A San Francisco federal judge will hold a landmark bench trial this week to determine whether the Trump administration violated a 19th-century law barring the use of military forces for domestic law enforcement when it sent Marines and California National Guard troops into Los Angeles to respond to immigration protests.

Senior U.S. District Judge Charles R. Breyer, the brother of retired Supreme Court Justice Stephen Breyer, will preside over the three-day trial beginning Monday, marking the first time in U.S. history that the Posse Comitatus Act of 1878, a post-Reconstruction law that prohibits federal military involvement in civilian policing, will be tested in a courtroom.