But federal officials say his authorized stay expired months later.
DHS says Mo was supposed to leave the country by May 15, 2020, but remained in the United States.
That alleged overstay eventually caught up with him in Nevada.
DHS Says Trump Administration Changed the Rules at Airports
The arrest comes amid expanded immigration enforcement at airports under President Donald Trump.
DHS specifically tied Mo’s detention to the administration’s decision to reverse what the agency described as a Biden-era approach toward domestic air travel by people without lawful immigration status.
The department said:
“DHS reversed the horrendous Biden-era policy that allowed aliens in our country illegally to jet around our country. Under President Trump, DHS will no longer tolerate this. This administration is working diligently to ensure that aliens in our country illegally can no longer fly unless it is out of our country to self-deport.”
DHS has also emphasized an important distinction in Mo’s case: permission to work in the United States is not necessarily the same thing as possessing lawful immigration status.
“All illegal aliens receive due process through immigration proceedings. To be clear: a pending application or work authorization does NOT confer legal status in the United States,” the agency said.
Mo is being held at an immigration detention facility in Pahrump, Nevada, as his case moves through the immigration system.
First Assistant U.S. Attorney Bill Essayli responded to news of the detention with a pointed message.
“No one is above the law, not even the California legislature and its staff,” Essayli said.
From Bay Area Television to Democratic Politics
Mo was hardly an unknown figure in San Francisco.
Before entering politics, the Hong Kong native worked as a television journalist for KTSF, the Bay Area’s Chinese-language television station.
He later moved into Democratic politics, working on former San Francisco Mayor London Breed’s 2024 reelection campaign before joining Stefani’s legislative staff in January 2025.
His work for Stefani put him directly in contact with constituents in San Francisco and the surrounding Bay Area.
That background made his arrest particularly striking.
A former television personality who had become a representative for an elected California Democrat was suddenly sitting in federal immigration custody after passing through an airport.
Stefani quickly came to her employee’s defense.
“Ho Yin is a selfless public servant and a valued, legal employee of the California State Legislature serving our San Francisco and Bay Area communities,” she said.
Stefani also praised Mo’s connection with Chinese-American residents who remembered him from television.
“When Ho Yin and I meet our Chinese-American constituents, he brings a unique sense of belonging to so many who watched him as a TV reporter. And his work goes far beyond presence. Ho Yin helps people access affordable health care coverage, child care, and food support.”
She has called for his release.
“My message today is simple: I am respectfully calling for Ho Yin Mo’s release as soon as possible,” Stefani said.
A Legal Employee — But DHS Says That Is Not the Same as Legal Status
The wording of Stefani’s defense is significant.
She described Mo as a “valued, legal employee” of the Legislature.
DHS, meanwhile, says work authorization does not by itself establish lawful immigration status.
Those two statements are not necessarily contradictory.
Someone may have authorization to work while facing a separate immigration-status issue, depending on the circumstances of the individual case.
Federal officials maintain that Mo overstayed the period of admission granted when he entered the country in 2020.
Mo will have the opportunity to contest the government’s position through immigration proceedings.
Arrest Puts Trump’s Airport Enforcement Strategy in the Spotlight
The broader political significance of the case goes beyond one California legislative employee.
The Trump administration has made immigration enforcement a central priority, and airports provide federal authorities with an obvious enforcement point because travelers must identify themselves before boarding commercial aircraft.
DHS is presenting Mo’s arrest as an example of what changed after Trump returned to office.
For Stefani, the situation creates an uncomfortable collision between California Democratic politics and the administration’s immigration crackdown.
Her office emphasizes Mo’s public service, his work authorization and the assistance he has provided constituents.
The federal government emphasizes something entirely different: DHS says he was required to leave the United States in May 2020 and did not.
Now that dispute will be handled through the immigration process rather than the California Legislature.
And for the Trump administration, the message surrounding the arrest has been unmistakable.
A résumé, a government job and a work permit do not, according to DHS, erase an alleged immigration violation.
As Essayli put it:
“No one is above the law, not even the California legislature and its staff.”
