California Governor Gavin Newsom is preparing to take legal action if Donald Trump proceeds with plans to deploy federalized National Guard troops to San Francisco — a move the state argues would violate its constitutional authority. Newsom called the proposal a “direct assault on the rule of law,” warning that California will respond immediately through the courts to block what it views as an overreach of federal power.

The dispute centers on whether the federal government can invoke Title 10 to send troops into a state without consent. California officials, including Attorney General Rob Bonta and San Francisco City Attorney David Chiu, maintain that such a move breaches both the Tenth Amendment and the Posse Comitatus Act, which limits federal military involvement in civilian law enforcement.

Trump’s administration contends the deployment could be justified to protect federal property or operations, arguing that the law allows such action when state measures prove insufficient. Legal experts note that precedent is murky — a June 2025 ruling found a prior federalization of California’s Guard unconstitutional, but that decision is still under appeal.

At its core, this battle raises a profound constitutional question: Where does federal authority end and state sovereignty begin? For California, the fight is about preserving control over its Guard; for Washington, it’s about asserting power in the name of security. The outcome could set a lasting precedent — one that defines how far federal intervention can go inside America’s own borders.