Separately, the Constitutional Court has begun deliberations on whether to formally remove Yoon as president or reinstate him.
The impeached president has largely refused to cooperate with a criminal investigation into the declaration of martial law.
Yun is set to go on trial along with his former defense minister and top military commanders, who are accused of helping to plan and execute the full power grab.
In an unprecedented televised announcement on December 3, Yun said he was calling for martial law to protect the country from “anti-state” forces that sympathize with North Korea.
At the time, the embattled leader was deadlocked on a budget bill, embroiled in corruption scandals and several of his cabinet ministers were under investigation.
The military announced the suspension of all parliamentary activities and attempted to impose control over media outlets.
Opposition Democratic Party leader Lee Jae-myung called on people to protest in the National Assembly and asked his fellow lawmakers to immediately vote to repeal the order.
Less than two hours after Yun’s announcement, the 190 lawmakers who had gathered — including some from the president’s party — voted unanimously to block it.
Soldiers armed with rifles were seen entering the parliament building through broken windows as the dramatic confrontation took place.
Thousands of citizens gathered in front of the assembly and tried to stop the soldiers.
Yun was impeached by parliament and suspended from office on 14 December.
The case has sparked South Korea’s worst political crisis in decades and polarized the country.
Many of his die-hard supporters have rallied around him. On Friday, tens of thousands of people gathered to protest, demanding his release and return to office.
If Yun is removed from office, a presidential election will be held within 60 days.
The prosecutor’s office did not immediately respond to requests for comment.
