The president’s comments follow his statements Friday when he raised the idea of using the Guard in Chicago, as he previously did in Los Angeles and currently is doing in Washington, D.C.

The intrigue: Former Mayor Rahm Emanuel argued on CNN Sunday that Trump's deployment threat isn't about crime, but about supporting anti-immigration efforts in sanctuary cities. In Chicago, a city ordinance prohibits local police from supporting federal immigration operations.

If Trump sends the National Guard into cities without the consent of governors, state leaders would be able to file court challenges, as California Governor Gavin Newsom did to block Trump from federalizing the National Guard to quell protests and riots over his immigration policy in Los Angeles earlier this summer, Banks said.