In 1959, Wechsler delivered his Holmes lecture at Harvard Law School, "Toward Neutral Principles of Constitutional Law." It was also around this time that Wechsler authored a number of casebooks that changed ideas about criminal law and the federal courts. In 1963, Wechsler's proposed official draft of the Model Penal Code was approved, bringing to a close a decade-long project at the American Law Institute. His wife, Doris Wechsler, noted that he considered the Model Code to be his greatest achievement. Shortly after the approval of the Model Code, Wechsler was named director of the Institute, a position which he held until 1984.