Trump administration officials said the deployment to Chicago was separate from the operation in Portland, which ostensibly was to protect the federal courthouse there.
But the Homeland Security Investigations agents have broad authority to enforce federal laws in cities, and the Trump administration deployed them this year to so-called sanctuary cities in an enhanced arrest campaign against undocumented immigrants. The administration has also previously deployed federal officials to combat crime in Chicago, including agents from the Bureau of Alcohol, Tobacco, Firearms and Explosives.
The Department of Homeland Security asserted that it was acting within the law, pointing to 40 U.S. Code 1315. Chad F. Wolf, the department’s acting secretary, can deputize officers in any department agency, like ICE, Customs and Border Protection or the Secret Service “as officers and agents for duty in connection with the protection of property owned or occupied by the federal government and persons on the property,” according to the law.
But the federal agents would not be limited to guarding federal property. Under the law, the agents could also conduct investigations of crimes committed against a federal property or federal officer throughout the city.
Carrie Cordero, a senior fellow for the Center for a New American Security, said that the federal statute did provide flexibility to tap members of various agencies to assist in guarding federal property, but that it was never intended to send border agents trained to investigate a drug cartel to crack down on protesters in the streets.
“What’s happening is the administration is using D.H.S. to perform basically a federal policing function, which in my view is unconstitutional and is certainly not what Congress intended when it created the department,” she said.
Stephen I. Vladeck, a law professor at the University of Texas at Austin, said it was not clear how federal agents could occupy the streets of a city that is 99 percent not federal property. “It’s of course the prerogative of the federal government to enforce federal law and protect federal property,” Mr. Vladeck said. “It is not the job of the federal government to be a general police force for all crimes.”