Guarantee Clause Law and Legal Definition

Article IV, Section 4 of the U.S. Constitution is popularly known as the guarantee clause. Under this clause the federal government ensures for the states both a republican form of government and protection from invasion or internal insurrection. It says “The United States shall guarantee to every state in this union a republican form of government, and shall protect each of them against invasion; and on application of the legislature, or of the executive (when the legislature cannot be convened) against domestic violence.

Guarantee clause also refers to a provision in a contract, deed, or mortgage by which one person promises to pay the obligation of another.