The Built-In Self-Help Provision in the Constitution to Repel Invasions
Unlike the other two guarantees in Article IV, Section 4, the federal guarantee of protection against invasion is accompanied in the Constitution with an affirmative acknowledgment of the power retained by every state to repel invasions themselves. That power is found in Article I, Section 10, Clause 3 of the Constitution.
Article I, Section 10, Clause 3 states:
“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.” (Emphasis added.)
It is clear that the Guarantee Clause is intended, among other things, to guarantee each and every state federal protection against invasion, and that the current circumstances related to the southern border of the United States would qualify as an invasion from which the federal government is failing to provide its Constitutionally obligated protection. Based upon that conclusion, invaded states may undertake their own efforts to repel the current invasion using their authority to do so under Article I, Section 10, Clause 3 of the Constitution.