Nai Nep and Thim Thos, a 49-year-old commune official for the party, were questioned for two hours on Tuesday.
Professor John Greenman began offering such trips in 2010.
Citizens have the right to participate in politics, economics, society, culture—including peaceful protests, Lao Monghay said.
Son Chhay is drafting a bill to provide freedom of information that he hopes to put before the National Assembly soon.
In an e-mail interview, Royce said he has sent a letter to Secretary of State noting his concern for an ongoing culture of impunity.
Cambodia has around 200 government-provided land concessions, totally 2 million hectares.
The men had been forced to work long hours for little pay aboard the boat before escaping to Indonesia.
Prime Minister Hun Sen announced last week he wanted the men arrested.
Some of Wednesday’s female protesters tore off their shirts as they faced off with riot police carrying batons and shields.
Hun Sen said Tuesday he would take back land concessions if the violence continues.
Nearly 80 land cases involved government land concessions that affected more than 30,000 families.
Sia Phearum told “Hello VOA” people are being forced off land they earned through “backbreaking” work.