In 1961, at the height of the Cold War, an aviation incident brought Goldsboro, North Carolina, to the brink of a nuclear catastrophe. A B-52 bomber carrying two thermonuclear weapons was soaring through the skies when it broke apart mid-air over private farmlands. One of the bombs underwent all but one of the arming steps for detonation, transmitting a firing signal when it hit the ground.

The Air Force established a secured perimeter around the crash site. Put another way, the military exercised temporary control over the landowners’ property, deciding who could get in and who could leave. The need could hardly have been more extreme; there were nuclear bombs on the site.

The military’s internal guidance for creating restricted areas generally has anticipated scenarios like the Goldsboro incident.

Now a very different reality has emerged. Over the past year, the federal government has stretched the use of what the military has sometimes called “National Defense Areas” (NDAs) beyond all recognition.

In a broadly overlooked but deeply alarming expansion of executive power, the federal government has converted more than 40% of land along the U.S.-Mexico border into restricted military zones. That includes about 110,899 acres that had previously been Bureau of Land Management (BLM) public lands. The establishment of these National Defense Areas along the border is unprecedented.

Through the conversion of such land to military control, the government has developed a scheme of bringing military trespass charges against people crossing the border who unknowingly enter these restricted zones. President Trump’s Department of Justice (DOJ) is aggressively asserting that it should be able to prosecute these individuals – even though federal judges have made clear that the military trespass charges cannot be proven unless someone knew that they were entering an NDA.

With this new phase of militarization of the border, the U.S. government has entered uncharted territory. The implications for fundamental civil liberties are significant. The government may be positioning itself to deter people from arriving at the border in the future. But the government’s approach has been deeply alarming — cutting out Congress, restricting access to huge tracts of once-public lands, and giving federal prosecutors a dangerously overbroad tool for filing criminal charges.