Yoon was suspended from presidential powers after being impeached by parliament earlier this month over his decision to briefly impose martial law.
Masked martial law troops equipped with rifles, body armour and night-vision equipment entered the parliament where they faced off with staffers who opposed them with fire extinguishers.
The decree lasted just hours until the parliament voted it down and Yoon backed down.
The move shocked the nation, which has been a democracy since the 1980s, caused international alarm amongst allies like the United States and trading partners with Asia’s fourth largest economy.
A Constitutional Court trial is ongoing into whether to reinstate Yoon or remove him permanently from office. It has 180 days to reach a decision.
On Friday, the court held its first preparatory hearing where a request by Yoon’s lawyers for a postponement in proceedings to better prepare was denied. The court said it would move swiftly.
The next hearing is due on Jan 3.
