Some pretty interesting comments after the article:
I work on GPS systems. There are effectively 2 versions of GPS. One is an open civilian version. The second one is an encrypted military version, which is more accurate and the important details of the signal are classified. Military drones will use the encrypted version.
Drones like the one spoofed at White Sands Missile Range use the civilian signal exclusively, likely with aiding from an inertial measurement unit.
Spoofing a drone does not mean you hacked into all of the controls and can make it shoot missiles, just that you can make it move where you want. Although, you could try to make it land and take its equipment.