Cambodia's government has targeted about 50 people in its most concerted legal offensive against its political opponents since 2017, according to copies of court summonses seen Friday. They all were charged with treason for taking part in nonviolent anti-government activities over the past three years.

One of the best known of the group is Theary Seng, a Cambodian-American lawyer who has long been one of the most outspoken critics of Prime Minister Hun Sen and his government. According to a summons she posted Friday on her Facebook page, she is to appear at the Phnom Penh Municipal Court on Nov. 26 to stand trial for conspiracy to commit treason and incitement to commit a felony. If convicted, she could face up to 12 years in prison.

The others face the same charges and also have court dates in late November. Several are believed to reside outside Cambodia. A court spokesman was not able to confirm the total number on Friday, but Am Sam Ath, who works with the Cambodian human rights group Licadho, said there were a total of 56 defendants on two lists of summoned people.

Theary Seng has accused Hun Sen’s government of abusing human rights and being undemocratic. Hun Sen has been in power for 35 years and has often been accused of heading an authoritarian regime. Several Western nations have imposed sanctions on his government, mainly after concluding that Cambodia’s 2018 general election was neither free nor fair. The harshest measure came from the European Union, which this year withdrew some preferential trading privileges.

In 2017, Hun Sen upended the country’s politics with a wide-ranging crackdown on his opponents. Virtually all critical media outlets were forced to close or tone down their coverage, and the sole credible opposition political party, the Cambodia National Rescue Party, was forced by the high court to disband and its lawmakers were removed from Parliament. Many people believe the court acted to ensure that Hun Sen’s Cambodian People’s Party won the 2018 general election, which it did by sweeping all the seats.

Thaeary Seng is currently residing in the United States, but said in an email to The Associated Press that she intends to fly back to Cambodia for her court date.

“Without a doubt, I am determined to appear, I WILL APPEAR in person in court on Thursday, 26 November 2020. I will appear and represent myself for the court hearing,” she wrote.

She described the charges against her as ” trumped-up by this Hun Sen regime in its attempt to intimidate and silence me. They would be laughable if not for the prison term that could, and most likely would, see me languishing inside Cambodia’s notorious prisons for decades.”