When can the President of the United States deploy armed forces on US soil?

• Protests in Los Angeles, California, have sparked a nationwide military deployment by President Donald Trump.

• The Posse Comitatus Act (1878) prohibits military troops from civilian law enforcement, unless explicitly authorized by the Constitution or an Act of Congress.

• The Insurrection Act allows the President to deploy the military during civil unrest, either at a State’s request or unilaterally to enforce federal law, suppress rebellion, or protect civil rights.

• The national guard’s federalised role expanded during the Civil Rights era, during protests for school desegregation and the 1965 Selma-Montgomery March.

• The deployment of the national guard to support law enforcement against protests began in 1967.

• The Insurrection Act’s substantive powers, including the procedural mechanism and the deployment of the national guard, are invoked to justify deployment.

• Trump’s memorandum cites Section 12406 of Title 10 of the U.S. Code, which allows the President to call national guard members into ‘federal service’ under certain circumstances, including rebellion against federal authority.

• The deployment of the national guard in California was criticized as an “unlawful” overreach by California Attorney General Rob Bonta and Governor Gavin Newsom.

• In India, Article 355 of the Constitution allows the Union to deploy the army even without a State’s request.