What is the defense of entrapment?

The defense of entrapment is generally said to be based upon either estoppel or public policy. Sorrells v. United States, 287 U.S. 435, 457, 53 S.Ct. 210, 218 (1932). These concepts can only be called into play when someone has acted at the instigation or behest of the Government in inducing the defendant to commit the crime with which he is charged. My colleagues now propose to make the defense available to defendants whom the Government never sought to entice but who were influenced secondhand by a person to whom alone the Government's inducements were directed. In so holding, the majority have rejected a rule of law that has received the approval of every court hearing criminal appeals in the federal system.