President Yoon Suk Yeol declared a state of martial law late Tuesday night. However, it could be short-lived if the National Assembly, controlled by the opposition party, votes to revoke it.

As soon as Yoon made the surprise move, the main opposition Democratic Party of Korea swiftly mobilized to repeal the measure, although early reports said access to the National Assembly building was physically blocked under the emergency decree.

Chairman Lee Jae-myung of the Democratic Party issued an emergency directive to all members to convene at the National Assembly’s voting chamber. Despite access restrictions imposed under the decree, the lawmakers began gathering to initiate efforts to annul the declaration.

It was not immediately clear how many entered the building, as of 11:54 p.m.

Under Korean law, if the Assembly demands the lifting of martial law with the consent of a majority of its members, the president must lift it.

The Democratic Party alone holds 170 out of 300 seats in the country’s unicameral parliament.

By law, the parliament can convene a voting session via video conference, in case of natural disasters and other circumstances.

Yoon invoked Article 77 of the Constitution late Tuesday, declaring martial law to address what he described as a dire threat to national security posed by “treacherous pro-North anti-state forces.” Announcing the measure, Yoon vowed to protect the nation’s Constitutional order and eradicate subversive elements.

“To safeguard the Republic of Korea from the threats posed by North Korean communist forces and protect our citizens' freedom and happiness from subversive anti-state elements, I hereby declare martial law,” Yoon stated.

The emergency measure grants the president sweeping powers to limit civil liberties such as freedom of speech, press and assembly, as well as to override judicial and governmental authorities. The Constitution mandates that the National Assembly be notified immediately of martial law, and the legislature retains the power to revoke it with a majority vote.