When troops are overseas, how they can respond to threats is outlined by the rules of engagement. At home, they are guided by standing rules for the use of force, which have to be set and agreed to by Northern Command, and then each Marine should receive a card explaining what they can and cannot do, another U.S. official said.

The U.S. military is set to temporarily deploy about 700 Marines to Los Angeles while additional National Guard troops arrive in the city, a U.S. official told Reuters on Monday. About 300 California National Guard troops were deployed to the streets of Los Angeles on Sunday to help quell a third day of protests over President Donald Trump's immigration enforcement,

The Marines will join National Guard troops deployed to quell clashes between demonstrators and law enforcement after a series of immigration raids in the city.