FTA: "Unarmed Predator drones were first used within the United States in 2012, when the Department of Homeland Security flew one over the property of a cattle farmer named Rodney Brossart to surveil him, and to help end a 16-hour standoff between him and another rancher over a stolen-cattle dispute. The use was highly controversial at the time; since then, CBP has used drones hundreds of times, and has not kept very good records about their use."

That strikes me as a highly unexpected and odd situation to be the catalyst for "OK'ing" use within US.