The Department of Interior announced Wednesday it would transfer jurisdiction along most of California’s international border with Mexico to the Navy, establishing a new militarized zone to support border security operations.
The newly designated area extends nearly from the Arizona state line to the Otay Mountain Wilderness, traversing the Imperial Valley and border communities including Tecate. The transfer empowers US troops to apprehend immigrants and others accused of trespassing on Navy installations, with additional criminal charges that can mean prison time.
Expanding Military Strategy
The militarization of border lands was pioneered in April along a 170-mile stretch in New Mexico and later expanded to portions of the border in Texas and Arizona. An April 11, 2025 national security presidential memorandum directed the Defense Department to accept jurisdiction of certain federal lands along the southern border from other agencies.
More than 7,000 troops have been deployed to the border, along with helicopters, drones and surveillance equipment, according to the Associated Press. The deployment follows President Donald Trump’s January 22, 2025 declaration of a national emergency at the southern border.
Interior Department Justification
The Interior Department described the California zone as a high-traffic area for unlawful crossings by immigrants. However, Border Patrol arrests along the southern US border have dropped to the slowest pace since the 1960s this year, amid Trump’s push for mass deportations.
“By working with the Navy to close long-standing security gaps, we are strengthening national defense, protecting our public lands from unlawful use, and advancing the President’s agenda,” Interior Secretary Doug Burgum said in a news release.
In fiscal year 2025, US Border Patrol agents arrested approximately 238,000 people attempting to cross the southern border illegally, according to Customs and Border Protection statistics. March 2025 saw the lowest number of migrant apprehensions ever recorded.
Legal Challenges
The announcement came the same day a federal judge ordered the Trump administration to stop deploying the California National Guard in Los Angeles and return control of those troops to the state.
Trump called up more than 4,000 California National Guard troops in June without Gov. Gavin Newsom’s approval to support immigration enforcement efforts. In September, US District Judge Charles Breyer ruled that the deployment violated the Posse Comitatus Act, an 1878 law prohibiting military use for domestic law enforcement.
However, an appeals court temporarily blocked the judge’s ruling in early December, allowing the federal deployment to continue while the case proceeds. California’s governor and attorney general have challenged the federalization, asking the court to return the California National Guard to state command and control.
Legal Concerns
An emergency declaration by Trump has thrust the military into a central role in deterring migrant crossings between US ports of entry. Legal experts say the strategy flouts the ban on law enforcement by the military on US soil and thrusts the armed forces into a potentially politicized mission.
The California militarized zone follows similar transfers in Arizona (285 acres in Yuma County, July 2025) and New Mexico, where federal prosecutors charged 570 people for unauthorized entry into the military base through early June.
Overview
The Trump administration’s expansion of militarized border zones to California completes a strategy begun in April along New Mexico’s border. While officials justify the transfers as closing security gaps in high-traffic areas, border crossings have fallen to historic lows this year. The military deployment faces ongoing legal challenges over violations of the Posse Comitatus Act, with federal courts split on whether Trump can federalize state National Guard troops without gubernatorial consent.
