Under the order, private businesses can choose to display signage indicating that ICE cannot enter without a warrant—thereby designating “their property as part of a city-wide network of community spaces that stand together in affirming the safety, dignity, and belonging of all of our residents,” the mayor said.
Johnson touted the order for building “a broad civic shield that limits the reach of harmful enforcement practices. It strengthens neighborhood solidarity and it reaffirms Chicago’s role as a welcoming city.”
Okay, I think part of the pushback you’re getting is due to you being just flat wrong about how local / state / federal law enforcement interaction works - a state municipality can absolutely arrest federal LEOs. It happens, not with frequency but it is not unknown by any means.
This situation is largely unprecedented in the political landscape but legally it’s completely feasible for the Chicago mayor to do what’s being proposed, and while I do doubt CPD would choose not to be their usual bastard selves, in a great deal of recent reporting they do appear to be siding with the city over ICE (or at least, not siding with ICE over the city. Which is shockingly egalitarian by their standards, really).