By calling on federal troops to suppress protests in Los Angeles, Donald Trump has shown he is willing to put the country on a war footing — and test the boundaries of executive power — to achieve his goals. 

For the first time in decades, the National Guard was deployed on Sunday against citizens on domestic soil against the wishes of a state’s governor, using a rarely invoked law designed to help the US fight off a foreign invasion. A US president last deployed a state’s National Guard without being asked by its governor in 1965, when Lyndon Johnson sent troops to protect civil rights demonstrators in Selma, Alabama.

The deployment of the National Guard in the second-largest US city, one that is largely liberal, was “clearly done as an authoritarian show of strength”, said Ryan Enos, a professor of government at Harvard University.