Newsom filed a lawsuit Monday in response to Trump ordering the deployment of roughly 4,000 National Guard members to Los Angeles following protests over his stepped-up enforcement of immigration laws. They were originally called in to protect federal buildings, and the president later ordered the deployment of 700 Marines.

The state of California is seeking to stop the president from sending National Guard troops without the governor’s approval.

What the judge rules, and the likely appeals that follow, may alter decades of understanding about the roles of governors and the White House in quelling domestic unrest.