No State shall, without the Consent of Congress, lay any duty of Tonnage, keep Troops, or Ships of War in time of Peace, ,b>enter into any Agreement or Compact with another State, or with a foreign Power, or engage in War, unless actually invaded, or in such imminent Danger as will not admit of delay.
My emphasis. This seems to me to be a compact among states, especially since the laws as passed by various states all call for the law to only go into effect after other states have taken a similar action.