Chicago is bracing for the arrival of federal troops after US President Donald Trump threatened to invoke the Insurrection Act of 1807, a law that permits the president to deploy military forces within the country.

Speaking to reporters on Monday, Trump said he would not hesitate to use the powers “if necessary.” “If people were being killed and courts or governors were holding us up, sure, I’d do that. We have to make sure that our cities are safe,” he said.

Trump has authorized the deployment of 300 National Guard troops in Chicago and an additional 200 from Texas, expected to arrive by Wednesday. The administration claims the move is aimed at controlling crime and protecting Immigration and Customs Enforcement (ICE) officers amid growing protests against immigration enforcement.

Protesters have clashed with ICE officers in both Chicago and Portland, prompting Trump’s push for expanded federal intervention. However, a federal judge temporarily blocked the deployment of the National Guard in Portland, citing constitutional concerns.

Illinois Governor JB Pritzker condemned the move, calling it “an authoritarian march,” and vowed to resist. Chicago Mayor Brandon Johnson also signed an executive order declaring certain public spaces as “ICE-free zones,” barring federal agents from using city-owned areas for immigration enforcement.

“We have a rogue, reckless group of heavily armed, masked individuals roaming throughout our city that are not accountable to the people of Chicago,” Johnson said.

Earlier this year, Trump had deployed troops to Los Angeles and Washington, D.C., drawing criticism for using military forces in civilian settings. The potential invocation of the Insurrection Act has raised alarms among civil rights groups and state officials over federal overreach and the erosion of local authority.