Not to Lay Tonnage Duties, Keep Troops, Make Compacts, or Engage in War

Article 1 - Legislative
Section 10
Clause 3

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.