Associated Press (AP) — Mayors from four major cities are set to testify Wednesday in Congress as Republicans take aim at “sanctuary cities," arguing that they impede the Trump administration’s mass deportation agenda and protect people who are in the United States illegally.

Mayors Michelle Wu of Boston, Brandon Johnson of Chicago, Mike Johnston of Denver and Eric Adams of New York will appear before the House Committee on Oversight and Government Reform.

In an indication of what's likely to come, the Republican majority last week released a nearly three-minute-long video previewing the hearing. It opens with images of the Constitution catching fire and burning, revealing photos of the four mayors. It goes on to show arrests by Immigration and Customs Enforcement agents of people who'd committed crimes in those cities interspersed with comments from the mayors and news stories showing negative impacts of migration surges.

The video ends with the committee chair, Rep. James Comer of Kentusky, threatening to cut the cities' federal funding if they don't cooperate with immigration enforcement.

There’s no strict definition for sanctuary policies or sanctuary cities, but the terms generally describe limited cooperation with ICE. The agency enforces U.S. immigration laws nationwide but often seeks state and local help to hold people who've been arrested or convicted of a crime until federal officers can take custody.

In communities that don't cooperate, ICE agents go into communities to track down people after their release. ICE argues that this is dangerous and strains resources.

Trump administration officials have also argued that if communities work with them on immigration enforcement, “collateral arrests" — when ICE detains people other than those targeted — are less likely.

“Sanctuary cities want to keep locking us out of jails," President Donald Trump’s border czar, Tom Homan, told reporters. “They force us into the neighborhood to find the bad guys. When we find the bad guy, many times they’re with others.”

But some cities and states say cooperating with ICE means victims and witnesses who are in the U.S. illegally won’t come forward. And, to varying degrees, officials argue that they want their localities to be welcoming places for immigrants.

Advocates say that while ICE claims to target “the worst of the worst” — meaning immigrants who've committed heinous crimes in the U.S. — they end up going far beyond that, destabilizing communities.

Courts have repeatedly upheld the legality of most sanctuary laws.

But the Trump administration continues to target them and has sued Chicago and Illinois as well as New York state over various immigration laws.

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