Both the paper and the publisher argue that this really has nothing to do with taxes and more to do with Hun Sen trying to curb dissent ahead of the general elections next year.
Kem Sokha, 64, has led the main opposition CNRP since his predecessor, Sam Raimsy, resigned in February after party law amendments outlawed political parties led by people with criminal convictions.
Speaking to 4,000 Cambodian garment factory workers Sunday, Hun Sen claimed Kem Sokha had colluded with the United States against his government and warned the opposition party it could be dissolved if it defended him.
Mr. Kem Sokha's arrest was quickly condemned by opposition leaders and global human rights activists.
The Cambodian Government described the above act as treason and espionage and said the court will handle this case according to the country's regulations.
Fresh News frequently runs leaks from inside the government that often precede an investigation or arrest.
"Kem Sokha is in police custody at city hall".
Sokha, President of the Cambodia National Rescue Party (CNRP), was arrested early on Sunday at his home in Phnom Penh and sent to a prison in Tboung Khmum province, about 150 km from here.
Kem Sokha's daughter, Monovithya Kem, also a party official, said on Twitter that her father had been taken away handcuffed after a raid by between 100 and 200 police, who had arrived without an arrest warrant.
During the speech he boasted that the U.S. was "advising me about strategies to change the dictatorship in Cambodia". "For months, we have been witnessing the escalation of government attempts to cripple the opposition, but it appears now that Prime Minister Hun Sen is so afraid of what might happen in a genuine vote, he won't allow for competition at all".
In recent weeks, Mr. Hun Sen's government has cracked down on independent news outlets and democracy advocates.
Washington has a complex and fraught history with Cambodia, secretly bombing it during the Vietnam War era and then becoming one the country's biggest aid donors as it tried to rebuild from the murderous Khmer Rouge years. It accuses the paper of failing to pay taxes.
Last month, the government ordered the US -funded National Democratic Institute to close and has also gone after Cambodian radio stations.
Eighteen radio stations were also ordered off the air last month and local radio stations have been stopped from leasing time to the United States-funded Radio Free Asia and Voice of America.
Among the media in the firing line is the well respected Cambodia Daily, which often criticises the government.
It says the hefty bill was invented by the government and not based on an audit of its books.