Governor Gavin Newsom of California announced that his state plans to file a lawsuit early Monday against Donald Trump for mobilizing the National Guard over the weekend to quell immigration-related protests in Los Angeles.

Experts say it's highly unusual for a president to call up the National Guard when the governor of a state objects. And Newsom is strongly in opposition.

In announcing the lawsuit, Attorney General Rob Bonta called the president's move to federalize the National Guard an "infringement" on state sovereignty.