City and county officials in Silicon Valley are pursuing moratoriums on new federal immigration detention facilities, aiming to shield the region from President Donald Trump's "mass deportation" agenda.

Federal law supersedes conflicting state and local rules, leaving local officials with limited power to block such projects outright. But San Jose Mayor Matt Mahan said the group is using a new legal strategy to temporarily halt construction of U.S. Immigration and Customs Enforcement detention centers while officials draft laws to address their potential health and environmental effects.

The push comes as ICE seeks to build a detention center on a 26-acre site it purchased near Gilroy, a Silicon Valley suburb. The Trump administration has paused the proposal as state and county officials challenge it in federal district court.

"We have zoning for a reason," said Mahan, a moderate Democrat who mounted an unsuccessful bid for California governor earlier this year. "We should really scrutinize whether it's a permissible use to turn a private farm into a mass deportation center."

Mahan said Santa Clara and San Mateo counties, along with several smaller cities in Silicon Valley's affluent suburbs, are also expected to adopt moratoriums. Rep. Sam Liccardo, who represents the region, announced the effort at a news conference Wednesday.

It's the latest in a series of challenges to Trump's mass detention and deportation agenda, which has faced numerous setbacks in the courts. Cities and counties across the country have also sought to impose rules limiting ICE facilities.

Liccardo, a first-term Democrat closely aligned with the region's powerful tech industry, said the moratoriums are meant to deter ICE from conducting more aggressive operations in Silicon Valley. The region, and the broader San Francisco Bay Area, has seen fewer large-scale ICE sweeps than other liberal-leaning metro areas, such as Minneapolis, Chicago or Boston. Last fall, Trump called off a surge of federal troops planned for San Francisco after a late-night call with the city's mayor, Daniel Lurie, and pleas from major tech CEOs, including Nvidia's Jensen Huang.

"What the public sees on television or social media is certainly horrific: citizens being shot, families being separated, children seeing things children should not have to see," Liccardo said. "Of course, Lord knows what happens inside [detention centers]."

Mahan said he witnessed deplorable conditions when he visited a detention center near the Mexico border earlier this year during his campaign for governor. He said thousands of people were crammed into a facility without any natural daylight and without reliable access to health care.

"You could hear people yelling for help," Mahan said. "It was just an incredibly unsettling experience."

ICE and the Department of Homeland Security did not immediately respond to a request for comment.