On Saturday, the United States, in a joint operation with Israel, killed Iran’s supreme leader, Ayatollah Ali Khamenei. For the first time in the postwar era, Washington has succeeded in killing a foreign leader—shattering a precedent that had been sustained for decades by a mix of moral, political, and logistical concerns. Fifty years ago, in February 1976, President Gerald Ford signed Executive Order 11905, which directed that “no employee of the United States Government shall engage in, or