Why We Went Looking for National Defense Areas Along the U.S. Southern Border

The Trump administration designated large swaths of U.S. southern border land as national defense areas in spring 2025, enabling military troops to apprehend undocumented immigrants and prosecutors to charge thousands with military trespassing. Prosecutors filed more military trespassing cases in 2025 than in the prior decade combined—at least 4,700 immigrants faced these charges alongside illegal entry counts—yet 60% of resolved cases resulted in dropped or dismissed trespass charges because judges ruled defendants could not be guilty without knowledge they were on military property. The prosecution strategy relies on the argument that illegal border crossing alone proves criminal intent for the military trespass charges, but reporting found that small, sparsely placed signs marked the zones and even federal officials gave conflicting information about exact boundaries. Since the investigation published March 16, prosecutors have filed military trespassing charges in over 1,300 additional cases while the government established new military zones in Arizona, California, and Texas.