Petitioners … were convicted in the District Court of the United States for the Eastern District of New York on eighteen counts of an indictment charging violations of what is known as the “Live Poultry Code,” and on an additional count for conspiracy to commit such violations. By demurrer to the indictment and appropriate motions on the trial, the defendants contended (1) that the Code had been adopted pursuant to an unconstitutional delegation by Congress of legislative power; (2) that it attempted to regulate intrastate transactions which lay outside the authority of Congress, and (3) that, in certain provisions, it was repugnant to the due process clause of the Fifth Amendment. …