ON THE SOUTHWESTERN END of the Tohono O’odham Nation’s reservation... U.S. Customs and Border Protection will soon construct a 160-foot surveillance tower capable of continuously monitoring every person and vehicle within a radius of up to 7.5 miles. The tower will be outfitted with high-definition cameras with night vision, thermal sensors, and ground-sweeping radar, all of which will feed real-time data to Border Patrol agents at a central operating station in Ajo, Arizona. The system will store an archive with the ability to rewind and track individuals’ movements across time — an ability known as “wide-area persistent surveillance.” CBP plans...