The regulation, signed by Prime Minister Hun Sen May 31, calls on authorities to make lists of squatter communities.
Ung Rithea is currently in jail and awaiting trial of fraud charges related to the case.
Mu Sochua told VOA Khmer she has no intention of paying the fine.
Sam Rainsy is currently on a visit to the US to build political support for his party, which holds 26 seats in the National Assembly.
The ILO estimated in 2007 an influx of 270,000 Cambodian job seekers entering the market each year.
The letters now appear to be part of a business dispute with four other foreign men, who were found to be no threat.
Mu Sochua said she would not pay the fine.
Two men were accused of incitement in an ongoing land dispute between villagers and a powerful ruling party senator.
It’s rare for a company to gain a land concession from the government and not have a conflict with the locals.
All three companies are owned by Ly Yong Phat, a powerful senator for the ruling Cambodian People’s Party.
In Cambodia scores of men have recounted stories of modern-day slavery on board Thai and Malaysian fishing vessels.
The delegation included three Khmer monks who had spent about one year in jail each in Vietnam.