"No State shall, without the Consent of Congress, lay any Duty of Tonnage, keep Troops, or Ships of War in time of Peace, 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."
This scares me a bit. This agreement seems innocuous at first, but the constitution expressly forbids these (and all) kinds of agreements between states for a reason. A small pact like this today could tomorrow become leverage for secessionism or otherwise a power struggle with the federal government.