Once a National Defense Area has been established, what happens to the area?

The establishment of a National Defense Area (NDA) designates a specific location that is critical for national security and defense purposes. When an NDA is established, it becomes federal land that is typically restricted to essential personnel only. This means that access is controlled rigorously to ensure the protection of the operations and activities conducted within the area.

The designation serves to restrict civilian access and participation, thereby minimizing risks associated with national defense operations. By marking the area as federal land, the government has the authority to enforce security measures that prevent unauthorized entry, ensuring that only individuals with a legitimate need to be present—those deemed "essential personnel"—are allowed on site. This is crucial in maintaining operational security and safeguarding sensitive information or materials.

Therefore, the correct response emphasizes that the NDA transforms into a highly regulated federal territory where access is limited strictly to those with a necessary role in national defense.