John Kennedy actually said...
NOW, THEREFORE, I, JOHN F. KENNEDY, President of the United States, under and by virtue of the authority vested in me by the Constitution and laws of the United States, do command all persons engaged in such obstructions of justice to cease and desist therefrom and to disperse and retire peaceably forthwith;
Context
Executive Order 11053—Providing Assistance for the Removal of Unlawful Obstructions of Justice in the State of Mississippi
09/29/1962