A fight between President Donald Trump and Democratic Gov. Gavin Newsom over the National Guard's presence in California will come to a head in a three-day trial.

Lawyers for President Donald Trump and California Gov. Gavin Newsom are set to face off Monday to determine whether the president violated a 147-year-old law when he deployed the National Guard to quell anti-immigration enforcement protests in Los Angeles – against the wishes of the governor.

Federal immigration officials detained at least one person outside of Gov. Gavin Newsom’s (D) speech on Thursday discussing Texas’s push to redistrict its congressional map, according to local news. Newsom’s office posted images of ICE agents outside the event and wrote,

Nearly two months after President Trump took the extraordinary step of deploying the National Guard to Los Angeles to quell public unrest over immigration raids, the Pentagon on Wednesday announced that it was withdrawing more than a thousand troops.

The National Guard is a reserve force of the U.S. military that is typically deployed by states in response to natural disasters, although it has been used in the past by presidents to help quell domestic unrest - including President George H.W. Bush during the Los Angeles riots in 1992.