The Guarantee Clause requires the United States to guarantee to the states a republican form of government, and provide protection from foreign invasion and domestic violence. Although rarely formally invoked by Congress, the President, or the courts, there is some consensus on what it means.
At its core, the Guarantee Clause provides for majority rule. A republican government is one in which the people govern through elections. This is the constant refrain of the Federalist Papers. Alexander Hamilton, for example, put it this way in The Federalist No. 57: “The elective mode of obtaining rulers is the characteristic policy of republican government.”
Thus, the Guarantee Clause imposes limitations on the type of government a state may have. The Clause requires the United States to prevent any state from imposing rule by monarchy, dictatorship, aristocracy, or permanent military rule, even through majority vote. Instead, governing by electoral processes is constitutionally required.
However, the Guarantee Clause does not speak to the details of the republican government that the United States is to guarantee. For example, it is difficult to imagine that those who enacted the Constitution believed the Guarantee Clause would be concerned with state denial of the right to vote on the basis of race, sex, age, wealth, or property ownership. Article I, Section 2 of the Constitution left voting qualifications in the hands of the states, although state authority in this area has been altered by subsequent amendments.
The Guarantee Clause also does not require any particular form of republican governmental structure. Thus, in cases such as Pacific States Telephone & Telegraph Co. v. Oregon (1912), the Supreme Court has refused to invalidate various forms of direct democracy permitted by state law, such as popular initiative and referendum, on the ground that they violate the Guarantee Clause. While these decisions were often on jurisdictional grounds, they are consistent with James Madison’s observation in The Federalist No. 43 that “the States may choose to substitute other republican forms.”
It is also clear that federal actions regarding states, authorized by other parts of the Constitution, do not ordinarily violate the Guarantee Clause, even if those federal actions prevent a particular state decision from going into effect. Under the Supremacy Clause, federal law will sometimes supersede otherwise valid state laws.
The question whether a Guarantee Clause challenge may be heard in federal court—that is, whether it is judicially enforceable—is a difficult one. In Luther v. Borden (1849), the Supreme Court held questions involving the Guarantee Clause nonjusticiable, meaning that any remedy for a violation would lie with Congress or the President, not the federal judiciary. Nearly one hundred years later, the Court sweepingly declared that the guarantee of a republican form of government cannot be challenged in court. Colegrove v. Green (1946).
More recently, however, the Supreme Court has left the door open to a Guarantee Clause challenge, intimating that the justiciability of such a claim must be decided on a case-by-case basis. Nevertheless, because protection against invasion or domestic violence is normally available only from Congress and the President, the structure of this section suggests that the political branches have at least the primary duty to carry out its obligations.