Interior Minister Sar Kheng announced yesterday that he would introduce an amendment to the Constitution banning individuals from doing “anything to impact the national interests” of Cambodia, singling out ex-opposition figure Kem Monovithya as an example.

“Each individual Cambodian must not do anything to impact the national interests of the Kingdom of Cambodia both domestically and abroad,” Kheng said, speaking at an annual review of the Ministry of Land Management in place of Prime Minister Hun Sen.

He went on to add that this point “must be in the Constitution”.

Kheng, who has been appointed to the head of a 12- man working group tasked with introducing constitutional amendments, said he had seven amendments in mind, but only shared three. One, announced on Wednesday, would remove secretaries and undersecretaries of state’s designation as cabinet members. Another was only vaguely referenced yesterday as addressing foreign “interference”.

In Kheng’s speech, he said the amendment covering “national interests” could relate to opposition leader Kem Sokha’s daughter, Kem Monovithya, who Kheng said “compared Cambodia with Afghanistan, Iraq, Syria, Libya, Egypt and other countries”.

Sokha was arrested in September on widely decried charges of “treason” for telling supporters he received political advice from the United States. His Cambodia National Rescue Party – the nation’s only viable opposition – was dissolved shortly thereafter over accusations it was fomenting foreign-backed “revolution”. Monovithya, who was also a prominent party official, has frequently appealed to the international community for sanctions and other measures to pressure the government to restore true multiparty democracy.

“She suggested that the United Nations suspend Cambodia’s seat at the UN. How can she do that?” Kheng asked, adding that the UN allowed the Khmer Rouge to keep its seat, despite the group having killed almost 2 million people.

Kheng also blasted Monovithya for seeking sanctions against Cambodia.

“Who is going to be affected by the economic sanctions, the cutting down of quotas? Whose interests are affected? Does it affect the individual Samdech Hun Sen or ... the whole population?”

“She holds awful ideas,” Kheng added.

Monovithya yesterday accused the government of “openly targeting” her in recent weeks.

“Despite these threats and risks, I along with millions of Cambodians who want positive change, have no choice but to push back at this authoritarian regime,” she said.

Independent legal analyst Sok Sam Oeun said Kheng’s proposed prohibition would be both vague and abnormal. “What does it mean to harm the nation?” he asked. “Asking the EU or UN to punish anyone who abuses human rights – that does not mean you harm the nation.”

Sam Oeun added that such a law would be unacceptably vague for an “independent judiciary”, but said it would likely be acceptable to Cambodia’s courts, which are widely seen as an extension of the executive government.

Chak Sopheap, director of the Cambodian Center for Human Rights, said any amendment should “respect the fundamental principles upon which Cambodia is based”.

“No amendment can contravene freedom of expression, which is protected by the Constitution itself,” she said. “Any amendment or addition should be carefully drafted, each key term must be strictly defined, each constitutive element clearly listed, in order to respect legal certainty and leave no space for an arbitrary interpretation.”

Both Sopheap and San Chey, of the Affiliated Network for Social Accountability in Cambodia, said any amendment should receive consultation from civil society before being passed. “Some cunning laws have been used, and they affected human rights and democracy,” Chey said.

At yesterday’s meeting, Kheng also claimed that on a visit earlier this month W Patrick Murphy, a US State Department deputy secretary of state, had asked that the US not be brought up during Sokha’s upcoming treason trial. Kheng said that would be “difficult” to avoid.

The Cambodian government has frequently accused the US – along with the EU – of backing the CNRP’s purported plot to topple the government. “It is difficult because Kem Sokha admitted it,” he said, referring to a 2013 video in which Sokha speaks about getting help with his political platform from American advisers.

The US Embassy in Phnom Penh did not respond to requests for comment.