Under U.S. law, military units are barred from engaging in domestic law enforcement, although Trump has proposed invoking the Insurrection Act, a sweeping law, that could give him broader powers to direct National Guard units as he sees fit.

“We don't like uniform military in our domestic affairs at all,” says William Banks, professor emeritus of public administration and international affairs. “The default is always have the civilians do it. The cops, the state police, the city police, the sheriffs,” he says.

Using the military for domestic law enforcement would be a fundamental shift, one which Banks argues too few Americans have considered or grappled with. “It would turn our whole society upside down…all these arguments about him being an autocrat or dictator, it is not a stretch,” he says. 

Read more in the ABC News article, “Trump wants a mass deportation program. How much could it cost?”