The Insurrection Act is a federal law that allows the president to deploy the military and National Guard troops to suppress civil disorder, insurrection or rebellion. It was last used by President George H. W. Bush during the Los Angeles riots after the Rodney King verdict in April 1992.

Gov. Gavin Newsom’s office, in a letter to the Trump administration, called the deployment of troops “unlawful” and a “serious breach of state sovereignty.”