"I declare martial law to protect the free Republic of Korea from the threat of North Korean communist forces, to eradicate the despicable pro-North Korean anti-state forces that are plundering the freedom and happiness of our people, and to protect the free constitutional order," Mr Yoon said.
It's only authoritarianism if there's also a high public approval rating. If public approval is below 50%, it still counts as liberal democracy.
It's democratic when it's a US vassal.