The Posse Comitatus Act, a 19th-century law that prohibits the use of the military in civilian law enforcement, was at the centre of a landmark ruling on Tuesday as a federal judge struck down Donald Trump's deployment of National Guard troops and Marines in Los Angeles.
Judge Charles Breyer of the Northern District of California said the operation crossed a constitutional line, reigniting debate over the scope of presidential power and the modern relevance of a statute written nearly 150 years ago.
