If President Trump deploys troops to other American cities, experts say it would be a clear departure from founding principles and invite a legal challenge.

A federal judge is hearing arguments on whether military troops deployed this summer by the Trump administration to Los Angeles violated a federal law that bars troops from conducting law enforcement duties within the country.

Attorneys for Gov. Gavin Newsom headed back to court Monday over President Donald Trump ’s use of the California National Guard to subdue protests in Los Angeles, a tactic the White House is now repeating in the nation’s capital in what’s it’s calling a crime crackdown.