“This latest hasty arrest warrant comes immediately on the back of [Aung] San Suu Kyi’s recent victory in Myanmar, which clearly has Hun Sen running scared. He’s doing exactly what all dictators do…acting out of extreme fear,” Mr. Springer said in an email.

“Cambodians now know that change is possible, and Hun Sen can scramble all he wants to mend a cracking dam, but I don’t think any amount of repair is going to stop the levee from breaking,” he added.

Facing Arrest, Sam Rainsy Promises to Return Today

Cambodia Daily | 16 November 2015

Opposition leader Sam Rainsy is set to be arrested upon arrival at Phnom Penh International Airport late tonight after saying he will return from abroad as scheduled despite orders last week that he be arrested for defaming Foreign Minister Hor Namhong.

A warrant was issued on Friday for the arrest of the CNRP president, who has been abroad since November 7, for a defamation case brought against him in 2008 by Mr. Namhong, which had widely been considered nullified as part of a pardon for Mr. Rainsy in 2013.

Mr. Rainsy has made habitual use of his French passport and home in Paris to escape other seemingly politically-motivated convictions, but he told supporters at a rally in South Korea on Saturday that this time would be different.

“They are coming to catch Sam Rainsy. Is Sam Rainsy scared? No!” Mr. Rainsy shouted with CNRP Vice President Kem Sokha at his side during an event in the port city of Busan, which is home to many of the estimated 30,000 Cambodian migrant workers in South Korea.

“Cambodia is my homeland and my motherland, and I absolutely have to come back in order to save our country,” Mr. Rainsy said. “My plans have not changed. Even if I die, it doesn’t matter, I will die as a Khmer and will not die serving the foreigners.”

CNRP officials said early Sunday that Mr. Rainsy would fly into Siem Reap International Airport at about 11 p.m., but party spokesman Yem Ponhearith said last night that plans had changed and the opposition leader would be flying into the Phnom Penh airport.

“He will arrive at 10 p.m. in Phnom Penh. It’s better to arrive in Phnom Penh than in Siem Reap,” Mr. Ponhearith said.

Mr. Rainsy faces two years in prison for making a speech in April 2008 in which he accused Mr. Namhong of being a chief at the Khmer Rouge’s Boeng Trabek prison camp, which housed intellectuals and diplomats called back to Cambodia by Pol Pot’s regime.

The claims are a point of great sensitivity for Mr. Namhong, who has long denied them. In 2011, he won a defamation case he brought against Mr. Rainsy, who dropped his appeal months before receiving a royal pardon in 2013 for a slew of other convictions.

To the surprise of Mr. Rainsy and the CNRP, the pardon he received did not cover the defamation case, and Mr. Namhong’s lawyer last week wrote to the municipal court requesting that the 2011 decision be enforced.

“This is not involved with politics, we just want the law to be implemented,” Mr. Namhong’s lawyer, Kar Savuth, said Sunday of the request. “This is our right during the five-year [statute of limitations]. We can file a complaint any day we want.”

National Police spokesman Kirth Chantharith said that upon Mr. Rainsy’s arrival in Cambodia, police will execute the arrest warrant.

“We will implement the law,” Lieutenant General Chantharith said. “That is the duty of the police, the police implement the law when the courts order it. So the police have to implement it. It is their duty.”

Asked whether police were concerned about the potential for Mr. Rainsy’s supporters to turn out on the streets to protest the arrest, the spokesman said they could handle the situation.

“The police know how to do their work. We’re also concerned, but when they come to implement it, they know what to do,” Lt. Gen. Chantharith said.

Following news of the arrest warrant, the U.S. State Department said that it was concerned about the “deteriorating political climate in Cambodia in recent weeks.”

Mark Toner, a spokesman for the State Department, noted during a press conference in Washington that the arrest order came in the wake of the beating of two CNRP lawmakers outside the National Assembly late last month.

“The timing of these charges gives the appearance of undue political influence in the judicial process,” he told reporters on Friday.

“More broadly, the pattern of actions against the opposition suggests a return to the harsh political practices and tactics…that the Cambodian people have made clear they no longer want.”

Simon Springer, an academic at the University of Victoria in Canada who has studied political developments in Cambodia over the past decade, said the sudden arrest warrant issued for Mr. Rainsy showed that Prime Minister Hun Sen was starting to panic.

“This latest hasty arrest warrant comes immediately on the back of [Aung] San Suu Kyi’s recent victory in Myanmar, which clearly has Hun Sen running scared. He’s doing exactly what all dictators do…acting out of extreme fear,” Mr. Springer said in an email.

“Cambodians now know that change is possible, and Hun Sen can scramble all he wants to mend a cracking dam, but I don’t think any amount of repair is going to stop the levee from breaking,” he added.

Sophal Ear, the author of “Aid Dependence in Cambodia: How Foreign Assistance Undermines Democracy,” said that if Mr. Rainsy returns tonight it would flip the script on 20 years of Cambodian politics, placing the government in uncharted waters.

“Rainsy is not a risk-taker when it comes to jail time. I don’t think he has ever spent a day in jail in Cambodia, unlike Kem Sokha, Mom Sonando [a popular opposition radio station host], and any number of activists and politicians,” Mr. Ear wrote in an email.

“The authorities are betting on his turning away from Cambodia and heading to France for a self-imposed exile as has been his usual pattern. Otherwise, why would they wait until he was in South Korea to issue an arrest warrant?” he added.

Carl Thayer, a Southeast Asia expert at the Australian Defense Force Academy in Canberra, said that if Mr. Rainsy followed through on his promise to return, it would dramatically raise the stakes with Mr. Hun Sen.

“Hun Sen is playing the long game. There are no easy choices for Sam Rainsy,” Mr. Thayer said in an email. “The king could grant a pardon. But if not, Sam Rainsy stands to lose his parliamentary immunity and…the right to stand for election.”

“If he goes to jail and plays the martyr this could provoke street demonstrations that Hun Sen’s security forces would repress. Going to jail would seriously distract Sam Rainsy from the main game which is winning the next set of elections,” he added.

“Sam Rainsy’s best option is to return to Phnom Penh, fight the charges and mobilize public support for his cause. In other words, a clash between the CPP and CNRP is almost inevitable,” he said.

Mr. Rainsy has repeatedly said since the CNRP’s shock wins at the 2013 national election that his arrest would only cause problems for Mr. Hun Sen. In March 2014, he said he no longer needed his French passport for safety.

“Now my strength is the support of the Cambodian people,” Mr. Rainsy said at the time. “With this strength, and with the overwhelming and growing support of the Cambodian people, I am invincible. I do not need anything else.”