Some 40 opposition lawmakers have written a letter to King Nordom Sihamoni asking the monarch – the constitutional guarantor of judicial independence and citizens’ right – to intervene to release imprisoned opposition lawmaker Um Sam An.

Sam An was arrested this month upon returning from exile in the United States for comments he made on Facebook last year, alleging the government had ceded land to Vietnam by using the “wrong map” to demarcate the eastern border.

The letter cites Article 9 of the Cambodian constitution, which says the King shall assume the role of arbitrator to ensure the faithful execution of public powers.

“Please will His Majesty, the highly respected King, help with a royal intervention to arrange the release of Excellency Um Sam An by royal favor,” the letter reads.

King Norodom Sihamoni’s cabinet chief, Oum Daravuth, said yesterday that he had not yet seen the letter, though said the monarch would respond.

“When it reaches the King, then the King looks and then King will make a decision,” he said.

The government has justified prosecuting Sam An despite his parliamentary immunity by citing the “in flagrante delicto” clause, which allows the arrest of lawmakers if they’re caught committing a crime in the act.

Though Sam An was arrested months after his comments were made, the government has argued the clause applies because the social media post is still live.