What next? South Korea's President Yoon ousted as court upholds impeachment

South Korean President Yoon Suk Yeol was ousted by the Constitutional Court on Friday, which upheld parliament's impeachment motion over his imposition of martial law last year that sparked the country's worst political crisis in decades.

The ruling caps months of political turmoil that have overshadowed efforts to deal with the new administration of U.S. President Donald Trump at a time of slowing growth in Asia's fourth-largest economy.

With Yoon's ouster, a presidential election is required to take place within 60 days, according to the country's constitution.

Prime Minister Han Duck-soo will continue to serve as acting president until the new president is inaugurated.

"The Constitutional Court’s unanimous ruling has removed a major source of uncertainty," Professor Leif-Eric Easley of Ewha University in Seoul. "And not a moment too soon, given how the next administration in Seoul must navigate North Korea’s military threats, China’s diplomatic pressure, and Trump’s trade tariffs."

Acting Chief Justice Moon Hyung-bae said Yoon violated his duty as president with his December 3 martial law declaration, acting beyond the powers given to him under the constitution and describing his actions as "a serious challenge to democracy".

"(Yoon) committed a grave betrayal of the people's trust who are the sovereign members of the democratic republic," Moon said, adding that Yoon's declaration of martial law created chaos in all areas of society, the economy, foreign policy.

Thousands of people at a rally calling for Yoon's ouster, including hundreds who had camped out overnight, erupted into wild cheers on hearing the ruling, chanting "We won!"

Supporters of Yoon who were gathered near his official residence reacted in anger. One protester was arrested for smashing a police bus window, the Yonhap news agency reported.

The South Korean won was largely unfazed by Friday's ruling, remaining at about 1% higher vs dollar at 1,436.6 per dollar by 0249 GMT. The benchmark KOSPI was down 0.7%, also unchanged from the morning as the expected scenario was for the court to uphold the impeachment bill.

ARGUMENTS REJECTED

The court rejected most of Yoon's argument that he declared martial law to sound the alarm over the main opposition party's abuse of its parliamentary majority, saying there were legally justified avenues to address disagreements.

The martial law decree lacked justification and was also procedurally defective, Moon said. Mobilising the military against parliament to disrupt its functions was a grave violation of Yoon's constitutional duty to safeguard the independence of the three branches of government, he added.

Yoon's ruling People Power Party's interim leader Kwon Young-se apologised to the people saying the party humbly accepted the court's ruling and pledged to work with the acting president to stabilise the country.

Acting President Han Duck-soo, speaking after the ruling, said he would do all he could to ensure an orderly and peaceful presidential election.

Finance Minister Choi Sang-mok is expected to convene an emergency meeting with the Bank of Korea governor and financial regulators.

The 64-year-old Yoon faces a criminal trial on insurrection charges related to the martial law declaration. The embattled leader became the first sitting South Korean president to be arrested on January 15 but was released in March after a court cancelled his arrest warrant.

The crisis was triggered by Yoon's declaration of martial law, which he has said was needed to root out "anti-state" elements and the opposition Democratic Party's alleged abuse of its parliamentary majority that he said was destroying the country.

Yoon lifted the decree six hours later after parliamentary staffers used barricades and fire extinguishers to ward off special operations soldiers who arrived by helicopter and broke windows as they sought to enter parliament, where lawmakers voted to reject martial law. Yoon has said he never intended to fully impose emergency military rule and tried to downplay the fallout, saying nobody was hurt.

WHAT HAPPENS NEXT?

South Korea will have to hold a fresh presidential election within 60 days. Until then, Prime Minister Han Duck-soo will remain as acting president.

The new president will take office as soon as the National Election Commission declares the results.

After South Korea's last impeachment and removal, in 2017, a presidential election was held on May 9 following the Constitutional Court's decision to remove then-President Park Geun-hye on March 9.

Park's successor was inaugurated the day after that vote.

Polls show opposition leader Lee Jae-myung, who narrowly lost to Yoon in the 2022 presidential election, is maintaining his lead for the snap election, leaving no major challengers.

A populist outsider and former governor of the most populous province in South Korea, Lee has, however been beset by his own legal troubles and scandals that could bar him from an election run. He faces trials in cases from bribery to charges related to a property development scandal.

WHAT WILL BE THE NEW LEADER'S PRIORITIES?

Whoever wins the election, the priority will be to bring stability to domestic politics and take on the daunting task of dealing with U.S. President Donald Trump.

Trump has been pressuring allies with tariffs and demanding that South Korea pay more for American troops stationed there.

Tension on the Korean peninsula is also running high. Yoon took a hard line against North Korea, amid Pyongyang's advances in military and space capabilities and warming ties with Russia.

South Korea suspended a military pact with the North meant to reduce military tension by curbing live-fire exercises along the border. The North's constitution has designated South Korea as the principal enemy.

WHAT NEXT FOR YOON?

In separate criminal proceedings, Yoon was indicted in January on charges of insurrection, punishable by life imprisonment or even death, although South Korea has not executed anyone in decades.

A defiant Yoon has denied he masterminded an insurrection.

Yoon, a former prosecutor, used to put people in jail. But, he became the first incumbent South Korean leader to be arrested in January, after initially defying efforts to question him in the criminal case.

He has now been freed from detention after a court quashed his arrest warrant while he stands trial.

WILL HIS REMOVAL END THE CRISIS?

Yoon's removal from office was the culmination of months of turmoil in which hundreds of thousands of South Koreans took to the streets, week after week, either to protest or support him.

The upheaval has further exposed deep social rifts between conservatives and liberals and stepped up pressure on institutions and the military, which had found itself in a quandary over whether to enforce martial law.

Political dysfunction marked the run-up to Yoon's martial law declaration, with the opposition-led parliament blocking much of his agenda and impeaching a string of officials.

It remains unclear whether Yoon's fired-up supporters will now accept the court's ruling or continue their street protests.