Kem Sokha was released from a Tbong Khmum prison in September 2018, a year after he was arrested in a midnight raid in 2017 for allegedly conspiring with foreign powers.
The blockade in Poipet comes as CNRP leaders have faced difficulties reaching Thailand.
If Rainsy did not return to Cambodia on November 9, it certainly would deal a heavy blow to the morale of CNRP supporters, said Astrid Norén-Nilsson, author of Cambodia's Second Kingdom: Nation, Imagination, and Democracy.
Cambodia also urged the international community not to interfere in its internal affairs and respect its sovereignty.
The CPP won all 125 seats in the National Assembly in July after it oversaw the banning of the country’s main opposition party, the Cambodia National Rescue Party.
The NEC said that it would also remove those who had been reported deceased in the same period and an additional 100,000 names.
The Supreme Council of Consultations (SCC), as the forum will be known, will provide a check on the power of the ruling Cambodian People’s Party, according to Hun Sen.
Kem Sokha was not present at the hearing, which lasted for nearly one hour.
Opposition Cambodia National Rescue Party was dissolved by court last year for alleged complicity in treason plot.
Results ensure Prime Minister Hun Sen's tightfisted three-decade grip on power.
Restrictions apply to those 'responsible for the most notable anti-democratic actions taken in the run-up to the flawed July 29 election'.
Prime Minister Hun Sen, who has ruled Cambodia for over 33 years, remains defiant.
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