A Democratic staffer who has worked for several San Francisco elected officials was detained by federal immigration authorities Thursday in Las Vegas, the Department of Homeland Security confirmed.Ho-Yin Mo, a field representative for Assemblymember Catherine Stefani, was arrested during an enforcement operation at Harry Reid International Airport and remained in custody Tuesday. A DHS spokesperson said Mo entered the U.S. in 2020 “on a temporary basis but illegally overstayed his welcome.”Stefani on Tuesday called for Mo’s immediate release and insisted he is a legal employee of her office. The incident has shocked San Francisco’s political community, and friends have mounted an effort to support Mo’s legal defense as he fights deportation to Hong Kong.“My message today is simple: I am respectfully calling for Ho Yin Mo’s release as soon as possible,” Stefani told The Standard. “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.”The Trump administration has aggressively expanded the types of deportation cases pursued by U.S. Immigration and Customs Enforcement, including by targeting those who have legally obtained work and have pending asylum claims. DHS implied, in its statement, that Mo was targeted despite his status landing in a legal gray area.Let’s vote, San Francisco: Introducing The Standard’s 2026 Voter GuideICE frees SF lawmaker's aide on bond. But the deportation fight isn't overMaria Su warns SF teachers not to delete student records as DOJ investigation heats upA DHS spokesperson said, “Work authorization or a pending application do NOT confer legal status in the United States. 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.”Mo was previously an anchor and reporter at KTSF, a Chinese-language TV station based in the Bay Area. He also worked as a field representative for former Mayor London Breed’s 2024 reelection campaign.Stefani praised Mo’s work on behalf of her office, saying he offers a unique form of outreach to Chinese American constituents who recognize him from his work as a TV reporter. Her Assembly district, on the west side of San Francisco, is home to one of the country’s largest electorates of Chinese-speaking voters .Stefani added, “And his work goes far beyond presence. Ho-Yin helps people access affordable healthcare coverage, childcare, and food support. Our whole community eagerly awaits Ho-Yin’s return to his home and his job, where he is loved and adored.”More about the authorDustin Gardiner reports on California and San Francisco politics for The Standard.