A landmark trial in California has cast a spotlight on the delicate balance between presidential authority and the legal restrictions governing the use of U.S. military forces in domestic settings. The case, centered on President Donald Trump’s deployment of National Guard troops and active-duty Marines to Los Angeles in June 2025, has raised critical questions about the scope of the military’s role in civilian law enforcement and the effectiveness of existing laws—particularly the Posse Comitatus Act of 1878.
The trial, presided over by U.S. District Judge Charles Breyer in San Francisco, concluded its three-day hearing on August 13, 2025, with a ruling expected in the coming weeks. The lawsuit, filed by California Governor Gavin Newsom, challenges the legality of Trump’s decision to deploy 4,000 National Guard troops and 700 Marines to Los Angeles amid protests against intensified federal immigration raids. Newsom argues that the deployment violates the Posse Comitatus Act, a nearly 150-year-old law that prohibits the military from engaging in domestic law enforcement activities unless expressly authorized by Congress or the Constitution.
The controversy began when President Trump ordered the deployment of federal troops to Los Angeles, citing the need to protect federal personnel and property during protests sparked by Immigration and Customs Enforcement operations. California’s legal challenge contends that the troops exceeded their authority by performing law enforcement functions, such as establishing security perimeters, controlling crowds, and participating in raids—including one at a marijuana farm 100 miles from the city.
The Posse Comitatus Act, enacted in the post-Reconstruction era to prevent military overreach in civilian affairs, reflects a long-standing American tradition of limiting military involvement in domestic governance, rooted in fears of a standing army undermining democratic principles. However, the Justice Department argues that the president’s constitutional authority to protect federal interests overrides these restrictions, and that the troops’ actions do not constitute law enforcement.
During the trial, Judge Breyer pressed Justice Department lawyer Eric Hamilton to clarify the limits of military involvement in domestic affairs. Breyer expressed concern that the Trump administration’s interpretation could allow the military to be deployed almost without restriction, effectively creating a national police force. He also questioned why 300 National Guard troops remain in Los Angeles despite a significant reduction in perceived threats, asking, “What’s the threat today?”
Testimony from U.S. Army Major General Scott Sherman, who commanded the military task force in Los Angeles, revealed that troops were instructed to detain individuals and set up security perimeters whenever federal personnel or property were deemed at risk—even in low-threat situations. California Attorney General Rob Bonta warned that a ruling in favor of the Trump administration could usher in an unprecedented expansion of the military’s role in civilian society, eroding the safeguards established by the Posse Comitatus Act.
The Justice Department countered that California lacks standing to bring the lawsuit, as the Posse Comitatus Act is a criminal statute enforceable only through prosecution, not civil litigation. Breyer, however, raised doubts about the feasibility of criminal enforcement, citing a 2024 Supreme Court ruling granting presidents legal immunity for official acts.
On the same day the trial concluded, Trump ordered 800 National Guard troops to patrol Washington, D.C., in response to what he described as rampant crime—despite data showing a decline in violent crime. This move, permissible due to the president’s broader authority over the capital, further underscored the ongoing tension between federal power and legal constraints on domestic military use.
The trial’s outcome could set a significant precedent for how the military is deployed in California and other states, potentially reshaping the boundaries of executive power. Legal experts, including Steve Vladeck of Georgetown University, note that the lack of clear precedent on the Posse Comitatus Act’s application leaves room for interpretation, making Breyer’s ruling pivotal.
Critics, including the ACLU, have voiced alarm over Trump’s broader domestic military deployments—particularly at the southern border, where National Guard troops have been federalized under Title 10 to support immigration enforcement. These actions, coupled with a Department of Defense directive issued in September 2024, have raised concerns about expanded military surveillance and intelligence operations on U.S. soil.
As the nation awaits Judge Breyer’s decision, the trial has exposed the fragility of legal limits on the military’s domestic role, underscoring the need for clearer reforms to protect civil liberties and preserve the separation between military and civilian authority.
“Breyer was nominated by President Bill Clinton” the outcome is pre-determined.