.
Many of his hardliners rallied around him. On Friday, tens of thousands gathered for a protest, demanding his release and return to office.
If Yoon is removed from office, a presidential election will be held within 60 days.
Prosecutors did not immediately respond to requests for comment.
