The country’s anti-corruption agency said it withdrew its investigators after the presidential security service blocked them from entering Yoon’s residence for hours, due to concerns about their safety.

The agency said its outnumbered investigators had several scuffles with presidential security forces and expressed “serious regret about the attitude of the suspect, who did not comply with the legal process.”

It said detaining Yoon would be “virtually impossible” as long as he is protected by the presidential security service.

The agency plans to “strongly demand” that the country’s acting leader, Deputy Prime Minister Choi Sang-mok, instruct the service to comply with their execution of the detainment warrant.

Outside the residence, a large group of pro-Yoon protesters braved freezing temperatures for hours, waving South Korean and American flags while chanting slogans vowing to protect him.

The National Police Agency said it planned to investigate the chief and deputy chiefs of the presidential security service on suspicion of obstructing official duty and summoned them for questioning on Saturday.

Yoon, a former prosecutor, has resisted investigators’ attempts to question him for weeks.

The last time he is known to have left the residence was on December 12, when he went to the nearby presidential office to make a televised statement to the nation, making a defiant statement that he will fight efforts to oust him.

Investigators from the country’s anti-corruption agency are weighing charges of rebellion after Yoon, apparently frustrated that his policies were blocked by an opposition-dominated parliament, declared martial law on December 3 and dispatched troops to surround the National Assembly.

Parliament overturned the declaration within hours in an unanimous vote and impeached Yoon on December 14, accusing him of rebellion, while South Korean anti-corruption authorities and public prosecutors opened separate investigations into the events.

A Seoul court issued a warrant to detain Yoon and a separate warrant to search his residence on Tuesday, but enforcing them is complicated as long as he remains in his official residence.

Yoon’s lawyers, who filed a challenge to the warrant on Thursday, say it cannot be enforced at his residence due to a law that protects locations potentially linked to military secrets from search without the consent of the person in charge.

The office said it will discuss further actions but did not immediately say whether it would make another attempt to detain Yoon. The warrant for his detention is valid for one week.

Yoon’s lawyers have also argued that the Corruption Investigation Office for High-ranking Officials, which is leading a joint investigation with police and military investigators, lacks the authority to investigate rebellion charges. They said that police officers don’t have the legal authority to assist in detaining Yoon, and could face arrest by either the “presidential security service or any citizens.” They didn’t elaborate further on the claim.

If investigators manage to detain Yoon, they will likely ask a court for permission to make a formal arrest. Otherwise, he will be released after 48 hours.

During a background briefing to reporters, an official from the anti-corruption agency said its investigators were able to approach within 200 metres of Yoon’s residence but were stopped by a barricade comprising around 10 vehicles and approximately 200 members of the presidential security forces and troops.

The official, who spoke on condition of anonymity per department rules, said three of its prosecutors were eventually allowed to approach the building but they weren’t able to confirm whether Yoon was inside.

While the presidential security act mandates protection for Yoon, it does not authorise the presidential security service to block court-ordered detainments, which would amount to an infringement on judicial authority, said Park Seong-bae, an attorney specialising in criminal law.

While the president mostly has immunity from prosecution while in office, the protection does not extend to allegations of rebellion or treason.

“There’s a high possibility that the act of blocking the execution of a detainment warrant would constitute an obstruction of official duty,” he said.

The law requiring consent of the person in charge for searches in locations with potential military secrets could continue to hinder Yoon’s detainment.

Courts often require law enforcement officials to obtain search warrants with detainment warrants in case they need to search the site to locate the suspect, which is also what the anti-corruption agency did in their pursuit of Yoon.

It’s unlikely that the approval could come from the country’s acting leader, Choi, as it would be difficult to see him as the person in charge of Yoon’s residence, Park said.

Park Chan-dae, floor leader of the liberal opposition Democratic Party, called the anti-corruption agency’s withdrawal regrettable and urged the agency to make another attempt to detain Yoon on Friday.

Kwon Young-se, who heads the emergency leadership committee of Yoon’s conservative People Power Party, called the agency’s effort to detain Yoon “highly unfair and exceedingly improper,” saying that there is no risk of Yoon attempting to flee or to destroy evidence.

Thousands of police officers gathered at Yoon’s residence on Friday, forming a perimeter around a growing group of pro-Yoon protesters who braved freezing temperatures for hours, waving South Korean and American flags while chanting slogans vowing to protect him. There were no immediate reports of major clashes outside the residence.

Yoon’s defence minister, police chief and several top military commanders have already been arrested over their roles in the period of martial law.

Yoon’s presidential powers have been suspended since the National Assembly voted to impeach him on December 14.

Yoon’s fate now lies with the Constitutional Court, which has begun deliberations on whether to uphold the impeachment and formally remove Yoon from office or reinstate him.

At least six justices on the nine-member Constitutional Court must vote in favour to remove him from office.

The National Assembly voted last week to impeach Prime Minister Han Duck-soo, who became acting president after Yoon’s powers were suspended, over his reluctance to fill three Constitutional Court vacancies ahead of the court’s review of Yoon’s case.

Facing growing pressure, the new acting president, Choi, appointed two new justices on Tuesday, which could increase the chances of the court upholding Yoon’s impeachment.