hundreds of Marines moved into Los Angeles and began guarding federal property and personnel a week after demonstrations erupted downtown.

To some Angelenos, the notion that their city was being invaded by Mexico might sound like a fantastical twist on the history of U.S.-Mexico military relations.

"I urge the authorities to respect the right to peaceful assembly and to uphold human rights in law enforcement, including by refraining from any resort to military force when civilian authorities ar...