A bookie (person who organizes gambling} moves his practice from a state where the practice is legal to a state where it is illegal. His move 0 doesn't change GDP because in either case his income is included. 0 necessarily decreases GDP. 0 either increases or decreases depending on whether his gambling income increases or decreases in the new state. 0 necessarily raises GDP. 0 doesn't change GDP because gambling is never included in GDP