() A lawsuit brought by California Gov. Gavin Newsom against President Donald Trump over the deployment of National Guard troops to subdue protests in the state will go to trial Monday. 

The showdown will take place in a bench trial where a judge will examine evidence in the suit challenging the legality of the federal government’s actions in California over the summer.  

Newsom and the State of California filed suit against Trump, Secretary of Defense Pete Hegseth and the Department of Defense over the National Guard being sent to the state to quell protests over immigration raids.

The outcome will be highly consequential as it will carve the extent to which the president can override state leaders with military action in times of unrest.

What’s at issue in the lawsuit?

On June 6, 2025, Immigration and Customs Enforcement began carrying out immigration raids in Los Angeles, which led to city-wide protests.

While Trump called the demonstrations a breakdown of order, Newsom argues that the protests were under control by state forces.

In sending troops to LA, Trump cited Title 10 of the U.S. Code, which allows the president to “call into federal service members and units of the National Guard of any State in such numbers as he considers necessary” when there is a rebellion, an invasion or the danger of either happening.

This order must be issued through a governor, and Newsom did not request troops in LA, the lawsuit argues. It said that there was neither a “rebellion” nor an “invasion,” nor the possibility of either.

Trump’s federal troop deployment is the first without a governor’s request since the Civil Rights Movement and a violation of federal code, according to California’s lawsuit.

Judge Charles R. Breyer, who will hear the case, sided with California in a June 12 ruling that ordered the return of the troops to state control.

 “His [Trump’s] actions were illegal—both exceeding the scope of his statutory authority and violating the Tenth Amendment to the United States Constitution. He must therefore return control of the California National Guard to the Governor of the State of California forthwith.”

What are the arguments on both sides? 

Newsom cites the Posse Comitatus Act, an 1878 law that forbids the U.S. military from participating in civilian law enforcement on U.S. soil.

Exceptions to the Act include enforcement approved by Congress or under circumstances that are “expressly authorized by the Constitution.”

Newsom argues that Trump violated the law and overstepped California’s sovereign authority over the National Guard. 

Trump’s legal team argues the deployment was justified under the Insurrection Act, which can be invoked to suppress rebellion, violence or enforce the law in certain situations. 

At the time of the protests, Trump called protesters “paid insurrectionists” on social media and said demonstrators “should be in jail.”

Newsom argues that the requirements to invoke that law were not met as he did not request federal help. 

‘s Anna Kutz contributed to this story.