AS THE FORMER deputy legal director of the ACLU, Jameel Jaffer made many arguments challenging the Obama administration’s drone program over the years, both in and out of court. While those critiques frequently included complex legal challenges, one of them was fairly straightforward. Jaffer would often make the case that even if many people considered President Barack Obama a good and honest man, his bureaucracy for secret killing should not be built on trust alone. Rather, it required publicly demonstrable legality and efficacy — the idea being that those powers would one day be handed off...