By the time Nith* arrived in Wisconsin at the age of 5, he had escaped a genocide and lived in refugee camps in two different countries.

Over the next 40 years, he built a new life, earning a bachelor’s degree, opening a printer repair business, and raising two children. “I called America home,” Nith said. “I never thought about needing to become a citizen. I felt like I was a part of America. I never thought I would get in trouble.”

Then, in 2014, he was arrested and convicted of marijuana possession. Last year, US immigration officials came knocking at his door.

Nith, who asked to be referred to by a pseudonym out of concern that his status as a deportee could affect his job prospects, is among 43 Cambodian citizens who arrived on Thursday in the single largest group of US deportees to ever to be sent to Cambodia.

Bill Herod, spokesman for the Khmer Vulnerability Aid Organization, said the mood was “very positive” despite the uncertain futures many of them face.

“They’re very happy to be out of shackles and off the plane,” Herod said.

The repatriation program sparked a rift between the US and Cambodia last year after Cambodia stopped issuing travel documents to would-be deportees, leading the US to impose visa sanctions for top Cambodian foreign affairs officials.

Immigration advocates have criticised the program as inhumane. On Tuesday, Asian Law Caucus attorney Anoop Prasad, who was representing many of Thursday’s arrivals in a class action lawsuit, tweeted that he was “heartbroken”.

“Minutes ago the largest ever deportation flight to Cambodia took off,” Prasad wrote. “All are refugees of the Khmer Rouge . . . Taking a moment to grieve before continuing to fight.”

US Department of Homeland Security spokesman Brendan Raedy did not directly respond to questions about why the number of arrivals Thursday was lower than expected, or allegations that some of them had physical and mental disabilities.

In a statement, Raedy said each deportee was deemed “fit to travel” and added that visa sanctions remain in effect.

Foreign Affairs spokesman Chum Sounry expressed hope the sanctions would be lifted now that the government has “back[ed] our affirmation by concrete act”.

As for Nith, he’s made contact with a cousin who lives in Phnom Penh and hopes to restart his printer repair business in Cambodia, with his wife and daughter by his side. “It’s scary,” Nith said. “But I’m trying to stay positive.”