The Guarantee Against Invasion Is Unconditional
The three guarantees to the states set forth in Section 4 — to preserve for them a republican form of government, protect against invasion, and protect against domestic violence — are linked by the word “and” that is placed between each of them. Together, the guarantees form what is known in the canons of interpretation and construction as a conjunctive list structured as a polysyndeton.
In any legal instrument, from a constitution to a statute to a contract to a will, each of the individual obligations included in a conjunctive list creates a separate and distinct duty for the obligated party. (See, Scalia & Garner, Reading Law: The Interpretation of Legal Texts, at 116-125 (Thomson/West, 2012).) This means that the binding nature of each separate obligation is independent and does not depend on the extent to which its fulfillment may also help to fulfill other obligations in the list.
Protecting a state against invasion may also help to preserve republican government for the state and forestall domestic violence within its territory. But the obligation of the federal government to protect against invasion is separate, distinct and independent from the other obligations contained in the conjunctive list set forth in Article IV, Section 4. The federal government is obligated to protect each state against invasion in every case, whenever a state is invaded in fact, or threatened with invasion. The duty is unconditional.
The Guarantee Against Invasion Is Fundamental
From the first, the Founders clearly saw that protection against external threats of invasion is a fundamental responsibility of government. Indeed, one of the most important reasons they formed our government was to provide a protective common defense against invasion. As they stated in Article III of the Articles of Confederation:
“The said [thirteen] States hereby severally enter into a firm league of friendship with each other, for their common defense, the security of their liberties, and their mutual and general welfare, binding themselves to assist each other, against all force offered to, or attacks made upon them, or any of them, on account of religion,sovereignty, trade, or any other pretense whatever. (Article III)